Final report Accident prevention systems for lorries �

Accident prevention systems for lorriesThe results of a large-scale field operational test aimed at reducing accidents, improving safety and positively affecting traffic circulation

Fina

l rep

ort

Final report Accident prevention systems for lorries�

Foreword 3

Summary 4

�. Introduction 8

1.1 Background 8

1.2 Organisation 9

�. Research set-up �0

2.1 Generalset-upandreportstructure 10

2.2Set-upoftheFieldOperationalTest 11

2.3 Effectivenessofthesystemsstudied

(researchquestion1) 15

2.4 Effectontrafficsafety

(researchquestion2) 16

2.5 Effectontrafficflow(researchquestion3)16

2.6 EncouragingtheuseofAPS

(researchquestion4) 16

3. Study of the functional effectiveness of the

systems examined �7

3.1 Testtracktesting 17

3.2 Loantest 24

4. Field Operational Test �9

4.1 FieldOperationalTestgeneral 29

4.2 Selectionanddistributionofparticipantsinfield

operationaltest 31

4.3 Dataregistration 34

4.4 Analysisofmeasurements 36

4.5 Datavalidation 38

5. Study of the effect on safety 39

5.1 Literaturestudy 39

5.2 SWOVanalysisofaccidentsintheNetherlands 41

5.3 RelationshipbetweenAPSandsafety 42

5.4 Estimatingtheeffectonsafetyusingamodel46

5.5 Numberofaccidentsobserved 48

6. Study of the effect on traffic flow 49

6.1 Literaturestudy 49

6.2 Model 49

6.3 Trafficfloweffectsasaresultofchange

indrivingbehaviour 50

6.4Trafficfloweffectsasaresultofaccidents54

7. Study of incentives to use APS 56

7.1 Resultsofdriversurveys 56

7.2 APSfromabusinessownerperspective 58

8. Discussion 59

9. Conclusions 6�

Literature 63

Appendix �: Explanatory word list 65

Appendix �: List of hypotheses 69

Appendix 3: Figures showing conceptual models

of traffic flow 73

Appendix 4: Organisation 74

Appendix 5: Analysis of measurements taken during

field operational test 75

Appendix 6: Summary of SWOV report 86

Table of contents

Final report Accident prevention systems for lorries 3

TheMinistryofTransport(FileProof)instructedConnektto

undertakealarge-scalefieldoperationaltestofactivedriver

assistancesystems,socalledaccidentpreventionsystems

(APS),forlorries.

Thisveryspeciallarge-scalestudyinvolvedmorethan

2,400lorriessuppliedby123companies.Thestudylasted

8monthsandoveratotalofaround77millionkilometres

drivingbehaviourwasmeasuredduringnormaldailydriving

onDutchmotorways.Thisfactgeneratedbothchallenges

andlimitationsaswellaslearningexperiencesabout

tacklingsuchlarge-scalefieldoperationaltrialsanddata

processing.Learningexperiencesforwhichthereismuch

(international)interest.

Itisclearthataccidentpreventionsystemsfittedperfectly

inthedailyoperationofahaulier.Therobustsystems

contributepositivelytothefeelingofdrivingsafelyandthe

professionalismwithwhichthedriverperformsthedriving

task.

Thattherearealsoothereffectsondrivingbehaviour,traffic

flowandsafetythanexpectedinliteratureorbyexperts

isbothsurprisingand,ontheotherhand,possiblyakey

influenceontheveryheavytrafficintheNetherlands.

Morereason,therefore,toemphasisethedrivingtaskin

thefuturealongwiththerelationshipbetweenthesurroun-

dingsandthedriver,ofwhichthereappearstobeverylittle

knowledge.

Followingthisfieldstudythenumberofaccidentpreven-

tionsystemsintheDutchmarkethasvirtuallydoubledand

morethan120companieshavehadexperienceofthem.A

significantsepforward.

Almosteveryparticipatingcompanyhasindicatedthatitwill

continuetouseaccidentpreventionsystemsafterthestudy.

Atthismoment(September2009)sevencompanieshave

alreadystatedthattheywillextendtheuseofaccidentpre-

ventionsystemstolorriesnotcurrentlyequippedwiththem.

Connektthankseveryonethatcontributedtothisvery

specialfieldstudy,thisreportandthetheirconstructive-

nessinthisstudy:membersoftheCoreTeam,theScientific

SoundingBoard,theAdvisoryGroupinwhichalltransport

sectorswererepresented,theSWOVand,ofcourse,all

participatingcompanies.

Nico Anten

Managing Director, Connekt/ITS Netherlands

Foreword

Final report Accident prevention systems for lorries4

In2008and2009ontheinstructionsoftheMinistryof

Transport(FileProof),Connektundertookalarge-scalefield

operationaltestofactivedriverassistancesystems,socalled

accidentpreventionsystems(APS),forlorries.Overeight

monthsfivedifferentaccidentpreventionsystemsanda

registrationsystemweretestedonDutchmotorways.

Large-scale field operational test

Itisnotaneasytasktomeasuredirectlytheeffectsofan

APSonthenumberofaccidentsorontrafficflow.Evena

large-scalestudyinvolvingmanyhundredsorthousands

oflorriesisinadequate.However,theeffectsofanAPS

ondrivingbehaviourforalargenumberoflorriesover

anextendedperiodcanbemeasuredinalarge-scalefield

operationaltest.Usinggenerallyavailableknowledge,those

effectscanthenbetranslatedintoeffectsontrafficflowand

safety.Beforesuchalarge-scaletestcanbecarriedout,itis

necessarytoestablishwhethertheselectedsystemsfunction

asintended.

Sincerelativelyfewsystemsareinoperationinthe

Netherlands,suchatestwillhavesignificantinfluenceon

theexperienceswithandacceptanceofthesesystemsby

hauliersanddrivers.

Research questions

Thestudywasthereforestructuredalongthefollowing

lines:

a. Howeffectivearethesystemsstudied?Dothey

correctlydetectthe(hazardous)situation?Dothey

warnthedriverproperlyandintime?Andifactive

systemsintervene,dotheydosoproperly?

b. WhatistheeffectontrafficsafetyifAPSareusedbya

(large)portionoflorriesdrivingontheDutchroad

network?

c. WhatistheeffectontrafficflowifAPSareusedbya

(large)portionoflorriesdrivingontheDutchroad

network?

d. Canthegovernmentactasstimulatortoencourage

useofAPS?

Accident prevention systems

Theaccidentpreventionsystemsselectedforthefieldstudy

are:

Adaptive Cruise Control (ACC)

• ACCmaintainsthepresetspeedandadaptsthisto

maintainapresentheadwaydistanceifthepreceding

vehicleisslowerorotherroadusermergeswiththe

lane.

Lane Departure Warning Assist (LDWA)

• LDWAwarnsthedriverifhethreatenstobreachthe

lanemarking(withoutusinghisindicator).

Forward Collision Warning/Headway Monitoring &

Warning (FCW/HMW)

• FCWwarnsthedriveriffrontalcollisionisimminent;

HMWwarnsthedriverintheeventoftheheadway

distancebeingtooshort.Thesesystemsweretestedas

integratedpartsofasingledevice.

Directional Control/Roll over Control (DC/ROC)

• DC/ROCdetectssituationsinwhichthesteerabilityof

avehicleisendangeredandcorrectsthisbyabrake

interventionononeofthewheels.

Summary

Final report Accident prevention systems for lorries 5

Black Box Feed Back (BBFB)

• BBFBgivesthedriverfeedbackaboutthedriving

performancecomparedwithothersintermsof:

- Changesinspeed(consistentorinconsistent

drivingbehaviour);

- Harshbraking(significantdelay);

- Useofcruisecontrol;

- Fuelconsumption.

Inventory

Intheautumnof2007aninventorywasmadeofthe

populationofAPS(excludingBBFB)intheNetherlandsat

thatmomentintime.Itcametoatotalofaround1,500

systems,90%ofwhichweretheDirectionalControltype,

ananti-rolloversystemmuchusedincontainerlorries

transportinghazardousgoods.Tocarryoutarepresentative

fieldoperationaltestofadequatescale,extrahauliershad

tobefoundinordertohaveanumberofdifferentaccident

preventionsystemsbuiltintonewlorries.Thetotalnumber

ofsystemsthusincreasedbyaround1,600.

Functional effectiveness of the systems

studied

Theabovementionedaccidentpreventionsystemswere

firstlytestedonatesttracktoanswertheinitialquestion

relatingtothefunctionaleffectivenessofthesystems.The

conclusionofthetesttracktestswasthattheactivedriver

assistancesystems(subdividedintointervening,informing

andfeedbacksystems)werefunctionallyeffective.Theydo

whattheyhavetodo:detectreliably,warnthedriverand

intervenewherenecessary.

Field operational test

FortheFieldOperationalTest(FOT)around2,400lorries

wereequippedwithdataregistrationsystemstoenable

drivingbehaviourtobemonitoredandmeasured,and

thesesystemsweredividedintodifferentgroups,including

areferencegroup,dependingonthetypeofAPS.The

referencegrouphada‘silent’system,whichmeansthat

whilethedriverwasnotinformeddataweremeasured.The

driversinthereferencegroupknewtheywerepartofthe

test.Thelorriesweremonitoredforeightmonthsonthe

Dutchmotorwaynetworkoveratotaldistanceofabout77

millionkilometres.Around300lorriesgeneratednodataat

onetimeoranotherduetovariousreasons,suchastech-

nicalproblemsorstoppages.Notalllorriesweremonitored

foreightmonths.Thesystemswerenotremovedafterthe

measurementsbutremainthepropertyoftheparticipating

companies.

Measurements

Thefieldstudymeasurementsrevealthatdriverassistance

systemsoraccidentpreventionsystemshaveaneffect

onhowthedriverperformshisdrivingtask.Thesystems

reducetherisksofaccidentstoagreaterorlesserdegree,

withthekeyindicatorsbeing:

• LongerheadwaytimeswiththeuseofACCandFCW/

HMW;

• LowerrolloverriskswiththeuseofDCandROC;

• Drivinglessclosetotheprecedingvehiclewiththeuse

ofACC;

• Fewerunintendedlanebreachingwiththeuseof

LDWA;

• MoreconsistentdrivingwiththeuseofBBFB.

Driverquestionnairesconfirmthispicture.

Summary

Final report Accident prevention systems for lorries6

Asecondresultofthemeasurementsisthatjustfiveacci-

dents(withjustmaterialdamage)wereregisteredduring

themeasuringperiodandallfivewereinthereference

groupwherebythedriverwasnotassistedbyanAPS.That

isclearlylowerthanthe16-19accidentsfortheentirefield

operationaltest(or6forthecontrolgroup)thatwouldon

averagebeexpectedbasedonthekilometresdrivenorthe

sizeofthegroup.Thislownumberofregisteredaccidents

isnotpredictedbasedonthebasisofthemeasurementsof

theeffectsofAPSinthefieldoperationaltest.Thefactis

thatthoseeffectsarenotsignificantenoughtoexplainsuch

adifference.Inordertogainabetterexplanationitis

recommendedthatthisgroupismonitoredforalonger

periodinrespectofthenumberofaccidentscaused.

Effect on traffic safety

Theliteraturecontainsreportsinwhichquantitativeverdicts

aremadeabouttheincreaseintrafficsafetywhenAPSare

appliedonalargescale.Thequalityofthemodelsand

causallinks,however,fallshortandthustheverdictsneed

tobetreatedwithacertaindegreeofcaution.Inother

words,thesecondresearchquestioncannotbeanswered

bymodelsandlinkstoliterature.Amodelhasthusbeen

developedtoenableapredictiontobemadeaboutthe

effectontrafficsafety,usingdatafromthefieldstudy,

despitethelimitations.Thoseestimatesindicatethatthe

activeinterventionsystemsACCandDC/ROCcanbe

expectedtohavemoreimpactthanothersystems.

Effect on traffic flow

TheeffectofAPSonthetrafficflowwaspredictedusinga

trafficflowmodelcomposedonthebasisofliteratureand

expertmeetings.Thedirecteffectontrafficflowisminor

sincehardlyanysignificantdeviationsoftheaveragespeed

andheadwaytimecouldbedemonstratedbetweenvehicles

containingactiveaccidentpreventionsystemsandthe

referencegroup.Theindirecteffectbyavoidingaccidents

willbepresent,however,butisdifficulttoquantify.The

magnitudewillalwaysbelimitedgiventheverymodest

share(approx.1.6%)ofthelostvehiclehourscausedby

accidentsinvolvinglorries.

Driver experiences

Consultationamongplayersinthemarketanddriver

questionnairesrevealthatthesesystemsarevaluedbythem

inpractice,providedthattheyaresetupinharmonywith

practice(preventionofexcessivewarning).Thesystems

contributepositivelytotheperceptionofsafedrivingand

theprofessionalismoftheperformancebythedriverof

hisdrivingtask.ACCisparticularlyexperiencedaspositive

andtherobustnessofallsystemsconsideredmorethan

adequate.

Virtuallyalltheparticipatingcompanieshaveindicateda

desiretocontinueusingthesesystemsaftertheendof

thetest.Sevencompanieshaveindicatedthattheywill

extenduseofAPStolorriesnotcurrentlyequippedwith

thesystem.

Summary

Final report Accident prevention systems for lorries 7

Conclusions

Indicationsarestrongthatpeopledriveveryclosebehind

oneanotheronDutchmotorways(0.5to1.5sat80km/u).

Becausemaintainingdistancetotheprecedingvehiclein

busytrafficisakeycomponentofthedrivingtask,the

measurementssupportthetheorythat:

• ACCcandirectlyalleviatethetaskofmaintaininga

safedistanceandFCW/HMWcansupportthistask;

• DCandROCactivelypreventcriticallimitsfrombeing

exceeded;

• LDWAhelpspreventunintendedlanebreaches,

providedtheset-upissuchthattheattentionofthe

driverisnotdistractedfromhismaindrivingtask;

• BBFBensuresamoreconsistentdrivingbehaviour

providedthesocialembeddingofthefeedbackis

properlycateredfor.

Recommendations

ItisrecommendedthatboththegroupusingAPSandthe

referencegrouparemonitoredforalongerperiodandto

continueregisteringthenumberofaccidentstoseewhether

thenumberofaccidentsremainsaslowasmeasuredfora

longerperiod.

Itisrecommendedtocontinueprovidingincentivestouse

APSnowthatacriticalmasshasbeenachievedandpositive

experiencegained.TheamountofdatacollectedintheFOT

ishuge.Itisrecommendedtomakethedatasetavailableto

thirdpartiesforfurtheranalysis.

Insubsequentresearchitisrecommendedtodelvedeeper

intotherelationshipbetweenengineeringsystemsand

behaviouraswellasdriverreaction.Literaturestillprovides

toolittleinsightintohowdriversupportsystemscanleadto

modifiedbehaviour.

Summary

Final report Accident prevention systems for lorries8

�.� Background

Freighttrafficin2007accountedfor15%ofalltrafficon

Dutchmotorwaysandinthesamepercentageoffatalities

onDutchmotorwaysfreighttrafficwasinvolved.Freight

trafficaccidentsoftenhaveadisruptiveeffectontrafficflow

ontheroadnetworkandgeneratelongtrafficjams[15].

OnDutchmotorwaysin2007some1.1millionvehicle

hourswerelostduetolorryaccidents.Thisfigureamounts

toapprox.1.6%ofthetotalnumberofvehiclehourslost

ontheDutcharterialroads.

InastudybyDHV[31]adifferenttrafficflowgaugewas

used,namelythetrafficjamseverity(timexlength);1.45%

oftheentiretrafficjamseveritybetween2000and2005

wasattributabletolorryaccidents.

Boththeabsoluteandrelativesizeoffreighttrafficare

expectedtocontinuerisinguntil2020.Asitdoesso,the

MinistryofTransportandthetransportsectorwillfacea

challenge,namelyhowtoenableefficientroadtransport,

improvesafetyandboosttrafficflow.Useofmoderntech-

nology,likedriversupportsystemsoraccidentprevention

systems(APS)canassisthere.

Forthisreason,theMinistryofTransportinstructed

Connekt/ITSNetherlandstoconductabroadlystructured

fieldoperationaltesttomeasuretheeffectsofaccident

preventionsystemsinpractice.Theaimofthefieldopera-

tionaltestwastogainbetterinsightintotheextentto

whichthesesystemscanaidtrafficsafetyandtrafficflow

ontheDutchroadnetwork.Todatethesesystemshave

onlybeenanalysedtoalimiteddegree.

Theaimofthefieldoperationaltestwastranslatedduring

theoperationintofourresearchquestionsthatareconside-

redinchapter2‘Researchstructure’.

Thefieldoperationaltestwouldtestfiveseparatesystems

intendedtopreventaccidentsinvolvinglorries.Thesystems

werebuiltintoalargenumberoflorries.Aregistration

systemrecordeddriverbehaviour.Theeffectsofthese

sophisticatedsystemsweremeasuredoveraneight-month

period.

The‘Accidentpreventionsystemsforlorries’projectisone

ofmorethan60projectsrunby‘TacklingTrafficJamsinthe

ShortTerm’(FileProof)thattheMinistryhasconductedwith

aviewtoreducingthenumberoftrafficjamsintheperiod

2006-2009.

Inthefirstquarterof2006,attheMinister’srequest,

Ministrystaffconsiderednewoptionsforreducingtraffic

jamsusingrelativelysimplemeansandintheshortterm.

Numerouscreativeideaswerealsoproposedbycentral

government,tradeandindustry,interestgroupsand

knowledgeinstitutes.Intotal,thefeasibilityofalmost3,000

ideaswasassessedbyexternalexperts.Thisresultedina

Ministry-wideprogrammeinvolvingsome60projectstaking

ashort-termapproachtoresolvingtrafficjams.Theproject

‘Accidentpreventionsystemsforlorries’wasoneofthese

60projects.Thecategorytowhichitbelongsisentitled

‘Projectstoreduceincidentaltrafficjams’.

�. Introduction

Final report Accident prevention systems for lorries 9

�.� Organisation

TheclientoftheAPSprojectwastheMinistryofTransport

(FileProof),withDGMobilitydelegatedascustomerand

supervisor.

FileProofrequestedConnekttoconductthisproject.

Connektisapublic-privatenetworkconsistingofgovern-

mentbodies,privatecompaniesandknowledgeinstitutes.

Itconnectsparties,enablingthemtoworkinmutualtrust

toachievetheenduringimprovementofmobilityinthe

Netherlands.Theprojectmanagementwasperformedby

Connekt.

AsmaincontractorappointedbytheMinistryofTrans-

port(FileProof),Connektoutsourcedsomeoftheproject

performancetotwopartiesselectedbytheMinistry:TNO

andBuckConsultantsInternational(BCI).TNOisaDutch

researchinstitutethatappliesscientificknowledgewiththe

aimofstrengtheningtheinnovativepowerofindustryand

govern-ment.BCIisanindependentinternationalresearch

andconsultancyagencythatresearches,advisesand

conductsprojectmanagementinthefieldsofeconomics,

space,infrastructure,propertyandlogistics.

Together,representativesoftheMinistryofTransport,

Connekt,TNOandBuckConsultantsInternationalformed

theCoreTeam.

TheDutchnationalroadsafetyresearchinstitute(SWOV)

madeitstrafficsafetyknowledgeavailabletofurthersub-

stantiatetheintrinsicbackgroundinthisfield.

ThemanagementofConnektdiscussedaprogressreport

eachquarterwiththeFileProoforganisation.

InadditiontotheCoreTeam,whichwasresponsiblefor

theresult,aScientificSoundingBoardgroupwassetupto

safeguardthequalityoftheresearch.Thisgroupconsisted

ofSWOV,theUniversityofTwente,TUDelft,RWS-DVS,

FileProofandAskary.Furthermore,anumberofcoordina-

tingorganisationswereinvolvedinthefieldoperationaltest

intheroleofAdvisorygroup(TLN,BOVAG,KNV,EVO,

VERNandtheRAIAssociation).

Inaddition,themarketwascloselyinvolvedintheproject,

forexample:

• Suppliersofdriverassistancesystemsandmeasuring

equipment:CliffordElectronicsincooperationwith

OctoTelematicsandCarrierWeb;

• Ateamof75specialistsanddealersabletofit

factory-fitandretrofitsystems;

• LorrysuppliersintheNetherlands:DAF,Volvo,Scania,

MAN,Mercedes,IvecoandRenault(unitedunderthe

RAIAssociation);

• Dozensofdealersinadealernetwork(unitedunder

BOVAG);

• 2,400vehiclesownedby123participatingtranship-

mentcompaniesandhauliers.

�. Introduction

Final report Accident prevention systems for lorries�0

�.� General set-up and report structure

TheaimoftheAPSprojectwastodevelopunderstanding

oftheextenttowhichaccidentpreventionsystems(APS),

alsoknownasdriverassistancesystems,whenusedona

largescalecancontributetotrafficsafetyandtrafficflowon

Dutchroads.Thiswastobeachievedbymeansofawide-

rangingFieldOperationalTestorFOT.

Itwasnotpossibletomeasuredirectlytheeffectsofan

APSonthenumberofaccidentsorthetrafficflow.Evena

large-scaletestinvolvingmanyhundredsifnotthousandsof

lorrieswouldbetoosmalltoachievethis.Whatalarge-

scaletestdoesenable,however,isthemeasurementofthe

effectsofanAPSonthedrivingbehaviourofalargenum-

beroflorriesoveralongerperiod.Onewouldexpectitto

bepossible,withtheaidofgenerallyavailableknowledge,

totranslatetheseeffectsintoeffectsontrafficflowand

safety.

Inthisreport,theword‘effectiveness’isabroadconcept.

Forthisreason,asubtledistinctionhasbeenintroduced

intothisstudy.TheAPSthatweretestedwererequiredto

correctlydetectthe(hazardous)situation,toalertthedriver

correctlyandintimeand/ortointervenethemselvesinthe

correctmanner.Theextenttowhichasystemsatisfiesthis

requirementisindicativeofitsfunctionaleffectiveness;the

systemdoeswhatitissupposedtodo.

Forsystemsthatinform,thedriver’sbehaviour(andreac-

tion)followingasystemalertisofimportance.Ifadriver

(hypothetically)ignoresasystem’sreportsrepeatedly,even

aperfectlyfunctionallyeffectivesystemwillnotbeableto

contributetothetrafficsafetyortrafficflow.Wereferto

theextenttowhichthesystembringsaboutanadaptation

(eithermomentaryorpermanent)inthedriver’sbehaviour

(andreaction)asthedegreeof‘behaviouraleffectiveness’.

Theultimateeffectivenessofasystemwithregardtosafety

andtrafficflowwilldepend,therefore,on(1)thesystem’s

functionaleffectiveness,(2)thesystem’sbehaviouraleffec-

tiveness,and(3)anyotherdeterminants.Inthistestitwas

notpossibletomeasurethisbehaviouraleffectiveness.

Inthistestwehavelimitedourselvestomeasuringthe

vehiclebehaviour.

Theresearchwasstructuredaroundthefollowingprimary

questions.

Researchquestion1:

Howeffectivearethesystemsstudied?Dotheydetect

the(hazardous)situationcorrectly?

Dotheywarnthedrivercorrectlyandintime?

Andiftheinterveningsystemsareactiveones,dothey

dothisinthecorrectmanner?

Howthefunctionaloperationofthesystemswastestedon

atestcircuitisdescribedinchapter3.

Alargenumberoflorrieswasequippedwithvariousacci-

dentpreventionsystems.Inadditionareferencegroup

equippedwitha‘silent’system.Inthereferencegroup,the

driverswerenotinformedbythesystembutweremeasu-

red.Subsequently,thelorrieswerefittedwithdataregistra-

tionsystemsandtrackedoveralongerperiod.

1 Many aspects influence driving behaviour. Therefore it is unclear how the behavioural effectiveness of a warning signal should be monitored.

�. Research set-up

Final report Accident prevention systems for lorries ��

Howthegroupswerecompiledandwhatwasmeasuredby

thedataregistrationsystemsispresentedinchapter4.

Researchquestion2:

WhatistheeffectontrafficsafetyifAPSisusedbya

(large)proportionofthelorriesdrivingontheDutch

roadsystem?

Researchquestion3:

WhatistheeffectontrafficflowifAPSisusedbya

(large)proportionofthelorriesdrivingontheDutch

roadsystem?

Withtheaidofmodelstakenfromtheliterature,the

measuredeffectsofanAPSweretranslatedintopredictions

aboutthechangeintrafficsafetyandtrafficflow(presu-

minglarge-scaleapplication).

Theeffectsontrafficsafetyarediscussedinchapter5and

inchapter6,theeffectsontrafficflow.

Sincerelativelyfewaccidentpreventionsystemswere

operationalintheNetherlandsatthestartofthetestin

2008,theFOTwillhavehadconsiderableinfluenceonthe

hauliers’anddrivers’experienceofthesesystemsandtheir

acceptanceofthem.Forthisreason,afourthquestionwas

addedinconsultationwiththeclient.

Researchquestion4:

Canthegovernmentadoptarolethatencouragesthe

useofAPS?

Theresultsofthedriversurveysandtheinterviewswiththe

participatingcompaniesarepresentedinchapter7.

Fromtheresearchpointofview,afieldoperationaltestisby

definitionnotidealsincefieldconditionsareoftenuncon-

trollable.

Discussedinchapter8aretheresultsandtheobserved

phenomena.

Chapter9containstheconclusions.

�.� Set-up of the Field Operational Test

Anearlierstudy[11]examinedwhichaccidentprevention

systemscouldbeusedinalarge-scalefieldoperationaltest.

Someofthesesystemscanbeincorporatedinexistinglor-

riesaftertheyhaveleftthefactory(retrofit),otherscanbe

factory-fittedonly.Thismeansthesystemmustbesupplied

aspartoftheorderforanewlorrysubmittedtothemanu-

facturer,alsoknownasanOriginalEquipmentManufactu-

rer(OEMs).

Furtheraspectsoftheset-upconcerningthesizeofthe

randomsurveyandregistrationmethodologyarepresen-

tedin[30].Inorderforthemeasurementdatainafield

operationaltesttosupportstatisticallysoundjudgements,it

isnecessarythateachgroupofaccidentpreventionsystems

hassufficientlorries.Thesmallerthepossibleeffect,the

largerthegroupmustbetoenablereliablejudgements.

Anidealsizeis400lorriespergroup,butsomesoundjud-

gementscanalsobemadewithconsiderablylowernumbers

(morethan50).

�. Research set-up

Final report Accident prevention systems for lorries��

In2007apollwascarriedoutamongsuppliersofsystems

thatcanberetrofittedandmanufacturersofsystemsthat

canbefactory-fittedtoestablishthethencurrentpopula-

tionofAPS(excludingtheso-calledBlackBoxFeedback

system)intheNetherlands.

Thetotalnumberofsystemswasroughly1,500,ofwhich

90%wereofthetypeDirectionalControl,ananti-rollover

systemmuchusedintankerscarryinghazardousgoods.

AccordingtoindicationsgivenbytheOEMs,thepicturefor

factory-fittedsystemsisnodifferentintherestoftheEU.

Asignificantmotiveamongtankerhauliersistherequire-

mentinGermanyforcertaintypesoftankertransportto

carryanAPS.

However,thatnumberwastoosmalltoprovidethebasis

forafieldoperationaltest.

Threeissuesdeterminedthetermofthefieldoperational

test:

• Thedeliveryoffactory-fittedsystemsinnewlorries,

theincorporationandtestingoftheretrofitsystems;

• Theconstruction,testingandoperationofthedata

registrationsystemsonthisscale;

• Thevalidationandprocessingofthemeasurement

dataobtainedwiththesystems.

Thisledtothechoiceto:

• Testfourtypesofcommerciallystandardandeasily

obtainableAPSinthetest,supplementedwithafeed-

backsystemthatmayalsohaveaneffectontraffic

safetyandtrafficflow.

• Useexistingdataregistrationsystems.

Togetherwithsuppliers,manufacturersandhauliersa

populationultimatelytotallingmorethan2,400lorrieswas

compiledforinclusioninthetest.Thisisapprox.1%ofthe

totalpopulationoflorriesintheNetherlands.

TheAPS-testprojectteammadenosmalldemandsupon

thehauliersandtheirdrivers.Forexample,theretrofittingin

agaragetookonaveragefourhours,vehiclesweresome-

timesrecalledforrepair,thesoftwarehadtobeconfigured,

andthedriverswerealsotrackedandquestionedabout

theuseofthesystems.Tocompensateforthedisruptionto

dailybusinessoperations,thesystemswereretrofittedfree

ofchargeaspartofthetest.Followingtheconclusionofthe

test,thedataregistrationsystemsbecamethepropertyof

thehaulagecompanies.

�. Research set-up

Final report Accident prevention systems for lorries �3

Thefollowingtypesofsystemswereselectedforthefield

operationaltest:

FCW/HMW(ForwardCollisionWarning/HeadwayMonito-

ringandWarning,seeFigure1).

Thesystemconsistsofacameraandprocessingunit,a

displayandspeakers.Thewarningisissuedbothasasound

andasanimage.Itispresentedinphases.

FCWissuesawarningiftheheadwaytime(TimeToCol-

lision/TTC)becomestoosmall.TheTTCisdefinedasthe

distancetothevehicleinfrontdividedbythedifferencein

speed.Thestandardsettingis2.7sec.

HMWissuesanalertassoonasthevehicleapproachestoo

closelythevehicleinfront.ThewarningsissuedbyHMW

comeinfoursteps:

• Exceeding2.5seconds grey

• Between1.1and2.5seconds green

• Between0.7and1.1seconds orange

• Lessthan0.7seconds red

Thesystemworksatanyvehiclespeed.Thesettingsshown

abovewereusedinboththetesttracktestsandthefield

operationaltest.Inthefieldoperationaltestthedrivercould

disengageneithersystem.Thesystemcanberetrofitted.

LDWA(LaneDepartureWarningAssist,seeFigure2).

Thissystemsimilarlyconsistsofacameraandprocessing

unit,adisplayandspeakers.LDWAcanbeanadditio-

nalfunctionalityofanFCW/HMWsystem.Inthisfield

operationaltesttheMobileyesystemproducedbyClifford

ElectronicswaschosenastheLDWAsystemand/orFCW/

HMWsystemtoberetrofitted.Thissystemalertsthedriver

whenanunintentionallanedeparture(withoutuseofthe

indicator)isimminent.

�. Research set-up

Figure 1: Forward Collision Warning/Headway Monitoring and Warning - Source: Clifford Electronics Figure 2: Lane Departure Warning Assist

Safe distance Short distance Dangerous distance

Final report Accident prevention systems for lorries�4

Thedriverisinformedbya‘rumblestrip’noiseontheside

onwhichthelinecrossingisimminentaswellasbyavisual

warning.ImminenceisestablishedusingaTimeToLine

Crossingcriterionthat,usingacamera,determineshow

muchtimeremainsbeforealinecrossingoccurs.Asystem

requirementisthatsufficientgoodlinemarkingsarevisible

ontheroad.

TheretrofitLDWAsystemproducedbyMobileyehasthe

followingcharacteristicsettings:

• Becomesactiveatspeedsinexcessof55km/hr,and

becomesinactiveoncemoreifthespeeddropsbelow

50km/hr.

• WarningforaTimetoLineCrossing(TTLC)of0.5

seconds.

• Afterawarning,thenextwarningwillbegivenonly

ifthevehiclehassincereturnedtoitslaneandthe

distancetotheroadlineismorethan0,3m(toavoid

overuseofthealarm).

• Nowarningifindicators/alarmlightsareoperational.

Liketheothersystems,thissystemcouldnotbedisengaged

bythedriverinthistest.Thesystemcanberetrofitted.

ACC(AdaptiveCruiseControl,seeFigure3).

Likeacruisecontrolsystem,ACCmaintainsthevehicleat

aspeedchosenbythedriver.Inaddition,thesystemkeeps

aneyeonthevehicleinfrontusingaradarorsimilarsensor.

Theheadwaytimetothevehicleinfrontismaintained

automaticallyatasafelevel;theACCcanaccommodate

thisbyreducingthespeedofitsownvehicle.

Thesystemisavailablefactory-fittedonlyandforthistest

thesettingswerenotadjusted.Inthetestthedriverwas

abletoadjustthesettingasrequiredandtodisengagethe

system.

DC/ROC(DirectionalControl/RollOverControl,seeFigure

4).DCisasystemthatautonomouslytakesactionifthe

vehiclenolongerrespondswelltosteeringmovements

orstartstoslip.Normallythisisachievedbyapplyingthe

brakesselectivelytosomeofthevehicle’swheels,some-

thingthedrivercouldneverdo.DCcanbeeasilycombined

withRollOverControl(ROC),whichhasasimilaroperating

principleandwhichattemptstopreventthevehiclefrom

rollingover.Thesystemisavailablefactory-fittedonlyand

cannotbeswitchedoff.

�. Research set-up

Figure 3: A box lorry with ACC following a preceding vehicle - Source: MAN Trucks Figure 4: DC brake intervention in oversteer and understeer situations

Oversteer situation Understeer situation

With

out

DC

With

DC

Final report Accident prevention systems for lorries �5

BBFB

TheBlackBoxFeedBacksystem(BBFB)isafeedbacksystem

relatedtodrivingbehaviour.ItisproducedbyCarrierWeb.

Informationaboutthedriver’sdrivingbehaviourisretrieved

fromthestandard-fitinterfacesinlorriesbytheMotorMa-

nagementSystem(BlackBox).Theinformationisfedback

tothedriverandthefleetmanager.

Figure5showsanexampleoftheinformationreceivedby

thedriverfromtheBBFBsystem.

Theinformationreceivedbythedriverincludes:

• Changesinspeed(constantdrivingbehaviourornot);

• Harshbrakingactions(considerabledelay);

• Useofthecruisecontrol;

• Fuelconsumption.

Foreachvariablethedriverreceivesinformationabouthis

resultsforthedayandthepastweeks.Moreover,theresults

canbecomparedwiththoseofthedriver’sownlong-term

averageandwithcolleagues’results.

�.3 Effectiveness of the systems studied

(research question �)

Theeffectivenessofthesystemswasdeterminedinatwo-

partprocess:

Thefirstpartinvolveddeterminingthefunctionaleffective-

nessofthesystems:

Dotheydetectthe(hazardous)situationcorrectly?Dothey

warnthedrivercorrectlyandintime?Andifthesystems

interveningareactiveones,dotheydothisinthecorrect

manner?

Thebehaviourofthesystemswastestedsystematicallyon

aclosedtestcircuitwiththeaidofarefinedandaccurate

measuringsystem.Thismeasuringsystemwasmuchmore

preciseandextensivethanthosethatcanbeusedinalarge

fieldoperationaltest(FOT)totracklorries.Thismeasure-

mentprovideddetailedinformationaboutthebehaviourof

thesystems.

Thesecondpartconsistedofthefieldoperationaltestin

whichlorriesintheFOTweretrackedoveralongerperiod

ofeightmonths.Thebehaviourofthesystemsandthe

�. Research set-up

Figure 5: Information in the BBFB screen - Source: CarrierWeb

Final report Accident prevention systems for lorries�6

vehicleweremeasuredandcollectedaspartofday-to-day

activities(albeitwithalessrefinedmeasuringmethodthan

onthetestcircuit).

Inthetestcircuitthetestingofbehaviouraleffectiveness

(doesthedriveradapthisdrivingbehaviourasaconsequen-

ceofthesystems)wasnotmeasured.Inthefieldoperatio-

naltestaderivativeofthiswasmeasured,namelyhowthe

vehiclebehaved.

AstheeffectofDC/ROCintheFOTcouldbemeasured

onlytoalimitedextent,anextraloantestwassetupspe-

cificallyforthisgroup.AlorryequippedwiththeseAPSand

withthefullrangeoftestcircuitmeasuringinstrumentation

wasloanedoverseveralweekstovarioushauliers.

�.4 Effect on traffic safety

(research question �)

Theeffectontrafficsafetyofthelarge-scaleuseofanAPS

canbederivedfromfoursub-researchstudies:

• LiteraturestudyoftherelationshipbetweenAPSand

trafficsafety;

• AnalysisoftheaccidentsintheNetherlandsinvolving

lorries:onwhichtypeofaccidentwouldsucha

systembeabletohaveapreventiveeffect/orbe

abletoreducethechanceofandextentofthebodily

injury?

• Analysisofthemeasurementresultsobtainedinthe

FOT;

• Developmentofaconceptualandquantitativemodel

withwhichapredictioncanbemadeaboutthe

effectsontrafficsafety,assumingthemeasurement

resultsobtainedintheFOT.

�.5 Effect on traffic flow

(research question 3)

Theeffectontrafficflowofthelarge-scaleuseofAPScan

bederivedfromfoursub-researchstudies:

• LiteraturestudyoftherelationshipbetweenAPSand

trafficflow;

• AnalysisofthetrafficfloweffectsrelatedtoAPSin

lorries;

• Analysisofthemeasurementresultsobtainedinthe

FOT;

• Developmentofaconceptualandquantitativemodel

withwhichapredictioncanbemadeabouttheeffects

ontrafficflow,assumingthemeasurementresults

obtainedintheFOT.

�.6 Encouraging the use of APS

(research question 4)

Asaneffectofthelargefieldoperationaltest,alargenum-

berofdriversandhauliersgainedfieldexperienceofusing

APS.

Theirexperienceisdeterminingwhetherandhowthe

governmentcancontinuetoencouragethewideruseof

APSinitsroleas‘encouragingparty’.Inordertocollect

theseexperiencesandtotestthemeasurementresultsof

thefieldoperationaltest,driversurveysandcompanyinter-

viewswereheldattheendoftheFOT.

�. Research set-up

Final report Accident prevention systems for lorries �7

3.� Test track testing

IntheperiodOctober2008-January2009fivetest

sessionswerecarriedoutattheATPtestsiteinPapenburg

(Germany)andonthetesttrackinSintOedenrode(the

Netherlands).Inallcases,thelorryusedwasequippedwith

thefullrangeofmeasuringinstrumentation.

ToestablishtheoperationoftheselectedAPS(excluding

BBFB),testmanoeuvreswereperformedwithaloaded

articulatedlorryundercontrolledconditions[6,7].Foreach

ofthefourtypesofAPS,specifictestswereconductedto

establishthesystem’soperation.

TheexperimentsusedweretailoredspecificallytotheAPS

tested:

• ROC&DC:stationarycircletest,spiraltest,braking

inthebend,lanechanging,steppedsteeringmove-

ments,roundaboutapproach;

• ACC:approachingmovingprecedingvehicle;

• FCW:approachingmovingprecedingvehicle,

approachingstationaryvehicle;

• LDW:crossinglanelines;

Thevarioussystemsandtheirresultsarediscussedbelow.

ROC&DC

ROCisasystemmountedonatrailer;DCisasystem

mountedonthetractorunit.Bothsystemsrespondto

lateralaccelerationandintervenebybrakingoneormore

wheels.

Inthisway,thesystemsattempttocorrecthazardousdyna-

micbehavioursuchas(thelikelihoodof)thevehiclerolling

orslipping.

ThefunctionalityofROC&DCwasdeterminedbycon-

ductingmeasurementswiththetestvehicle.Intherefe-

rencesituationthesystemwasnotoperational.Duringthe

relevantmeasurement,thesystemwasagainoperational.

Topreventthevehiclefromrollingduringthereferencetest,

thetrailerwasequippedwithlateralsupportsofthetype

showninFigure6.

Asanexampleofatest,acircletestisshowninwhich

thelorryisdrivenatanincreasingspeedinacirclewitha

constantradius.TheactualresultsareshowninFigure7

andfigure8.

Thestationarycircletestwasperformedbyslowlyincrea-

singthespeedwhiledrivinginacirclewitharadiusof43

metres.Thetestwasperformeduntilthespeedatwhich

theDC/ROCactivesystemintervenedwasapproachedor

inthecasewithoutactiveAPS,therolloverlimit(pointat

whichvehiclestartstoroll).Showninfigures7and8are

themostimportantvariables,thedrivingspeedvxandthe

lateralaccelerationayforthevariousconfigurations.

Figure7showsclearlytherelationshipbetweendriving

speedandlateralacceleration.Tomaintaintheintended

circlepath,lateralaccelerationmustincreaseasspeed

increases.

3. Study of the functional effectiveness of the systems examined

Figure 6: Example of test vehicle - Source: TNO

Final report Accident prevention systems for lorries�8

Theactivesysteminterveneswhentherolloverriskbecomes

toogreat.InFigure7thisinterventionisclearlyevident

forallsignals.IntheFigures7and8weseeatthispoint

thatthelateralaccelerationsuddenlyreducesanddriving

speeddecreasessimultaneously.Atthemomentofsystem

intervention,whichthedriverfeels,thedriverrespondsby

releasingtheacceleratoranddrivingoutofthecircle.

DCintervenedatalateralaccelerationofroughly3m/s2

andROCatalateralaccelerationofroughly3.5m/s2.

ForthetestvehiclewithoutROC&DC,thespeedwas

increaseduntilslippingoccurredatalateralaccelerationof

roughly4.7m/s2.

Itisevidentfromthetestsonthecircuittrackthatboth

thesystemstestedfunctioneffectivelyintermsofautono-

mouslyinterveningandpreventinghazardoussituations

suchasrollingorslipping.Inampletimebeforeahazardous

situationoccurs,thesystemsinterveneinacorrectmanner.

3. Study of the functional effectiveness of the systems examined

Figure 7: Lateral acceleration in circle test for each type of system

Figure 8: Driving speed in circle test for each type of system

Geen AOS

Circle test

No APS

Measuring time [%]

Measuring time [%]

Circle test

No APS

Final report Accident prevention systems for lorries �9

ACC

Inthefieldoperationalteststhedriverscanadjustthe

settingoftheACC.Inthetesttracktestingthesystem’s

standardsettingwasused(DAF).Thedistanceatwhichthe

ACCintervenesaverages100metresandisnotcorrelated

withthedifferenceinspeed.Neitheristhedistanceat

minimumTTCcorrelatedwiththeapproachspeedand

variesfromapprox.23metrestoapprox.65metres.

Theapproachtest,wherebythevehiclewithactivatedACC

approachesaprecedingvehicle,isthemostappropriate

testforanACCsystem.Theapproachoccursonastraight

road;ofthetwovehiclestheprecedingvehicleisdriving

moreslowly.ShowninFigure9isanexampleofoneofthe

tests.Shownherearethecourseofthedrivingspeed,the

distancetothevehicleinfrontandthelongitudinalaccele-

ration(ax)asafunctionofthetime.

ShownintheupperplotarethepresetACCspeed(vxset

point),thelorry’sspeedandthespeedofthevehicleinfront

(acar).Attime7sthevehicleinfrontisseenbytheACC

systemandthespeedofthecarandthelorriesdistance

fromitaremeasured.

3. Study of the functional effectiveness of the systems examined

Figure 9: ACC’s reaction to approaching the vehicle in front

lorrycar

set point

Dis

tanc

e [m

]

Final report Accident prevention systems for lorries�0

Almostimmediatelyfollowingthedetectionofthecar,the

lorryissubjecttoautomaticbraking;aminimumdistance

ofapprox.17metrestothecarismaintained.Temporarily,

thelorry’sdrivingspeedfallsbelowthatofthevehiclein

frontinordertoallowtheinterveningdistancetoincrease.

Inapprox.200metresofroaddriven,theACCachievedthe

speedreductionthatwascoupledwithamaximumbraking

delayofalmost2m/s2.

ShowninFigure10areseveralkeyvariablesintheapproach

testmeasuredatvariousspeeddifferencesbetweenthetwo

vehicles,namely:

• DistanceinterventionACC-distancetothecarinfront

atthemomentthattheACCsystemintervenes;

• MFDD-MeanFullyDevelopedDeceleration:the

lorry’saveragebrakingdelay;

• MinTTC-minimumTimeToCollision;

• Distance@minTTC-distancebetweenthetwo

vehiclesatminimumTimetoCollision.

OftheabovekeyvariablesonlytheminimumTTCand

averagebrakingdelayMFDDdependonthedifferencein

startingspeedsofthetwovehicles(orrathertheapproach

3. Study of the functional effectiveness of the systems examined

Figure 10: Measured functionality of ACC on approaching the vehicle in front

Detection

Inte

rven

tion

dist

ance

AC

C [

m]

Min

imum

TTC

[s]

Dis

tanc

e @

min

imun

TTC

[m

]Distance at minimum TTC

Speed difference [km/h]Speed difference [km/h]

Intensity of braking action

Final report Accident prevention systems for lorries ��

speedoftheACCvehicletothevehicleinfront).The

minimumTTCvariesfrom25stoapprox.5satthehighest

approachspeed.Theaveragebrakingdelayincreasesuntil

approx.1.5m/s2atincreasingapproachspeed.

AminimumTTCof5sormoreisrealisedbytheACC

system.Thisisacomfortabletimesinceadriver’sreaction

timeisapprox.1secondand,moreover,thedriverhasbeen

alertedbytheACCsystem’sbrakingintervention.Assuch,

itcanbeconcludedthatundertheconditionstested(vehicle

infrontdrivesatconstantspeedandfasterthan25km/h)a

safesituationcanbeachievedwiththeACCsystem.

TheACCsystemcannotberegardedasaForwardCollision

WarningSystem.Thisisbecauseitcanbedisengagedby

thedriver.Moreover,themaximumbrakingdelaypossible

islimitedto2.5m/s2andtheprecedingvehicle’sminimum

speedmustbegreaterthan25km/hforthesystemto

intervene.Stationaryandslowlymovingobjectsarefiltered

outbytheradarsystem.

IftheACCsystemisnotcapableofrealisingasafedistance

byemployingthemaximumbrakingdelay(2.5m/s2),an

alarmisgiven.Inthiscasethedrivershouldperforma

brakinginterventioninordertoavoidacollision.

ItisevidentfromtheteststhatACCfunctionseffectively.

FCW/HMW system

FCWissuesawarningwhentheheadwaytime(TimeTo

Collision/(TTC)becomestooshort.TheTTCisdefinedas

thedistancetothevehicleinfrontdividedbythedifference

inspeed.Thestandardsettingisawarningofatleast2.7

seconds(earlierifpossible).

HMWissuesawarningassoonasthevehicleapproaches

toocloselythevehicleinfront.

ThewarningsissuedbyHMWcomeinfoursteps:

• Exceeding2.5seconds grey

• Between1.1and2.5seconds green

• Between0.7and1.1seconds orange

• Lessthan0.7seconds red

Thesystemworksatanyvehiclespeed.Thesettingsshown

abovewereusedinboththetesttracktestsandthefield

operationaltest.

InordertotesttheFCW/HMWsystemthelorrywas

driventowardsastationaryvehicleandaprecedingvehicle

movingmoreslowlythanthelorry.TheFCW/HMWcannot

interveneindependently;itwarnsthedriveroftheneedto

reducevehiclespeed.Inthetests,thedriverbroughtthe

vehicle,immediatelyfollowingawarning,toahaltinthe

availabledistance.

FromtheresultsitisevidentthattheFCWissuesanalarm

ataTTCbetween2.5and4.2seconds,dependingonthe

approachspeed(10to80km/hr)andthedifferencein

speedbetweenthetwovehicles.Thedistancetotheprece-

dingvehicleisthenbetween20and70mdependingonthe

differenceinspeed.

3. Study of the functional effectiveness of the systems examined

Final report Accident prevention systems for lorries��

ShowninFigure11areseveralkeyvariablesintheapproach

testwiththeFCW/HMWsystemproducedbyClifford

Electronics/Mobileye:

• Detectiondistance-distancetocaratthefirstmoment

thattheFCW/HMWsystemhasdetectedthecar;

• TTCFCW-TimetoCollisionatthemomentthatan

audioalarmisgiven;

• MFDD-MeanFullyDevelopedDeceleration,average

brakingdelay;

• Distance@TTCFCW-distancetocaratTimeTo

Collision.

Fromthefigures,itisevidentthatthesystemdetectsthe

vehicleinfrontinmosttestsatmorethan100metres.In

onlythreecaseswasthedetectiondistanceshorter,namely

approx.70metres.Thedriverreceivedwarning,excepton

twooccasions,twosecondsbeforeapossiblecollisionviaan

audioalarm(TTCFCW).

Duringthewarning,thedistancetothevehicleinfrontwas

approx.10metrestoapprox.70metresatanapproach

speedof10km/hto80km/hrespectively.

3. Study of the functional effectiveness of the systems examined

Figure 11: Measured warning times, distances, etc. issued by FCW/HMW upon approaching vehicle in front

Speed difference [km/h]

Distance at FCW warning

Detection

Dis

tanc

e @

min

imun

TTC

[m

]

Speed difference [km/h]

TTC at FCW warning

Det

ectio

n di

stan

ce [

m]

Intensity of braking action

Final report Accident prevention systems for lorries �3

Thetestdriverwasabletoavoidacollisioninalltests.The

brakingdelaysthisrequired(seeMFDDinFigure11)indi-

catethatatthegreaterspeeddifferencesitwasnecessary

tobrakefirmlytoveryharshly(maximumbrakingdelay5

m/s2=emergencystop).TheminimumTimetoCollision

variesfrom1.2toapprox.3secondsandtheassociated

minimumdistancesareapprox.3to12metres.

Innotestdidthelorrycomeintocontactwiththepreceding

vehicle.Thedriver’sreactiontimeaveraged0.35seconds,

whichcanbeconsideredveryquick;thetestdriverwasable

toreactsoquicklybecausehe/sheknewthatawarning

wouldbegiven.Inaccidentreconstructionsareactiontime

of1secondisassumed.Thus,atnormalreactiontimesand

withconstantbrakingdelays,thelorrywouldinallproba-

bilityhavecomeintocontactwiththeprecedingvehicle.In

thatcase,theimpactofthecollisionwouldstillhavebeen

reducedbythereducedcollisionspeed;andtheseverityof

theconsequenceswouldalsohavebeenreduced.

ItisevidentfromtheteststhatFCW/HMWfunctions

effectively.

3. Study of the functional effectiveness of the systems examined

Figure 12: Measured warning times and line crossings for LDWA

Max

imum

cro

ssin

g [m

]

50 km/h80 km/h

50 km/h80 km/h

Steering wheel angle (deg)

Final report Accident prevention systems for lorries�4

LDWA system

TheretrofitLDWAsystemproducedbyMobileyehasthe

followingcharacteristicsettings:

• Becomesactiveatspeedsinexcessof55km/hr,and

becomesinactiveoncemoreifthespeeddropsbelow

50km/hr.

• WarningforaTimetoLineCrossing(TTLC)of0.5

seconds.

• Afterawarning,thenextwarningwillbegivenonly

ifthevehiclehassincereturnedtoitslaneandthe

distancetotheroadlineismorethan0,3m(toavoid

overuseofthealarm).

• Nowarningifindicators/alarmlightsareoperational.

Thecrossingofthelanelineswastestedwithsmallsteering

movements.

Inordertodeterminethespeeddependency,themeasu-

rementswereperformedattwospeeds:50km/hrand80

km/hr.

Figure12illustratesthetimebetweenwarningandline

crossing(tcross-twarn).Thelowerpartofthegraphshows

themaximumcrossingsdependingonthedrivingspeedand

steeringwheelangle.

Thewarningtime(timebetweenLDWAalarmandactual

crossing)amountedtoapprox.0.2to0.6secondswithan

averageof0.35seconds.Inmanycasesthewarningtime

isshorterthanthe0.5sstatedinthesystemspecifications.

Inmostcases,thecrossingwaslimitedtoonetyrecrossing

theline.

ItisevidentfromtheteststhatisLDWAfunctionally

effective.

3.� Loan test

AsthedataregistrationsystemsusedinFOTprovideonly

limitedinsightintotheeffectsofDirectionalControl(DC)

andRolloverControl(ROC),theuseprofileofalorrywas

establishedinrelationtotherolloverriskoverafive-week

period[6,8]usingavehicleequippedwiththefullrangeof

measuringinstrumentation.Duringthistest,knownasthe

loantest,varioushaulagefirmsmadeatotalof107trips

withalorrycarryingTNOinstrumentation.Participating

driverswerechosenatrandomfromamongtheemployees

ofthehauliers.TheloantestwaslimitedtotheDC/ROC

system.

AtthestartofeachtripduringtheloantesttheRoll-over

PropensityAssessmentSystem(RPAS)[1]estimationalgo-

rithmwasusedtodeterminethecriticallateralacceleration

(=rolloverlimit).Therolloverlimitisthelateralacceleration

atwhichthevehiclebeginstoroll.Thisisdependenton,

amongotherthings,theload,whichcanvarywitheach

trip.

Usingtheestimatedrolloverlimit,foreveryminutethat

thevehicledrovefasterthan15km/h,themaximumroll-

overriskthatoccurredwascalculatedandlogged(inthat

minute).Therolloverriskisdefinedasthemeasuredlateral

accelerationdividedbytherolloverlimit.

3. Study of the functional effectiveness of the systems examined

Final report Accident prevention systems for lorries �5

ThehistograminFigure13presentsasummaryofthe

resultsfortheentiretest.Itcanclearlybeseenthattheroll-

overriskmoreoftenassumesrelevantvaluesforaloaded

vehicle(theorangebars).Thenumbersabovethevertical

barsinthegraphshowthenumbersofminutesforan

empty(i.e.lessthanapprox.20%loaded,blue)andladen

(orange)vehiclerespectively.

Intotaltheriskvalueof45%wasexceededin24minu-

tes(thus24times)whilethelorrydrovefor6,849minu-

tes(6,849registeredevents)(0.35%).Whilethisseems

sporadic,itisbasicallyonceadayonaverage.Inincidental

casesthiswillleadtoaninterventionbyDCat55%rollover

risk.AninterventionbyROCislesscommonbecausethat

systemintervenesonlyatarolloverriskof70%.

3. Study of the functional effectiveness of the systems examined

Figure 13: Distribution of measured rollover risks

Distribution of rollover risk at driving speed exceeding 15 km/h

EmptyLaden

Rollover risk [%]

Num

ber

of r

egis

trat

ions

[m

inut

es]

Final report Accident prevention systems for lorries�6

TheinfluenceofloadingisshowninFigure14.Foroneof

themeasuringdays,therolloverriskmeasuredisshownfor

variousloadlevelspertrip.Theloadlevelsareexpressedas

percentagesandshownbydifferentcolours.Thehighest

rolloverriskoccursonthisparticulardaywithaloadexcee-

ding80%(black).Afteroffloadingtheloadto50%(blue)

almostthesamemaximumrolloverriskoccurs.Itseemsthat

thedriverseeksthesamelevelofrolloverriskeachtime.

Theanalysisshowsthefollowing:

• InterventionsbyDCarerare;

• TheDCdiscussedherewasinstalledonthetractorunit

andintervenesearlierthanROCinstalledonthetrailer

unit;

• Therolloverriskduringnormaluseisconsiderableless

thantheROCtriggerlevel.

Onlyinthesituationwiththehighestrecordedrolloverrisk

didtheDCsystemintervene.TherolloverlimitforROC

interventions(=70%)wasnotexceeded,andcorrespon-

dinglynoROCinterventionswereregisteredduringthe

loantest.

3. Study of the functional effectiveness of the systems examined

Figure 14: Measured rollover risk depending on the load (one measuring day)

Rol

love

r ris

k [%

]

Time [hours]

Final report Accident prevention systems for lorries �7

Theresultsofthetestsuggestthatdrivershaveagood

senseoftherolloverriskatvariousloadlevels.

FurtheranalysisoftheDCinterventionrevealsthatahigh

rolloverriskoccursprimarilyonmotorwaysliproads(both

entrancesandexits)andonclover-leafintersections.This

ismostlyinlongbendsattheendofthebend,wherethe

driverincreasesspeedinanticipationofthestraightroad

sectionthatfollows.

Ahighrolloverriskusuallyoccursseveraltimeswithinatrip

andoftenduringmultipletripsonthesameday,irrespective

oftheload.

Figure15showsthelocationandtheroutedrivenwhere

theDCsystemintervened.Theroutetravelledisshownby

thecyanline,startingontheleft-handsideofthefigure.

Thevehicledroveontheright-handsideoftheroad.

TherolloverriskandothervariablesareshowninFigure

16.Therolloverriskisshowninthebottomtwofiguresby

meansofthecoloursgreen-yellow-red-blue(fromlow

tohighrisk).Duringtheblueparts,DCintervened.

The‘s’indicatesthestartingpointofthemeasurement.

Thefigurealsoshowsthemeasuredvehiclespeed,steering

wheelangle,lateralaccelerationandlateralandlongitudinal

positionsexpressedinthexandypositions.

3. Study of the functional effectiveness of the systems examined

Figure 15: Route driven - Source: TNO

Final report Accident prevention systems for lorries�8

Withregardtotheoccurrenceofelevatedrolloverrisk,the

followingisconcluded:

• Theinfrastructureisanimportantfactor.Situations

thatappearfrequentlyinthelistofelevatedrollover

riskare:motorwaysliproads(entrancesandexits),in

clover-leafintersectionsandconnectingroadswith

straightsectionsandbends.Thehighestrolloverrisk

oftenoccursattheendofthebendwherethedriver

increasesspeedinanticipationofthestraightroad

sectionthatfollows.

• Theloadlevelisanimportantfactor.Emptylorries

havelesschanceofrollingthan(heavily)loadenlorries.

• Inallcasesthedrivermaintainedasufficientmargin.

3. Study of the functional effectiveness of the systems examined

Figure 16: Rollover risk measured during trips by a bend (with DC intervention)

60.6

605 LF 20080916 060000 15. min delay = -1.0 [m/s2], DC= 1

Time [s]

Spee

d [k

m/h

]R

ollo

ver

risk

[%]

Del

ay [m

/2s]

G

ust

[m/3

s]

Final report Accident prevention systems for lorries �9

4.� Field Operational Test general

IntheEUprojectFESTA[9,1]aFOTisdefinedas:

A study undertaken to evaluate a function, or functions,

under normal operating conditions in environments

typically encountered by the host vehicle(s) using quasi-

experimental methods.

Theplanning,performingandanalysisinvolvedinaFOT

carriedoutunderidealcircumstancesareshownbythe

FESTA‘V’,seeFigure17.

Brieflystated,thismethodologyinvolvesfirststudyingfunc-

tionality,inthiscasetheAPS.Thetrickistosubsequently

translatetheresearchquestionsintotestablehypotheses.

Onceitisknownwhatmustbemeasured,(andhowoften/

accurately),measurementsandsensorscanbechosenand

thedataregistrationdesigned.

Subsequently,theearlierhypothesiscanbeverifiedornot

usingtheanalysisofthedatabaseofmeasurements.Asa

result,policystatementscanbemade.

4. Field Operational Test

Figure 17: FESTA method

Final report Accident prevention systems for lorries30

Inpractice,compromisessometimeshavetobemadetobe

abletorealiseaworkablefieldoperationaltest.Inthecase

ofAPSthemainchallengewastoequipasmanylorriesas

possiblewithAPSanddataregistrationsystems,andthento

ensurethatthedataregistrationfunctioned.

Thatresultedin:

• Anumberofpotentiallydisruptiveinfluenceslikethe

weather,trafficjamsorroadworksnotbeingableto

bedirectlymeasuredbutonlyindirectlyderivedand

added;

• Measurementsbasedoneventsratherthancontinuity;

• Theuseoftwodifferentdataregistrationsystems;

• Aninabilitytoselectparticipantsrandomly;

• Aninabilitytorandomlyallocatesystemstopartici-

pants;

• Thedriversintwosub-groupsinsubprojectsbeingable

toswitchofftheAPSwithoutthepossibilityofmonito-

ringthat;

• Alimitedtimetocheckthequalityof,andsubsequent-

lyanalyse,thedata.

4. Field Operational Test

Figure 18: The effect of APS on the indicators

Whole APS group

Traffic flow Safety

Fueluse

Averagespeed

Speedvariation

Use ofcruisecontrol

Headwaytime

Number of times

hard braking

Number of vehicles per

minute

Frequencyof short

headway time

Number of accidents

Accidentseverity

Speed difference at accident

Speedat

collision

Frequencyof lane

breaching

Distanceto lanemarking

Final report Accident prevention systems for lorries 3�

Todeterminetheeffectsontrafficsafety,indicatorswere

identifiedthathavearelationshipwithtrafficsafetyand

flow.

Byvirtueofitsoperation,eachoftheseparateAPShasan

assumedeffectontheindicatorsofbothdomainsasvisua-

lisedinFigure18.Itshouldbestatedthatotherfactorsalso

influencetheseindicators.Howsuchdisruptivevariables

arehandledisexplainedingreaterdetailinSection5.3The

Relationship between APS and safety.

ThepossibleeffectsofAPSontheindicatorsultimately

translatedinto30testablehypotheses.Anumberof

hypothesesweretestedforalltypesofAPSandanum-

berofhypothesesweretestedforeachindividualAPS.All

hypotheses(includingthosethatcouldnotbetested)are

presentedinAppendix2.

Theexperimentalsituation(thevehicleswithactiveAPS)

wascomparedwiththereferencesituation(thereference

vehicleswithwhatisknownasa‘silentAPS’).Intherefe-

rencegroup,thedriverswerenottoldbutweremeasured.

TheanalysiswasperformedonlyfortheDutchmotorway

system.

Forthepurposesoftestingthehypotheses,thedatawas

dividedinto:

• TheAPSgroups;

• Light(aftersunrise-aftersunset,basedondateand

time);

• Speedlimit(80-100-120km/hr).

4.� Selection and distribution of participants

in field operational test

Inall,123haulierswerefoundtoparticipateinthefield

operationaltest(FOT).Theirlorries,includingtheirtechnical

specifications,wereincludedinwhatisknownasthezero

database.FourOEMs(DAF,VOLVO,MAN,Scania)were

foundwillingtosharedetailsofsomeoftheproduction

withtheprojectteamtoenablethejointassessmentof

whichorderswouldbeeligibleforbuildinginACCorLDWA

(factory-fitted).

Basedonthespecificationsandthepossibilities,thenext

stepwastoexaminewhichlorriesweremostsuitedto

whichgroup,howthegroupscouldremainascomparable

aspossibleandthe‘bias’resultingfromtheselectioncould

beminimised.

4. Field Operational Test

Final report Accident prevention systems for lorries3�

Inaddition,thefollowingweretakenintoconsideration:

• Nationalversusregionaltransport;

• Haulierswithlarge(>50lorries)versussmallfleet;

• Averagetriplengthinkilometres;

• Useoflorriesduringdayoratnight;

• Typeoftransport(forexample,generalcargoor

hazardousmaterials);

• Ageoflorry(yearofmanufacture2001orlater).

Incontrasttoearlierrecommendations,severaltypesof

lorrieswerechosenratherthanonetype.Withjustone

type,thefieldoperationaltestwouldnothavebeenlarge

enoughtoenablestatisticallysoundjudgementsorthe

numberoftypesofsystemintheFOTwouldhavehadto

havebeenlimited.

Lorrieswithadateofmanufacturepriorto2001were

excludedfromtheselectionbecausetheriskofdrop-out/

saleduringtheprojectcouldbeconsideredrealistic.Forthe

detailedelaborationoftheselectionmethod,readersare

referredto[10].

ThesummarisedresultoftheselectionispresentedinChart

1basedontheactivitiesofthehaulierandthetypesof

lorry.Thetotalismorethan100%becausecompanieswere

abletogiveseveralanswers.

ThetypeoflorryisdescribedinChart2.

InordertomakethetestingofBBFBfeasible,itwasdecided

toselectcompaniesalreadyusingtheCarrierWebonboard

computer.

4. Field Operational Test

Chart 1: Activities of participating companies

Chart 2: Lorry type distribution

% companies

General cargo 60

Liquid bulk 25

Solid bulk 18

Hazardous cargo 28

Containers 20

Exceptional transport 10

Other 8

Combination Total %

Motorisedvehicle 332 14%

Motorisedvehicle-container

14 1%

Unknown 119 5%

Articulatedlorry 1.674 70%

Articulatedcontainerchassislorry

66 3%

Articulatedcontainerlorry

197 8%

Sum total �.40� �00%

Final report Accident prevention systems for lorries 33

Figure19showsthedistributionofthesystemsacross

varioussubprojects(SPs)andthenumbersofvehiclesper

SPinwhichanAPSwasbuiltin.Intotal2,402vehicleswere

involvedintheprojectdistributedacrossfoursubprojects.

Thefeaturesofthesubprojects(SPs)wereasfollows:

SubProject1consistedoflorriessomeofwhichwereequip-

pedwithAPSretrofitsystems.Thedataregistrationwas

carriedoutusingamodified‘ClearBox’systemproducedby

CliffordElectronics/OctoTelematics.Thedataregistration

systemalsomeasuredanumberofdataitemsfromtheAPS

concerned(Mobileye).Thereferencegrouphada‘silent’

Mobileyeonboard.Asaresult,measurementscouldbe

takenbutthedriverreceivednoalerts.Thedriverwasnot

abletodisengagethesystem.

SubProject2consistedoflorriessomeofwhichwereequip-

pedwithaMobileye(FCW/HMWandLDWA),andsome

withonlyaBBFB.Thedataregistrationsystemwasprovided

byCarrierWeb.ThedriverwasabletodisengagetheMobil-

eyewithoutthisbeingregistered.

4. Field Operational Test

Figure 19: Vehicle distribution across sub-projects

SP2 Driver project: 656

Reference 234 Reference86

Reference 411

SP4: Test track: various systems: 1

Final report Accident prevention systems for lorries34

SubProject3consistedoflorrieswithAPS,almostallof

whichwerefactory-fitted.Thedataregistrationwascarried

outusingamodified‘ClearBox’systemproducedbyClif-

fordElectronics/OctoTelematicsanda‘silent’Mobileye.

ThedriverwasabletodisengagetheACCwithoutthis

beingregistered.

SubProject4consistedofthelorrythatwasusedforthetest

trackexperiments.

Intotal2,402lorrieswerefittedwithequipment.However,

thenumberoflorriesforwhichmeasurementresultswere

savedislowerthanthisnumber(2,086lorries).Thisisbe-

causeatthestartoftheprojectnotalllorrieswereequipped

withAPS,whilelaterintheprojectlorriesdroppedoutdue

totheirsaleorlackofuse.Thiswasattributabletoarange

offactors,includingtheeconomiccrisis.

4.3 Data registration InSubProject1andSubProject3dataregistrationtookplace

usingregistrationunitsproducedbyCliffordElectronics/

MobileyeandOctoTelematics.Theseunitswerebasedon

the‘ClearBox’conceptdevelopedbyCliffordElectronics[2]

andOctoTelematicsandaMobileye.

Foradetailedanalysisandauditofthisdataregistrationand

thedatashownbelowthereaderisreferredto[21].

WiththeaidofaGPRSconnection,aGPSreceiver,anacce-

lerationsensorandaCANbuslinkwiththeAPS(Mobileye:

LDWA,FCW/HMW)threetypesofdatawerecollected(see

[2,3]fordetailedspecifications.

Standarddata:

• Startoflocation(GPScoordinates);

• Endoflocation(GPScoordinates);

• Everytwokilometres:

- Date/time;

- GPScoordinates/GPSspeed;

- Momentaryheadwaytime;

• Crashtriggerdata:

- Iftheaccelerationsensormeasurestoohigha

value(triggerevent,configurable);

- Speedandaccelerationbeforeandafterthe

triggermoment;

• Diagnosticdata.

APSeventdata:

• EventdataAPS:

- IftheAPSmeasuresanevent(triggerevent,

configurable);

- Typeofevent,date/time,GPScoordinates/GPS

speed.

APSdetaileddata:

• Triggeredbyanevent;

• Detailedsnapshotlastingapprox.6secondsbeforethe

eventuntil4secondsaftertheeventof:

- GPScoordinates/GPSspeed;

- Accelerationsasmeasuredbythesensor;

- Mobileyedata.

ThesedatawereenhancedbyOctoTelematicswithGIS

data(convertedtogeo-codesforroads),filteredwhere

necessary,andclusteredtoformanumberofdatafiles.The

acquisitionsystemforSP2differedfromalltheothersbe-

causeitwasgeneratedusingthefleetmanagementsystem

producedbyCarrierWeb.Inthiscase,‘events’istakento

meanthemeasuredsignalsissuedbytheaccidentpreven-

tionsystems.

4. Field Operational Test

Final report Accident prevention systems for lorries 35

Thefrequencywithwhichthedataweresavedwasonce

everytwominutes.Nocurrentvaluesweresavedbutrather

indicators,whichwerecalculatedimmediately,concerning

theelapsedperiodof2minutes,forexampletheaverage

speedandthemaximumacceleration/deceleration.

Therawdatafromthedataregistrationwerequalitycon-

trolledpriortoprocessingandfilteredagain,ifnecessary.

Duringsub-analysessubsetswereenhancedwithvariables

ofimportancetotheanalysis,suchasthefilesofactualdata

basedonthemeasuredGPSpositions,roadtype,numberof

lanes,applicablespeedlimits,etc.

Owingtotheconversionandtheadditionofindexation

data,thefilesthatwereanalysedbecamelargerthanthe

originaldatafiles.

Chart3showsthequantityofrawdatacollectedin

SubProject1andSubProject3.Thetotalismorethan170

GigaBytes.

Chart4showsthenumberofkilometresdriventhatwas

loggedpermonthinSubProject1andSubProject3.The

numberoflorrieswasdeterminedeachmonthbyarangeof

factors,includingtheavailabilityofunitsandtherepairand

modificationofAPS.

Chart5showsthequantityofrawdatacollectedinSubPro-

ject2.Thetotalismorethan14GigaBytes.

4. Field Operational Test

Chart 3: Amount of data collected from sub-projects 1 and 3

Chart 4: Kilometres driven and measured in sub-projects 1 and 3

Data file Data Space (Mb)

TRIP_SUMMARY 71

TRIP_DETAIL 49.372

APS_SUMMARY 19.678

APS_DETAIL 103.072

CRASH_SUMMARY 11

CRASH_DETAIL 361

Total �7�.860

Year Month Total km driven Total journeys

Average kilometres per day Number of lorries

2008 10 8.145.428 248.417 345 1.043

2008 11 8.173.006 248.136 333 1.223

2008 12 8.818.063 254.757 333 1.304

2009 1 9.259.496 264.454 328 1.350

2009 2 9.203.939 276.281 322 1.469

2009 3 10.800.269 330.630 323 1.493

2009 4 10.218.884 311.555 326 1.498

2009 5 9.033.672 278.108 310 1.547

Total 73.65�.757 �.���.338

Final report Accident prevention systems for lorries36

Chart6showsthenumberofkilometresdrivenandmeasu-

redinSubProject2.

Thenumberoflorrieswasdeterminedeachmonthbya

rangeoffactors,includingtheavailabilityofunitsdelivered

factory-fittedandtherepairandmodificationofAPSand

dataregistrationunits.

4.4 Analysis of measurements

Owingtothelengthymeasuringperiod,particularlyinSP1

andSP3,allsortsofweatherconditionswereencountered,

fromextremecoldinthewinter(to-20°C)toheatinthe

spring(30°C),dryweather,wetweatherandsnow.Data

thatwasinfluencedbyextremeweather,suchasthesnow

inJanuary2009thatwasextremebyDutchstandards,have

notbeenincludedintheanalysis.

ThehypothesespresentedinAppendix2weretestedinthe

dataanalysis.Thisinvolvedtheuseofvarianceanalysis.The

analysiswasperformedondatacollectedonDutchmotor-

waysandforspeedsinexcessof55km/hr.

Theindependentvariableswere:

• APS(withtheconditionsLDWA,FCW/HMWand

referenceservingasexamplesinSP1).

• Thespeedlimit,with120,100andoccasionally

80km/haspossiblevalues.Thisvariablewas

correlatedwiththelocationwherethelorrydrove.

Thelimitof100km/hisfoundtypicallynearurban

areasandaspeedlimitof80km/happliedatacouple

ofspecificlocations.

• Half-day,withdayandnightaspossiblevalues.This

variableincludestheeffectsofbothlightconditions

andweightoftraffic.

OfthehypothesesinAppendix212turnedouttobesigni-

ficant,18hypotheseswerenotsignificant,and23hypothe-

sescouldnotbetestedforarangeofreasons,includingthe

lackofsufficient(correct)dataspecifictothehypothesisin

question.Themostimportantfindingsareshownbelow.

Forthedetailsoftheanalysis,thereaderisreferredto

Appendix5.

ThedivisionintogroupsanalysedandassociatedAPStypes

andvehiclecategoriesisshowninChart7.

4. Field Operational Test

Chart 5: Amount of data collected

Chart 6: Kilometres driven and measured in sub-project 2

Data file Data Space (Mb)

Haulier1_data 400

Haulier1_GPSdata 1.200

Haulier2_data 2.400

Haulier2_GPSdata 10.300

Total �4.300

Year Month Total km driven

Number of lorries

Haulier �

3 101.459 51

4 227.330 51

5 253.975 86

Subtotal 58�.764

Haulier �

2009 2 50.082 71

2009 3 698.452 405

2009 4 800.042 455

2009 5 920.263 453

Subtotal �.468.839

Total 3.05�.603

Final report Accident prevention systems for lorries 37

SubProject1andSubProject3aresimilarintermsofdata

registration,SP2differsfromthem.Inordertoachieve

comparablegroups,theanalysesinthesetwogroupswere

performedseparately.

Twohaulierswithdifferentbusinessmodelscooperatedin

SP2(owndriversversusleaseoflorries).Thesearerefer-

redtoasHaulier1(Tr1)andHaulier2(Tr2).Sincethisfact

couldbeinfluential,ithasbeenincludedintheanalysis.

ThenumberoflorriesinChart7islowerthanthetotal

numberoflorriesfollowed.Asignificantcauseofthisisthe

removalfromtheanalysisofanumberoftypesoflorries

necessitatedbytherebeingtoofewofthemtoperforma

goodanalysis(forexample,some4-axislorries).

Inaddition,itwasfoundthatsomeofthelorrieshaddriven

almostexclusivelyoutsidetheNetherlands,asaresultof

whichtheyprovidednodata.

Group � (Octo data registration system)

ThesubgroupsSubProject1andSubProject3(LDWA,FCW/

HMW,DC,ACC,Octodataregistration)wereanalysed

together.

• Variouspositive,statisticallysignificanteffectswere

foundforACC:higheraverageheadwaytimehigher,

%headwaytimes<1slower,fewerFCW/HMW

alertsandfewerLDWAalerts.However,whetherthe

ACCwasswitchedonoroffcouldnotbemeasuredor

indeedwhatthesettingwas.Thereforeitcannotbe

demonstratedwhethertheeffectisduetoACCuseor

ownership.Thedriversurveysrevealgreatsatisfaction

withACC,whichcouldindicateahighlevelofACCuse.

• AnLDWAreducesthenumberofwarningsperhour.

Thus,anLDWAleadstofewerunintentionalline

crossingsorbetteruseoftheindicators.Thegroup

withanLDWAfittedpost-factoryshowsadecreaseof

30%,the‘factory-fitted’groupupto60%.The

percentageofshorterheadwaytimes(<1s)increases,

however,asaconsequenceofanLDWA.

• FCW/HMWhasnomeasurableeffectinthepercenta-

geofshorterheadwaytimes(<1s).Asubsequent

analysisindicatedthatintheaverageheadwaytimea

measurablepositiveeffectwasindeedobserved

(0.14s).

4. Field Operational Test

Chart 7: Classification of APS groups

SP� RetrofitSP3 OEM SP� Drivers

SP3a: Bulk SP3b: OEM Tr� Tr�

APS LDWAFCW/HMWReference

DCLDWA(retro)

Reference

BBFBReferentie

BBFBLDWA+FCW/

HMWReference

Vehicles ArticulatedlorryMotorisedvehicle

Articulatedcontainer

chassislorryArticulatedlorry

ArticulatedlorryArticulated

containerlorry

Articulatedlorry(4x2en6x2)

Articulatedlorry(4x2)

Number 1.230 143 194 78 487

Data Octo CarrierWeb

Final report Accident prevention systems for lorries38

Group � (CarrierWeb data registration system)

ThesecondanalysiswasperformedonthedataforSub-

Project2(BBFB,LDWA+FCW/HMW,CarrierWebdata

registration).InSubProject2noACCwasusedbutitwas

knownwhetherthecruisecontrolwasonoroff.Thisfact

hasbeenincludedintheanalysis.Inaddition,inthisgroup

LDWAandFCW/HMWwereusedonlyincombinationwith

oneanother.

ForbothhauliersalimitedandcontraryeffectoftheBBFB

wasevidentontheaveragespeed.Thefirsthaulier(own

drivers)demonstrateddesirablebehaviour:24%lessspeed

variation.Thesecondhaulier(leasedlorries)demonstrated

slightlyundesirablebehaviour:5%morespeedvariation.

LDWAandHMW/FCWappeartohavea(small)effecton

averagespeed.Averagespeedwas0.4km/hlowercompa-

redtothereferencegroup.

Theuseofacruisecontrolhadonlyasmallmeasurable

effect:foranengagedcruisecontroltherewasamarginally

higheraveragespeed(2.2to2.7km/hr)andaswouldbe

expectedwithfewervariationsinspeed.

TheBBFBwasnotseentohaveanyeffectontheuseof

cruisecontrol.Ananalysiswasperformedforthenumber

oftimesharshaccelerationoccurred(>1.5m/s2)andthe

numberoftimesharshdecelerationoccurred(<-0.8m/s2).

ThemeasureddifferencesaresmallbuttheBBFBgroup

brakedharshlylessoftenthanthereferencegroupandless

oftenthanthegroupwiththeCliffordElectronics/Mobileye

system(FCW/HMWandLDWA).

4.5 Data validation

Owingtotherelativecomplexityofcollectingsomuchdata

fromthisnumberofparticipants,Ernst&Youngperformed

anauditofthedataregistrationandprocessingcarriedout

bytheClifford/Octosystem,fromlorrytorawdata[21].

Theconclusionoftheauditreadsasfollows:

The three answers prove that raw data process of collection

and export is robust and reliable. Some minor integrations,

described in detail in each section of this document, should

be performed.

Twovalidationswereperformedforsubprojects1and3,

bothattheendofthemeasuringperiod.Inthefirst[20]

theeventsinthefieldwerecountedmanuallyandcompa-

redwiththeeventsthatwereloggedinthedatabase.This

concernedavalidationofthreevehicles,allthreetracked

throughoutoneday.Whileitturnedoutthatnotallevents

hadbeenlogged,nonewdeviationswereidentified.

Thedeviationsobservedoccurredinallgroups(reference

andthetwoAPSgroups)andarenotexpectedtointroduce

anybias.

Thesecondvalidationtest[21]validatedtheprocessesof

datastorageandprocessing.Nodeviationsworthyofmen-

tionwererevealed.

4. Field Operational Test

Final report Accident prevention systems for lorries 39

5.� Literature study

Inordertobeabletoextrapolatetheresultsofthefield

operationaltesttoapredictionabouttheeffectsontraffic

safetyinlarge-scaleapplication,aliteraturestudywasfirst

carriedout.

Inmanyofthestudiesfound,noverdictsweregivenabout

theeffectsofAPSonsafety,althoughmentionwasmade,

forexample,ofachangeinheadwaytimeandtheauthor

intentionallygavenoquantitativeassessmentaboutthe

impactofthisonsafetyorthenumberofaccidents.The

generalquantitativetendencyistosuggestthatAPSshould

haveapositiveeffectontrafficsafety.

Anumberofstudiesdiscussedinthischapterdomakea

quantitativejudgement,thoughthefollowingremarksneed

tobemade:

• Thestudiesfocusgenerallyoncarsratherthanlorries.

• Oftenthecausalitybetweenthemeasuredeffectand

predictionforsafetyortrafficflowispoorornoteven

described.

• Ifpercentagesarestatedtheymustberelatedtothe

numberofaccidentstowhichtherespectivetypeof

APSrelates.Thesearenotpercentagesthatdescribean

effectonallaccidents,sotheysometimesappearlarge

whiletheyarenotintermsofthetotalnumberof

accidents.

• TheAPSsettingsareusuallynotsupplied.

• Inpredictingtheeffectsanassumptionismadeofa

penetrationlevelofsystemsof100%,soacomplete

environmentalchange.

Thismeansthatthenecessaryamountofcautionmustbe

takenwhenusingtheconclusionsofthesestudies.

Differentmethodsareusedintheliteraturetoestimatethe

effectsofAPSonsafety:

• Comparisonofthenumberofaccidentswithand

withoutAPS.

• Bydrawingonexistinguseprofilesnotinvolvingthe

useofAPS,estimatesweremadeconcerningthe

possibleeffectsoftheuseofAPS.

• BymeasuringtheeffectsofAPSonindirectvariables

(headwaytime,variationinspeed,brakingdelay,etc.),

areductioninthenumberofaccidentswasestimated.

Accordingtothestudiesconsulted,FCW/HMWsystems

canhaveapositiveeffectonsafety.Severalstudiesmake

nojudgementsconcerningthereductioninthenumberof

accidentsbutlimitthemselves,forinstance,toajudgement

aboutthereductionincriticalsituations.

Thestudiesthatdoestimatedirecteffectsontrafficsafety

generateverydiversefiguresrangingfrom10%to21%

reductioninthenumberofaccidents,largelyattributableto

thepreventionofcriticalsituationsinvolvingshortheadway

timesthatcanbeachievedusingthissystem.

Itshouldbenotedthatthe21%hasanuncertaintymargin

of24%,whichmeansthattheresultcanalsobe-3%or

45%.

5. Study of the effect on safety

Final report Accident prevention systems for lorries40

Accordingtotheliterature,theuseofanLDWAsystemcan

alsohaveapositiveeffectonsafety.Specificeffectsarea

decreaseinlinecrossings(intentionalandunintentional),an

increaseintheuseoftheindicatorandelevatedalertness.

Theassumedpotentialreductioninthenumberofaccidents

variesfrom5%(onmotorways)to13%(onsecondary

roads).

AsfarastheeffectsofACConsafetyareconcerned,the

literaturepaintsapositivepicture.Ingeneral,theuseof

ACCisresponsibleforreducingthevariationinspeedsand

longerheadwaytimesandheadwaydistances.Estimates

indicatethattheseeffectscandeliverareductioninthe

numberofaccidents(of25%onmotorwaysto49%on

secondaryroads).However,possiblenegative(indirect)

effectsarealsoreported,inparticularanincreasedriskfor

traffictravellingbehindvehicleswithACCandreduced

trafficflow.

Feedbackaboutdrivingbehaviourseemstobecapableof

havingapositiveeffectonsafety,accordingtothelitera-

ture.Anddriversevidentlyappreciatefeedback.Sometimes

theeffectsappearnottobelasting.Ifalllorrieswereequip-

pedwithaBBFBsystem,therewouldbeasignificant

eductioninthenumberofaccidentsinvolvinglorries

rangingfrom15%to38%.

NoquantitativeresultsforDCwerefoundintheliterature.

ForESC/ESP(theequivalentofDCforcars)areductionof

between17%and27%isexpectedinthenumberofacci-

dents.Researchstudiesshowthatsystemsthatmonitorthe

vehicle’sstabilityandinterveneinsituationsinwhichthere

isachanceofthevehiclerollingoverorcontrolbeinglost

haveapositiveeffect.

Thetypeofaccidentonwhichstabilitysystemscanhavea

positiveeffectdepends,ofcourse,ontheparticularsystem’s

specificfunction.Inaddition,theeffectsappeartobe

greateronawetroadsurface.Incidentally,stabilitysystems

canalsogiverisetoanunfavourablebehaviouraladaptation

duetodriversrelyingtooheavilyonthesysteminuse.

Tosummarise,theliteraturestatesthefollowing:

• FCW/HMW,LDWA,ACCandBBFBsystemscanhave

apositiveeffectonsafety;

• Researchshowsapositiveeffectofsystemsthat

monitorthevehicle’sstabilityandintervenein

situationsinwhicharolloverorlossofcontrolmay

occur.

However,thereisanabsenceofagenerallyacceptedand

usabletheoreticalframeworkthatattemptmorequantita-

tivelytolayarelationshipbetweenmeasuredbehaviourand

theeffectsonsafety.Pleaserefertothereports[4,5]forthe

literatureconsultedandforamoredetaileddescriptionof

theresultsfound.

5. Study of the effect on safety

Final report Accident prevention systems for lorries 4�

5.� SWOV analysis of accidents in the

Netherlands

TheDutchnationalroadsafetyresearchinstitute(SWOV)

undertookananalysisoftheaccidentsonDutchmotorways

forthepurposeofthisproject[26].

TheaveragenumberoffatalitiesinDutchtraffic(2004-

2008)was810in686registeredfatalaccidents.The

differencecanbeattributedtothefactthatthepolicedo

notregistereverythingandthattherecanbemorethanone

fatalityperaccident.Inaround15%ofallfatalaccidentsa

lorryisinvolved.Forhospitalisationsthisisbetween5%and

6%,which-giventhefactthatlorryaccidentsarebetter

registeredthanotheraccidents-exaggeratesthereal

picture.

Accidentsinvolvinglorriesaretherebymoreseriousthanthe

averageaccident,whichisunsurprisinggiventheirmassand

size[28,29].

InthedatabaseofregisteredaccidentsintheNetherlands

BRON,itisnotstatedwhethertheaccidentoccurredon

amotorway.Itappearstobedifficulttoascertainwhich

accidentscanbecountedasmotorwayaccidents.Whilethe

State(Rijkswaterstaat)isresponsibleforallthemotorways,

thisisnotthecasefornon-motorwayroads,asillustratedin

Figure20.

Bylinkingtheaccidentstothe‘currentlistofroads’(BRON

iscoupledtotheNationalRoadsdatabase)isitispossible

tosectmotorwayaccidents.Thisreveals,forinstance,that

eachyearonStateroads30fatalaccidentsoccurinvolving

lorriesonroadsections.Formotorwaysalonethefigure

is21(seeChart8).Sincetheincidenceoftrafficfatalities

isthemostcommontrafficsafetyindicator,onecansay

thataround3%ofthetrafficdangerrelatestoaccidents

involvinglorriesonmotorways,theaveragetotalbeing810

fatalitiesperyear.Onmotorwayintersectionstherearefew

accidentsinvolvinglorries,around1%ofthe2,700orso

roadsectionaccidentsannually.Thisisbecausemotorway

intersectionsarealwaysondifferentlevels.

Thetotalnumberofregisteredaccidentsinvolvinglorrieson

motorways,includingintersections,was2,334in2008.

Involvementdoesnotmean,ofcourse,thatthelorrycaused

theaccidentinsofarasonepartycanbeheldresponsible.

5. Study of the effect on safety

Figure 20: The Dutch principal road network (motorways in dark blue)

Final report Accident prevention systems for lorries4�

Bywayofillustration:ofthe106fatalaccidentsinvolving

lorriesonmotorwaysfrom2004to2008,thelorrywas

registeredasthefirstcollisionvehicle(“guilty”)in43cases,

62timesthesecondcollisionvehicleandonceneither

thoughinvolved.Theregistrationofmaterialdamageonly

accidentsisprobablyalittletoolowgiventhatthepolicedo

notgivethisregistrationanypriority.

Inacollisioninvolvingalorry,thedrivertendsnottobethe

(mostserious)victim;theratioisaround1to12,thatis11

trafficfatalitiesoutsidethelorryandoneinside.Thisratiois

differentonmotorways,around1to5,becausethereare

nocyclists,pedestriansormopedridersonmotorways.Each

yearsome10lorryoccupantsdie,4onmotorways.

On120kmroadstherehavebeen14lorrydriverhospitali-

sationseachyearsince2004(totalof70).Aquarter(3per

yearonaverage)comesfromabroad.

5.3 Relationship between APS and safety

TheeffectsofAPSonsafetyareinfluencedbymany

differentfactorsandimportantlyincludetheconductofthe

driver.Someofthesefactorshavebeenexplicitlyresearch

intheAPSfieldoperationaltest.Someactorshavenotbeen

studied,forinstancebecausethiswasdifficulttodoand

theythusfalloutsidethescopeoftheproject(forexample,

driverstatus).

InFigure18(Chapter4.1)therelationshipisshown

betweentheAPStypesandthevariousindicatorsthatwere

measured:speed,headwaytime,etc.Theseindicatorscan

beconsideredaselementsofthedrivingbehaviourofthe

driver.

Wemusttakeaccountintheanalysisofthefactthatthese

indicatorsarenotinfluencedsolelybyAPSbutalsobyvari-

ousotherfactors(seeFigure21).

Figure21revealsthattheeffectsofAPSonsafetyortraffic

flowareinfluencedbyanumberoffactorsdirectly(the

thirdcolumnincluding‘Drivingbehaviourofdriver’)andin-

directlysincetheyhaveaninfluenceonthe“directfactors”.

Thecoloursshowtheextenttowhichthefactorismeasu-

redinthetestasdirectorwhetherthetesttakesaccountof

thepossibleinfluenceofthisfactor.Thethickarrowsreveal

theaspectsthatwerethefocusofdirectstudyinthistest.

5. Study of the effect on safety

Chart 8: Accidents of varying degrees of seriousness on motorway road sections involving lorries

Seriousness of accident �004 �005 �006 �007 �008 Total (�004 - �008)

Fatal 24 20 22 20 20 106

Hospitalisation 106 111 100 117 93 527

FAO 109 125 106 122 107 569

Light 67 75 44 50 40 276

MDO 2.498 2.499 2.503 2.440 1.965 11.905

Total �.804 �.830 �.775 �.749 �.��5 �3.383

MDO(MaterialDamageOnly),FAO=FirstAidOnly

Final report Accident prevention systems for lorries 43

Driving behaviour of the driver:

Themeasurementsareameasureoftheactualdriving

behaviourofthedriver.

Driver features:

Theseincludethestablepropertiesofthedriver,likeage

anddrivingstyle,whilebeliefsarenotdirectlymeasured.

Giventhescaleofthetestitcanbeassumedthatany

differenceswillaverageout.

Type of lorry:

Thepropertiesofthelorriesareknown[27].

Surroundings:

Extremeinfluenceofthesurroundings(likeweather,road

works,trafficpicture)areincorporatedintheselectionof

dataforanalyse.

Driver status:

‘Driverstatus’isafactornotmeasuredinthisstudy.

Use:

Inmostofthesub-groupstheaccidentpreventionsystem

couldnotbeswitchedoff.TheACCcanbeswitchedoffbut

thisisnotlogged,justastheMobileyeinSP2.Therefore

thetestdidnotloghowthedriverwoulduse(otherAPS’or

used)ACCanysystem.Systemacceptancecanbedeter-

minedthroughinterviewsandquestionnaires.

5. Study of the effect on safety

Figure 21: Safety model

Driver features

Type of lorry

APS

Surroundings

Use

Driver status

Driving behaviour of others

Driving behaviourof driver

Route selected

Modality

Safety

Flow

Measures in test Account taken of

Not measured

Final report Accident prevention systems for lorries44

Route selected:

Itispossibletolookretrospectivelyattherouteselectedon

thebasisofGPSdata.ItcannotbemeasuredwhetherAPS

influencedtherouteselected.

Driving behaviour of others:

ThepossibleeffectofAPSonothertrafficparticipantsand

ontheselectedroutearenotmeasuredinthetest.

Modality:

NoeffectcanbeexpectedbyAPSonthechoiceofmodality

withinthecontextofthistest,soitwasnotmeasured.

InestimatingthesafetyeffectsofAPS,partialusewasmade

ofamethodologyusedearlierinaprojectlookingatthe

socio-economiceffectsofintelligentvehiclesafetysystems:

theeIMPACTproject[13].

However,inviewofthefactthatinsufficientclaritystill

existsabouttheexactrelationshipsbetweenbehaviour

variablesandtheriskofanaccident,theconclusionsinthis

reportarelimitedlargelytoqualitativeeffectsandbroad

estimatesofquantitativeeffects.

Foradetaileddescription,thereaderisreferredtothe

reportentitled‘Conceptualmodelofsafety’[17].

TheeIMPACTstudyidentifiedninebehaviourmechanisms

onwhichdriverassistancesystemscanhaveaneffect.Each

mechanismcanresultineitherpositiveornegativeeffects

ontrafficsafety.Withinthecontextofthefieldoperational

twomechanismsareimportant:

• Directin-carmodificationofthedrivingtask

- Thesearethesystem’sdirecteffects,i.e.direct

reactionstothesystem’soutput.Forexample,the

systemcanhaveaneffectonthedriver’smental

workloadorensurethatthedriverbrakes.These

directeffectscanbebothintentional(forexample:

longerheadwaytimes)andunintentional(for

example:distractionbythesystem).

• Indirectmodificationoftheuserbehaviour

- Theseareeffectscausedbythedriver’sadaptation

tothechangingsituation,namelydrivingwiththe

system.Ingeneral,theseeffectsaredifficultto

predictandittakessometimebeforeadriver

hasdevelopedsuchbehaviouraladaptation.

Examplesofunintentionaleffectsareadecrease

inheadwaytimecausedbyanincreasedfeelingof

safety,distraction,etc.

TheSWOVdatabaseoflorryaccidentsusesthefollowing

accidentcategories:

• Collisionwith:pedestrian,parkedvehicle,animal,

attachedobject,unattachedobject;

• Frontalcollisions;

• Sidecollisions;

• Rear-endcollisions;

• Single-vehicleaccidents.

5. Study of the effect on safety

Final report Accident prevention systems for lorries 45

FortheexpectedeffectofAPSontrafficsafetythelorry

mustbeseenasthe‘cause’oftheaccidentsoitisimportant

foratleastthesideandrear-endcollisionstorecognisethe

lorryas“firstcollisionvehicle”(‘cause’).

ThepercentagesinChart9concernallaccidentsinvolving

lorriesonmotorways,alsowherethelorryisnotthefirst

collisionvehicle.Inaroundhalfofallseriousaccidentsthe

lorryisthefirstcollisionvehicleandformaterialdamage

onlyaccidentsthisshareishigher.Thereasonisthatmulti-

pleaccidentsinvolvinglorriesarerelativelysevere.Single-

vehicleaccidentstendtoinvolvematerialdamageonlyor

slightinjuryandthelorryisinsuchcases,indeed,always

thefirstcollisionvehicle.

Fromtheabove,theaccidentcategorieswereselectedon

whichthetestedsystemscouldhaveaneffect.Theseare:

• Frontalcollisions(FCW/HMW,ACC,DC,LDWA,

BBFB);

• Sidecollisions(LDWA,DC,BBFB);

• Rear-endcollisions(FCW/HMW,ACC,BFBB);

• Single-vehicleaccidents.(LDWA,DC,BFBB).

Figure21shows,amongotherthings,thegeneralrelation-

shipbetweenbehaviourindicatorsandsafety.

Thisgeneralrelationshipisdetailedbelowintermsofwhich

behaviouralcomponentrelatestowhichtypeofaccident.

DifferentAPScanhavedifferenteffectsonsafetyandsoon

differentkindsofaccidents.TheeffectsofAPSonspecific

indicatorscanbecategorisedintothetypeofaccident.

Chart10showsperindicatoronwhattypeofaccidenta

changeinthisvariablecanhaveaneffect.

5. Study of the effect on safety

Chart 9: Nature of accidents on motorways involving lorries as first col-lision vehicle

Chart 10: Summary of accident types whereby measured variable has an effect

Nature of accident

Total �004-�008

%

Fatal side 4 4%

rear-endcollision

25 24%

Hospitalisation side 49 9%

rear-endcollision

105 20%

FAO side 88 15%

rear-endcollision

154 27%

Lightinjury side 49 18%

rear-endcollision

77 28%

MDO side 2.698 23%

rear-endcollision

2.148 18%

Measured variable Frontal Side Rear-end collision Single vehicle

Headwaytime

Frequencyofshortheadwaytimes

Speedvariation

Averagespeed

Line-breachfrequency

Largeacceleration/deceleration

Distancetolanemarking

Final report Accident prevention systems for lorries46

Alongthehorizontalaxisthekindofaccidentsareshown

andalongtheverticalaxisthevariable.Ifanareaisblue,

thismeansthatthevariableaffectsthattypeofaccident.If

theareaisblank,thennoinfluenceisassumed.

DifferentvariableareusedtoestimatetheeffectsofAPS

ontrafficsafety,themainonebeingspeed,speedvariation,

headwaytimeandfrequencyofLDWAwarnings.

Forspeedandspeedvariationformulasareknownfrom

literaturethatcancalculatetheeffectofachangeinthese

variableonthenumberofaccidentsortheriskofan

accident.Fortheothervariablesonlycriticalvaluesare

knownandnothowanychangeinthesecriticalvalues

influencestheriskofanaccident.

ThismeansthataquantitativeeffectperAPScanbeesta-

blishedpurelyonthebasisofpossiblechangesinspeedand

speedvariation.However,onlyaqualitativeeffectcanbe

establishedonthebasisofchangesintheothervariables.

5.4 Estimating the effect on safety using

a model

Basedontheconceptualmodelofsafetyboththequalita-

tiveandquantitativeeffectsofAPSonsafetywereestima-

tedaswellaspossible.Inthischapteranoverviewofthese

effectsispresentedforeachsystem.Whereknownfrom

eIMPACT[13],theeffectsofsimilarsystemsonsafetyare

reported.Chart11showsanoverviewoftheeffectsofeach

APSonthemeasuredvariablesexpressedinpercentage

decreaseorincrease.

Basedonthesepercentages,thefoundeffectsonsafetyof

eachsystemaresubsequentlydescribed.

DC/ROC

DC/ROCisassumedtohaveaneffectontrafficsafety.

BasedonNilsson’sformula[17],inwhichtherelationship

betweenchangeinspeedandnumberofaccidentsisdescri-

bed,itwascalculatedthatadecreaseintheaveragespeed

of2%resultsinadecreaseinthenumberoffatalaccidents

of5%.Thiseffectappliestoalltypesofaccident.

5. Study of the effect on safety

Chart 11: Summary of measured effects of APS on behavioural variables

DC/ROC ACC LDWA FCW/HMW BBFB

Average headway time NSD 6%increase NSD NSD X

Percentage of short headway times (< � s)

NSD 3.2%decrease SP3b:5.9%increase

NSD X

Speed variation (standard deviation)

14%decrease NSD NSD NSD Haulier1:24%decrease

Haulier2:5%increase

Average speed 2%decrease NSD NSD NSD NSD

LDWA frequency warnings

NSD 35%decrease SP1:30%decrease

SP3b:62%decrease

NSD X

NSD=NoSignificantDifference,X=NoMeasurements

Final report Accident prevention systems for lorries 47

ThedecreaseinspeedvariationwiththeuseofDCwastoo

minortobringaboutaneffectontrafficsafety.Moreover,

itcannotbeattributedtotheuseofDC,butismorelikely

tobeduetothetypeoflorrythatdriveswithDCandthe

driver(tanktransport).DCisalsotypicalofasystemthat

intervenesincertaincriticalsituationsandthuswhichoften

preventsapotentialaccident.Theseinterventionswerenot

measuredinthetest.

TheeIMPACTstudyconcludedonthebasisofearlier

studiesthatESC(anotherformofDC/ROCandmuchused

incars)woulddeliverintotalareductionof16.5%inthe

numberoffatalaccidentsand6.5%inthenumberof

accidentswithcasualties(eIMPACT,2008).

ACC

LookingattheeffectsofACCaspresentedinChart11,

aminortoreasonableeffectofACCisassumedontraffic

safety.Adecreaseinthepercentageofshortheadwaytimes

impliesadecreaseinthenumberofrear-endcollisions.A

decreaseinthenumberofcriticalheadwaytimescanhave

afavourableeffectonalltypesofaccident.Adecreasein

thenumberofLDWAwarningswithACChasafavourable

effectonthenumberofflankandone-vehicleaccidents.

TheeIMPACTstudyconcludedonthebasisofearlierstu-

diesthatACCwoulddeliverintotalareductionof1.0%in

thenumberoffatalaccidentsand3.5%inthenumberof

accidentswithcasualties(eIMPACT,2008).

LDWA

BasedonaconsiderabledecreaseinthenumberofLDWA

warningsasshowninthetable,LDWAisexpectedtohave

aneffectontrafficsafety,i.e.adecreaseinthenumberof

flankandone-vehicleaccidents.

TheeIMPACTstudyconcludedonthebasisofearlier

studiesthatLDWAwoulddeliverintotalareductionof

15%inthenumberoffatalaccidentsand11%inthe

numberofaccidentswithcasualties(eIMPACT,2008[13]).

FCW/HMW

BasedonthedatanoeffectofFCW/HMWontrafficsafety

isexpected.However,inChapter4.4intheanalysisofa

partofthedata,apositiveeffectismeasuredatminimum

headwaytimeontrafficflow.

BBFB

DespitethefactthatwiththeuseofBBFBbothadecre-

aseaswellasaveryminorincreaseinspeedvariation

wasfound,itcanbeconcludedbasedontheformulasof

Salusjärvi[16],inwhichtherelationshipbetweenchangein

speedvariationandnumberofaccidentsisdescribed,that

thesechangeshavenoeffectontrafficsafety.

5. Study of the effect on safety

Final report Accident prevention systems for lorries48

5.5 Number of accidents observed

Onlyfiveaccidents(withmaterialdamageonly)were

registeredorreportedduringthemeasuringperiodandall

fivewereinthereferencegroupwherebythedriverisnot

informedbutonlydatareadingsaretaken.Enquiriesamong

therespectivehauliersgeneratednootherfiguresforthea

numberofaccidents.

Theexpectednumberofaccidentscanbederivedinvarious

ways.

Firstly,thepopulationratios.

• Thegroupofvehiclesmonitoredisaround1%ofthe

totalpopulationoflorriesonDutchroads.

• Themeasuringperiodis8months.

• In20082,334accidentsinvolvinglorriesonmotorways

(see5.2),includingintersections,wereregistered.

• Basedonthepopulationratiosome16accidentscan

beexpected.

Secondly,themeasuredquantityofvehiclekilometres.

• In20082,334accidentsinvolvinglorriesonmotorways

(see5.2),includingintersections,wereregistered.

• Rijkswaterstaatreportsindicatethatin200863billion

vehiclekilometresweredrivenonmotorways.

• 15%wasdrivenbylorries:thisisaround9.45billion

vehiclekilometres.

• Thepopulationmonitoreddrove77millionkilometres

intheNetherlands.

• Basedontheseratiossome19accidentscanbe

expected.

Thereferencegroupissome30%ofthetotalfieldopera-

tionaltest,soaround6accidentscanbeexpectedinthis

group.Theactualnumber,5,deviatesverylittletherefore.

Therelativelylownumberofregisteredaccidentsisnot

predictedonthebasisofthemeasurementsoftheeffectsof

APSinthefieldoperationaltest.Thoseeffectsarereallynot

solargethattheycoulddirectlyexplainsuchadifference.

Intheoryotherexplanationsareconceivable.Forinstance,it

couldbethatthedriveswhoknewtheywereparticipating

inanaccidentpreventiontesttookthisintoaccountintheir

drivingbehaviour.Ontheotherhand,allthedriverswere

awareoftheirparticipation,eventhoseinthereference

group.

Furtherresearchisdesirabletoinvestigatethecauses,forin-

stancebymonitoringtheaccidentsinthisgroupforalonger

periodoftimeandanalysingthedatafurther.

5. Study of the effect on safety

Final report Accident prevention systems for lorries 49

6.� Literature study

Theaccidentpreventionsystemscaninfluencetrafficflow

intwoways:viaaneffectonthedriver’sregulardriving

behaviourandviaaneffectonthenumberofaccidents,

whichinturncancausetrafficjams.Thesearereferredto

asdirectandindirecteffectsrespectively.Ingeneralitis

evidentfromtheresultsofthisliteraturestudythateachof

thesystemshasapositiveeffectontrafficflowbycausing

thenumberofaccidentstodecline.Theliteratureisnot

unequivocalabouttheextenttowhichthisoccursandthe

equipmentlevelthatisnecessarytoachievethiseffect.

Astotheeffectsontrafficflowachievedthroughan

adaptationofregulardrivingbehaviour,thesourcesare

virtuallyunanimouswithregardtoLDWA:theeffecton

trafficflowthatcanbeexpectedwiththissystemisnoneat

alloratmostasmallpositivedirecteffect.Forthesystems

BBFB,DC,FCW/HMWnostudieswerefoundthathave

conductedresearchintothedirecteffectsontrafficflow.

Forthemostpart,apositiveeffectwasfoundforACC,

undercertainconditionsfortheequipmentlevelandsystem

settings(forheadwaytimesinparticular).Owingtohomo-

genisation,thelanecapacityincreasespotentiallybya

coupleofpercent,providedthepresetheadwaytimeis

sufficientlylow.ItmaybethatamixofACCandnon-ACC

vehiclesisrequiredtoachievethemaximumeffect.Inaddi-

tion,ACCtypesspeciallydesignedfortrafficjamdrivingcan

limitthetimelostintrafficjamsby30%to60%andraise

theoutflowfromtrafficjamsby7%.

Tosummarise,thefollowingisstatedintheliterature:

• AllfiveAPShaveapositiveindirecteffectontraffic

flowsincetheycausethenumberofaccidentsto

decline.

• Apositivedirecteffectontrafficflowachievedthrough

theadaptationofdrivingbehaviourisassumedfor

ACConly,undercertainconditions.

• ForBBFB,DCandFCW/HMWnoresultsconcerning

directtrafficflowwerefound.

• ThedirecteffectofLDWAappearstobeneutral,or

potentiallyslightlypositive.

6.� Model

Theconceptualmodeloftrafficflowtranslatestheimpact

ofAPSondrivingbehaviour(establishedonthebasisof

theactualdata)intoaneffectonlanecapacity.IntheAPS

projectitwasdecidedtoworkwithaversionofthefun-

damentaldiagrammethod.Thismethodwasusedintwo

ways:inahypotheticalscenarioexclusivelywithlorries,and

inamorerealisticscenarioinvolvingmixedtraffic.Bothsce-

nariosarepresentedinFigure22.Foralargerpresentation

ofthetwovisualsaccompaniedbytextandexplanatory

notes,thereaderisreferredtoAppendix3.Theconceptual

modelisdescribedinmoredetailin[12].

DatafromtheAPStestareshownintheblueboxes.Data

fromothersources[Monicadata,13,14]areshownin

yellowboxes.

Thetwoscenariosarerepresentedinthetwodiagrams.

Thetwoscenariosarerepresentedinthetwodiagrams.In

theleftdiagram(exclusivelylorries)arelationshipbetween

theheadwaytimeandspeedoflorriesissoughtbasedon

theactualdata.Fromthisrelationship,theminimumhead-

waytimecanbederivedandthenlanecapacityestimated

forthehypotheticalsituationoftrafficcomprisingexclu-

sivelylorriesequippedwithAPS.Tomakesuchanestimate,

datafortrafficathighintensity,inparticular,arenecessary.

6. Study of the effect on traffic flow

Final report Accident prevention systems for lorries50

Giventhatlorriesdrivepredominantlyatlowtrafficinten-

sity,withaconsiderableheadway(twosecondsormore),

aselectionwasmadefortheanalysiswherebymeasuring

pointswithshortheadwaytimeswerechoseninorderto

derivetherelationshipbetweenheadwaytimeandspeed.

Theright-handdiagram(mixedtraffic,i.e.,equippedand

non-equippedlorriesandothertraffic)presentsafunda-

mentaldiagramforthereferencesituationonthebasisof

datafrommeasuringloops.Fortheprojectsituationthe

datapointsweremodifiedbasedonthetestdata.Eachdata

pointinthereferencesituationisthusshiftedandanew

diagramcreated.Thecapacityisthemaximumintensity

accordingtothisdiagram.

6.3 Traffic flow effects as a result of change

in driving behaviour

Accidentpreventionsystemsmayhaveaninfluenceonthe

drivingbehaviourofthedriver,whomayoptforadifferent

speedorheadwaydistanceoramoreconstantdrive.Ifa

largenumberofvehiclesisequippedwithAPS,thesechan-

gescanhavenoticeableconsequencesforthetrafficflowof

thetotaltraffic.Thenumberofvehiclesparticipatinginthe

testwasfartoofewcomparedtothetotaltrafficstreamto

generateadirecteffectontrafficflow;congestionwould

notbereduced.Forthisreason,trafficfloweffectswerenot

determineddirectlyfromthetest,butwiththeaidofacon-

ceptualmodel(see3.3.2).Thismodeldescribestheimpact

ofthesystemondrivingbehaviourbasedontheactualdata

andtranslatesthisintoeffectsontrafficflow.Theeffect

6. Study of the effect on traffic flow

Figure 22: Conceptual model of traffic flow (both diagrams are explained in appendix 3)

Conceptual model

Speeds with and without system

Net headway times withand without system

Lorry length

Share of lorry traffic (Y)

Penetration levelAPS (X)

Gross headway times withand without system

Speed and intensity of traffic without system

Fundamental diagram method,mixed traffic

Fundamental diagram method, freight traffic only

head

way

tim

e

speed

intensity

spee

d

- equipped- non-equipped

- equipped- non-equipped

change in capacity

trafficcapacity

traffic without system

traffic with system

change in capacity

Maximum capacity change with freight traffic only

Capacity change withmixed traffic

Final report Accident prevention systems for lorries 5�

isexpressedinlanecapacity,i.e.themaximumnumberof

vehiclesthataroadsectioncanprocessinanhour.

Thisinvolvedmakinganumberofassumptionsandchoices:

• APShasaneffectonlyonaspectsofdrivingbehaviour,

suchasthechoiceofspeed,laneandheadwaytime.

APShasnoinfluenceonstrategicdrivingbehaviour

andtranspositionchoice.ThepossibleeffectofAPS

onthedrivingbehaviouroftheothertrafficwasnot

included.

• AswellasAPS,therearemanyexternalconditions

thatcaninfluencedrivingbehaviourortheeffective-

nessofAPSsystemssuchasroadtype,weatherand

load.Theseconditionsweretakenintoaccountasfar

aspossibleintheanalysisandset-upofthetest,but

forpracticalreasonsnotallconditionswereincludedin

theanalysis.

• TheeffectofAPSonlanecapacityisproportionalto

thenumberofequippedvehicles(ormoreprecisely

withthepenetrationlevel),i.e.nointeractioneffects

wereincluded2.

• Effectsatnetworklevel(networkcapacity,journeytime

losses)werenotincluded.

• ForACConlytheeffectofownershipwasdetermined,

nottheeffectofuse.

• Onlysignificantdifferencesevidentfromtheactual

datawereincludedintheanalysis.

Asexplained(figure22,conceptualmodeloftrafficflow)

aneffectonlanecapacityhasbeenderivedintwoways:

forahypotheticalsituationwith(equipped)freighttraffic

onlyandforthesituationwithmixedtraffic(equippedand

non-equippedandothertraffic).Sincethefirstmethod

usesaselectionofdata(namelythedataelementswith

shortheadwaytimes)andthesecondmethodusesalldata,

themethodsmaydeliverdifferentresults.Inthatcase,the

secondmethodshouldberegardedasthemostreliable,and

thefirstusedonlyindicatively.

Results of the ‘freight traffic only’ analysis

• LDWAhadanegligibleeffectontheminimumhead

waytimefornon-tanklorries:dependingonthelorry

typeintheSP,theminimumheadwaytimeincreased

ordecreasedduetoLDWAbylessthan0.1second.

• FCW/HMWcausedanincreaseintheminimumhead

waytimeforanarticulatedlorry:inthereferencethis

was0.062sec,withFCW/HMW0.2sec,anincrease

of0.14sec(228%).Thediagramshowingthisresult

canbefoundinFigure23.

• ACChadaminoreffectonnon-tanklorries.The

minimumheadwaytimefellfrom0.44secto0.31sec,

adecreaseof0.13sec(29%)oraround3metres’

distanceat80km/h.

InFigure23theheadwaytimesofvehiclesequippedand

notequipped(reference)withFCW/HMWaresetagainst

theaveragespeed;thesearerepresentedbythecrossesand

circlesinthefigure.Forbothequippedandnon-equipped

vehicles,thefourth-degreepolynomialisthenshownthat

providesthebestmatchwiththeminimumheadwaytimes,

theblueandpinklinesinthefigure.

2 This is a frequently made assumption in FOTs, stemming from the fact that it is not known what happens to the non-equipped traffic that is confronted with equipped vehicles.

6. Study of the effect on traffic flow

Final report Accident prevention systems for lorries5�

TomakeFigure23clearerthesamedataareplottedinFigu-

re24butwithheadwaydistancesetagainstaveragespeed

andtheheadwaytimesconvertedintoheadwaydistances.

Whatisnoticeableishowshorttheheadwaydistancecan

beatspeedsintheregionof70to90km/h.Secondly,it

isclearthatFCW/HMWintheaverageheadwaytimehas

atangiblepositiveeffectwhilethatwasnotvisibleinthe

percentageofshortheadwaytimes(<1s).

DCisusedmostlyoncontainerlorries.ForDCtoofewdata

pointswereavailabletomakereliablejudgementsabout

headwaytimesand,thus,trafficflow.

However,itisexpectedthatdriversoftankerswillkeep

longerheadwaydistancesandthuslongerheadwaytimes

duetotheirsaferdrivingbehaviour.Thisisduetothetype

oflorry,however,nottoDC.

Results of the ‘mixed traffic’ analysis

For‘mixedtraffic’itwasnecessarytochoosethenumber

ofequippedlorriessincetheeffectofAPSonlanecapacity

dependsonthenumberofequippedlorries.TheAPSpene-

trationlevelisdefinedasthefractionofthetotalnumber

oflorrykilometresonDutchroadstravelledbyavehicle

equippedwithAPS.

Thepenetrationlevelinthetestwastoolowtohaveany

effectonthetrafficsystem.Forthisreason,theanalysisof

thetrafficfloweffectswasperformedforpenetrationlevels

choseninadvance.Todeterminetheeffect,theproject

situationwascomparedwithareferencesituation.Forthe

referencesituationtheAPSpenetrationlevelwassetat0%,

i.e.noneofthelorriesisequippedwithAPS.Fortheproject

situationtwoscenarioswereinvestigated:onewith100%

penetration,andonewiththepenetrationlevelsshownin

Chart12.

6. Study of the effect on traffic flow

Figure 23: Effect of FCW/HMW on articulated lorry (freight traffic only scenario)

Figure 24: Effect of FCW/HMW on articulated lorry (freight traffic only scenario), with headway times set against average speed

Chart 12: Penetration level

Effect FCW/HMW Articulated Lorry

Hea

dway

tim

e [0

.1*s

]

Average speed [km/h]

Average speed [km/h]

Hea

dway

tim

e [0

.1*s

]

Effect of FCW/HMW on articulated lorry

Headway times referenceHeadway times equippedFourth-degree best fit polynomial equippedFourth-degree best fit polynomial reference

APS ACC LDWA FCW/HMW BBFB

Penetration level 25% 50% 50% 25%

Final report Accident prevention systems for lorries 53

SinceitishighlylikelythateffectsfoundforDCwouldnot

beattributabletoDCbuttothetypeoflorryandthedriver,

DCwasnotincludedintheanalysis.

Thesepenetrationlevelswerebasedasfaraspossibleona

projectiontakenfromeIMPACT3[13]ofthepenetrationle-

velofanumberofsystemssimilartoAPSintheyear2020.

ForACCasignificanteffectonheadwaytimewasfound,

andforDCasignificanteffectonspeedwasfound.Itis

possible,therefore,thatthesetwosystemshaveaneffect

onlanecapacity.Fortheothersystemsnosignificanteffect

onheadwaytimeorspeedwasobservedandthusnosigni-

ficanteffectonlanecapacitycanbeexpected.

ForACCtheeffectonlanecapacitywasdeterminedwith

theaidofthefundamentaldiagram.

Thisassumesashareoffreighttrafficof15%[14](i.e.that

15%ofthevehiclekilometresontheDutchmotorwaysis

drivenbylorries).Thefundamentaldiagramcompletewith

actualdatameasuredbetweenhectometrepoles40and

45ontheA2isshowninFigure25.Thevehicleintensity

isshownonthehorizontalaxisasnumberofvehiclesper

hour(Vgt/u),withtheaveragespeedofthevehiclesonthe

verticalaxis.Thebluedotsshowtheactualdatafromthe

test;intensityissetagainstaveragespeed(thefundamental

diagram).Twolineshavebeenplotted:theblacklineforthe

referencescenarioandthegreenlineforthescenariowith

100%penetration.Themaximumofthecurveisthelane

capacity.

TheresultsaresummarisedinChart13.Anegativepercen-

tagemeansadecreaseinthelanecapacity.

Togiveanideaofthepercentages:aneffectof-0.58%

with100%ACConathree-lanemotorwaymeansacapa-

citydropof30vehiclesanhourforatotalof1,700vehicles

perhourperlane.

3 In the eIMPACT European project (concluded in 2008) an impact assessment was performed for 12 safety systems. Penetration levels for these systems were estimated for the years 2010 and 2020.

6. Study of the effect on traffic flow

Figure 25: Effect of ACC on lane capacity on a 3-lane motorway (blue dots: actual data; black curve: reference scenario; green curve: scenario with 100% penetration)

Chart 13

Fundamental diagram A2 right-hand lane 40 - 45 km

Intensity (Vtg/h)

Ave

rage

spe

ed [

km/h

]

APS Penetration level

Effect on lane capacity as function of penetration level

and number of lanes

Motorway, �-lane

Motorway, 3-lane

ACC 25% -0.14% -0.15%

100% -0.56% -0.58%

Final report Accident prevention systems for lorries54

Conclusions:

• Itisevidentfromthe‘mixedtraffic’analysisthatfor

ACCtheeffectonlanecapacityisveryminorand

negative,evenat100%penetration.

• Fromthe‘freighttrafficonly’analysisitfollowsthat

LDWAhasanegligibleeffectonlanecapacity

• Fromthe‘freighttrafficonly’analysisitisevidentthat

FCW/HMWcausesanincreaseintheminimumhead

waytimeandthatACCisresponsibleforadecreasein

theminimumheadwaytime.

Thefollowingcommentshouldbemade.Withtheuseof

ACC,lanecapacityreduces.Thisappearstocontradictthe

resultfoundearlierthattheminimum headwaytimeredu-

ceswithACC.However,theaverageheadwaytimerises

withACC,causingthelanecapacitytodiminish.

Indevisingtheconceptualmodel,assumptionsweremade.

Thismeansthatthereisatolerancewithregardtothe

outcomes.Thistoleranceisprobablygreaterthanthecal-

culatedeffects.Tosummarise,itdoeshoweverremainvery

plausiblethatachangeindrivingbehaviourduetotheuse

ofAPShasnotoatmostaminornegativedirecteffecton

lanecapacity.Bymeansofareductioninthenumberofac-

cidents,however,anindirectpositiveeffectcanoccur.This

isdiscussedinthefollowingchapter.

6.4 Traffic flow effects as a result of accident

Accidentpreventionsystemsmayreducethenumberof

vehiclehourslostasaresultoftrafficjamscausedbyacci-

dents.Thiseffectisdividedintoaprimaryeffect(trafficjam

upstreaminthesamelaneaswheretheaccidentoccurred)

andsecondaryeffects(knock-onofthejamtootherhigh-

waysandonlookerjams).

ToestablishthetrafficfloweffectsofAPS,itisessentialto

identifythevehicletimelostcausedbyalorryaccident.To

dothisinformationregardingaccidentsonthemotorwayin

2007(registrationofincidentsfromtheMonitoringIncident

ManagementprogrammebyDVS)waslinkedtoinforma-

tionregardingtrafficflow(Monicadata).

Thenumberofhoursofvehicletimelostwasdetermined

foreachaccident.Naturally,itisrecognisedthatthisvehicle

timelostcannotbeattributableinallcasestotheaccident

-therearealwaysnormaltrafficjamstoconsider.Therefore,

thetimelostnotcausedbytheaccident(the‘reference

situation’)wassubtractedfromthetotal.

Aggregatingtheeffectsoftheindividualaccidentsresults

inthetotaldirecteffects.Thesedirecteffectswerescaled

upsincetheavailabledatadidnotbydefinitioncomprise

allaccidents(thesedataweresometimesnotregisteredin

theirentiretyandthecalculationreliedonarepresentative

numberofaccidentsfrom2007).Asubsequentupscaling

tookplaceforthesecondaryeffectsreferredtoabove.

Theupscalingfactorsusedweredeterminedstatisticallyon

thebasisofseveralcases.Adetaileddescriptionofthe

methodandtheresultscanbefoundin[15].Onlythe

6. Study of the effect on traffic flow

Figure 26: Relation between accidents and hours lost

Hours lost

Accidents

Traffic jams caused byaccidents

Final report Accident prevention systems for lorries 55

motorwaywastakenintoconsideration.Asaresult,the

repercussionsforthesecondaryroadnetworkwereunde-

restimated.

Thecalculationfor2007showsthatround1.1millionvehi-

clehourswerelostduetolorryaccidentsonmotorwaysin

theNetherlands,some1.6%ofthetotalvehicletimelostin

thatyearontheseroads.Naturally,thereisnopossibleway

alltheselorryaccidents(andthusthesevehiclehourslost)

canbepreventedbyAPS.

Fromsection5.2nogoodunequivocalfigurefollowsforthe

reductioninthenumberofaccidentsperyear.Tobeableto

estimatetheeffects,3scenarioshavebeencalculated.

Todothis,twoassumptionsweremade:

• TheaccidentsthatAPScanpreventconcernalllorry

accidents,i.e.allaccidentsinwhichlorriesareinvolved.

Thesearebothaccidentscausedbylorriesand

accidentswithanothercause.

• TheaccidentsthatAPScanpreventareevenly

distributed;i.e.theycausean‘average’numberof

vehiclehourslost.Areductionof1%inthenumberof

lorryaccidentsinoneyearcausesareductionof1%in

thevehiclehourslostinthatyearbylorryaccidents.

Theresultsforvariousaccidentreductionpercentagesare

showninChart14.

6. Study of the effect on traffic flow

Chart 14: Saving in terms of vehicle hours lost as a result of fewer accidents

Reduction in number of accidents (%)

Effect on vehicle hours lost

-5% -55.000

-10% -110.000

-15% -165.000

Final report Accident prevention systems for lorries56

Bothdriversandcompanieswereaskedabouttheirex-

periencesofusingtheaccidentpreventionsystemsand

whethertheybelievedthesystemshadapositiveeffecton

theirdrivingbehaviour.Almost400questionnaireswere

completedand280interviewsheld,dividedoverthevarious

sub-projects.

Allparticipatingbusinessownerswereaskedtosubmita

companyprofilesothattheresultsofinterviewsandonline

surveys,etc,couldbesetintherightperspective.73busi-

nessowners(65%)submittedtheprofiles.

Finally,interviewswiththebusinessownerswereheldin

whichrepresentativesofmostoftheparticipatingcompa-

nieswereaskedtogivetheiropinions.Thebusinessowner

sessionsdrewatotalof30hauliersandOEMstogetherto

shareexperiencesandopinions.Onlinesurveys[22]and

face-to-faceinterviews[21]enabledthedrivers’opinions

tobecollectedwhileanonlinecompanyprofileform[24]

andcompanysessions[25]generatedinformationaboutthe

participatingcompaniesandtheirexperienceswithAPS.

7.� Results of driver surveys

Thefeelingsoftheparticipatingdriverstowardsthesystems

testedintheFOTrangedmostlyfromneutraltopositive.

Variousopinionsandexperiencesofeachsystemwere

stated,asshowninFigure27andFigure28.Inparticular,

driversdrivingwithACCfeltpositiveaboutthesystem.

Thedriversintheliquidbulksegmentwerethemostpo-

sitiveaboutthesystemtheydrovewith.Inthetest,most

driversinthissegmentdrovewithACCorDC.Thedriver

attituderesultscanbedividedintotwocategories.

Thefirstcategoryrelatestothepresettingofthesystems.

Thesecondcategoryconcernsuserexperience.Many

driversareirritatedbythenumberofalarmsandthetypeof

signalgivenbyvariousoftheAPS.Intheinterviewsalmost

80%ofthedriversmentionedfalsealarms.

Themajorityofeventsregardedasfalsealarmsactually

arosefromthestandardsettingchosenforthepurposesof

theFOTresearchaims.Inpracticethissettingmeant,for

example,thatLDWAissuedanalarmfor‘touchingthe

roadlines’andFCW/HMWraisedthealarmifthelorry

7. Study of incentives to use APS

Figure 27: Driver opinion per system

Figure 28: Driver opinion according to type of transport

very positivepositiveneutralnegativevery negative

positiveneutralnegative

liquid bulksolid bulk

hazardous load exceptional

Final report Accident prevention systems for lorries 57

approachedthevehicleinfrontwithaheadwaydistanceof

2seconds.

Inpractice,thesesettingswouldevidentlybeconsidered

verystrict.Forexample,thechanceoftheLDWAissuing

falsealarmswouldbeveryhighonaroadwithreduced

lanewidthduetoroadworks.Thisprompteddriverstofeel

irritated(whichwasexpressedbysabotageefforts,among

otherthings).DriversdrivingwithACCexperiencednofalse

alarms.HowpleasantdriversfeltacertainAPStobecan

bederivedfromtheirexperienceofthesystem’spresetting.

OnaVanderLaanscale[22]thisissetagainstasystem’s

usefulness.

Figure30showsthatthedriversdidnotalwaysfindanAPS

pleasanttousebutthatallsystemswereconsidereduseful.

Aquarterofthedriversthoughttheywoulddrivemore

safely.

Thesub-groupofdriverswithACCisanexception:two-

thirdsbelievedthattheywoulddrivemoresafelywith

ACC.Thereisnolinkbetweentheageorexperienceofthe

driversandtheiropinion.

Figure31showswhetherdriverswishedtocontinuedriving

withAPSattheendofthestudy.OfthedriverswithACC,

90%agreedwiththisstatement.

Fortheothersystems,30%to70%ofthedriverssaidthey

wantedtocontinuedrivingwithAPS.

FortheBBFBthedrivers’responsesappearedevenlydivided

betweentwoextremes:‘agree’to‘stronglyagree’and

‘stronglydisagree’.34%ofthedriversfeltthatalldrivers

shouldbedrivingwiththeAPStheythemselvesused.But

24%feltthiswasnotworthwhile.Almosthalfthedrivers

wereneutralonthispoint.

7. Study of incentives to use APS

Figure 29: Driver reaction to type of audio signal depending on type of APS

Figure 30: Acceptance: ‘pleasant’ versus APS ‘usefulness’

sound felt as disruptive sound not felt as disruptive

Plea

sant

Useful

Final report Accident prevention systems for lorries58

7.� APS from a business owner perspective

Theexperiencesrelatedtobusinessownersbytheirdrivers

matchthefindingsofthequestionnairesandinterviews.

Fortheretrofitsystems,scopeforflexibleadjustmentwas

voicedasbeingveryimportantinviewoftherangeof

drivingstyles,theworkcarriedoutbythelorryandthe

needtopreventfalsealarms.

Forallsystemsthebusinessownersstatedthattheyare

robustenoughtooperateinthelorries;thereishardlyany

incidenceofsystemfailure.

Asfarastheoperationofsystemsisconcerned,itisnoted

thatthetypeofsignalissuedtothedriverneedsfurther

consideration.AloudaudiblesignalasusedduringtheFOT

isirritating.Driveracceptancemaywellbeincreasedbya

differentaudiblesignalorsomeothertypeofsignal(e.g.a

lightsignal).Inaddition,businessownerssaidthatsystems

haveagreatereffectatcertaintimes.Driversseemtofeel

thesystem’saddedvalueismostevidentlaterintheday

andatnightorduringlongertrips.Noeffectswerereported

ormeasuredintermsoffuelconsumption.

Virtuallyalltheparticipatingcompanieshaveindicateda

desiretocontinueusingthesesystemsaftertheendofthe

test.Atleast7companieshaveindicatedthattheywill

extenduseofAPStolorriesnotcurrentlyequippedwith

thesystem.Thereststillwanttohavemoreinsightintothe

costs-benefitsanalysisofthesesystems.

Fromthereactionsofthecompaniesitcanbeexpectedthat

basedpurelyonoperationsthekeycriteriafortheuseof

APSare:

• Correctoperationofthesystemandflexiblesetting;

• AproveneffectofAPSontrafficsafety;

• Noadversecosts-benefitsratioforAPS;

• ClearexplanationupondeliveryofAPStothedriver

andcompanysothattheyarecognisantofthe

operationandpurposeofthesystem;

• Acceptanceofthesystemsbythedrivers(inpart

dependentontheexplanationofthecorrectoperation

ofthesystem).

7. Study of incentives to use APS

Figure 31: Does the driver wish to continue with APS after the test?

strongly agreeagreeneutraldisagreestrongly disagree

Final report Accident prevention systems for lorries 59

Effect on driving behaviourThefieldoperationaltestrevealsthataccidentprevention

systemshaveavarietyofeffectsonthedrivingbehaviour

ofthelorrydriver.Whiletheseeffectsmaybesmall,they

arestatisticallysignificant.Thismeansthatthetestcontains

asufficientquantityofdatatobeabletorevealsuchsmall

effects.Inotherwords,ifnotAPSeffectcouldbederived

fromthedata,thenthelikelihoodisthattheeffectwas,

despiteeverything,smalltoverysmall.

However,therearedisruptivefactors.Giventhatitproved

notentirelypossibletofullyrandomlyallocatetheconditi-

ons(APStolorry/driver/haulier)andtoblockthesettings

ofthesystems,itcannotbeexcludedthattheeffectsfound

aretheconsequenceofdifferencesamongthevarious

groups.Viceversa,itispossiblethatthedifferencesamong

thegroupsmaskeffectsinthemeasurementsthatare

actuallypresent.Betterinsightintotheseinfluencescanbe

obtainedthroughfurtheranalysesofthedataandverifica-

tionofthehypotheses.

Dutch situationItisalsopossiblethatDutchmotorwaysdifferfromthose

inothercountriesandthatthismaybethecauseofother

effects.TherearethusclearindicationsthatintheNether-

landstheheadwaytimesarerelativelyshortinheavytraffic,

shorterthaninneighbouringcountries.Measurementsof

averageheadwaytimesanddistances(Figure24,chapter

6)revealhowveryclosevehiclesdrivetoeachother.At

80km/htheheadwaytimeinmanycasesislowthan1.5

seconds,andevenlessthan0.5seconds.Atsuchheadway

timestheFCW/HMWgivesacontinuouswarning.

Theseshortheadwaytimescouldhaveaconsiderableeffect

onthedriverintheperformanceofhisdrivingtaskandthe

effectsofsystemsonhowthedrivingtaskisperformed.

ThestrongestindicationcanbefoundintheACCresults,

althoughitisnotknownforwhatperiodoftimetheACC

wasactuallyswitchedon,thebehaviouralchangesfound

weresignificant:6%increaseinaverageheadwaytimeand

3.2%reductioninshort(<1s)headwaytimes,bothgood

forsafety.

LDWAAnoticeablechangeinbehaviouristhatthenumberof

LDWAwarningsfallsbyagood35%whilethisisnotan

intendedACCobjective.Onetheoryisthatkeepingyour

distancefromthevehicleinfront(especiallyifthatisa

lorrythatalsohinderstheviewahead)inbusytrafficisan

intensivedrivertask.ACCtakesthestrainofthatintensive

taskandthusallowsmoreattentiontobepaidtoanother

task:keepingoncourse,resultinginabetterperformanceof

thetask.ThepopularityofACCamongthedriversconfirms

thispicture.

ForLaneDepartureWarningAssist(LDWA)shown

contradictingbehaviouralchanges:thelargedecreaseinthe

numberofwarningsiscoupledwithmoreshortheadways

times,aresultthatalsosuggeststhattheexplanationcanbe

foundinadrivingtaskmodelforthedriver.

AnLDWAsystemthatdistractsfromthemaintaskof

‘queuing’couldcausethiseffect.Itisconceivablethat

adifferentLDWAsettingleadstolessornoincreasein

thedriverloadwherebyanetsafetyeffectisgenerated.

Furthermore,anLDWAcouldserveasasurrogate‘alertness

system’butnoresearchhasbeendoneintothis.

8. Discussion

Final report Accident prevention systems for lorries60

MeasurementsAssumingthatintheDutchsituation,maintainingdistance

totheprecedingvehicleinbusytrafficisakeycomponent

ofthedrivingtask,themeasurementssupportthetheory

that:

• ACCdirectlyalleviatesthemainpartofthedriving

task,withindirectsupportfromFCW/HMW;

• DCandROCactivelypreventdangerouslimitsfrom

beingexceeded;

• LDWAissupportiveinpreventingdangerousdevia-

tionsprovidedtheset-upissuchthattheattentionof

thedriverisnotdistractedfromhismaintask;

• BBFBensuresamoreconsistentdrivingbehaviour

providedthesocialembeddingofthefeedbackis

properlycateredfor.

Astrikingresultisthatjustfive(withjustmaterialdamage)

registeredorreportedduringthemeasuringperiodandall

fivewereinthecontrolgroupwherebythedriverwasnot

informedbutthatdataweremeasured.Forsuchasizeable

populationasinthisfieldoperationaltest(onthebasisof

kilometresdrivenand/ornumberoflorries)anaverageof5

-6accidentsforthereferencegroupand11-13accidents

forthetestgroupwerepredicted.Thereported/registered

numberofaccidentsinthereferencegroupwitha‘silent’

APSwasasexpected.Theabsenceofregisteredorreported

accidentsintheAPStestgroupisastrikingdeviation.This

differencecannotbedirectlyexplainedfromthemeasured

effectoftheAPSorbydifferencesinthequalityofthe

drivers.Sincethereferencegroupwascognisantofthefact

theywereparticipatinginatestusingaccidentprevention

systems,itisunlikelythatthisknowledgewillhavemade

thedifference.Itisrecommendedthatboththegroupusing

APSandthereferencegrouparemonitoredforalonger

periodandtocontinueregisteringthenumberofaccidents

toseewhetherthenumberofaccidentsremainsaslowas

measuredforalongerperiod.

Ithasbeenverydifficulttolayadirectrelationshipbetween

theinfluenceofthesystemsondrivingbehaviourandthe

impactofthisontrafficsafety.Thisismainlybecausethe

driveristheunknownlinkbetweenthe(informing)systems

anddrivingbehaviourinaparticularsituation.Thereap-

pearstobelittlegeneralknowledgeaboutthisrelationship.

Moreover,thedetailedandcontinuousmeasuringofdriving

behaviourfallsoutsidethescopeofthisproject.Insubse-

quentresearchitisrecommendedtodelvedeeperintothe

relationshipbetweenengineeringsystemsandbehaviour,

thatistheperformanceofthedrivingtaskbythedriverin

thecontextofthesurroundingsinordertodevelopbetter

modelsthanarecurrentlyavailable.

TheamountofdatacollectedintheFOTishugeandthe

analysisperformedlimitedgiventheperiodofthetest.Itis

recommendedtomakethedatasetavailabletothirdparties

forfurtheranalysis.

Traffic safetyItisrecommendedtocontinueprovidingincentivestouse

APS,andespeciallyACC,nowthatpositiveexperience

gained.However,giventheadverseeconomiccircum-

stancesinthetransportsector,thewillingnesstoinvestis

currentlylow.

Thetotalnumberoflorriesinvolvedwasaround2,400from

123participatingcompanies,whichmadethisamuchlarger

andmoreextensivefieldoperationaltestthanprevious

testsofAPSequipment.Thisfactgeneratedbothchallen-

gesandlimitationsaswellaslearningexperiencesabout

tacklingsuchlarge-scalepracticaltrialsanddataprocessing.

Learningexperiencesthatarequiteunique,giventhelevel

of(international)interest.

8. Discussion

Final report Accident prevention systems for lorries 6�

Effectiveness of the systems on the test track Thetesttrackexperimentsandloantestrevealthetechnical

effectivenessofactivedriversupportsystems(intervention,

informationandfeedback).Theydowhattheyhavetodo:

reliablydetect,warnand,wherepossible,intervene.They

appeartobeadequatelyrobustandreliableforuseinthe

dailyoperationsofahaulier.

Effectiveness of the systems in practiceTheresultsoftheanalysesindicatethatthesystemshavean

effectonthedrivingbehaviourofthedriver.

ACC WhileitisnotknownforwhatperiodoftimetheACCwas

actuallyswitchedon,thebehaviouralchangesfoundwere

significant:6%increaseinaverageheadwaytimeand3.2%

reductioninshort(<1s)headwaytimes,bothgoodfor

safety.

DC/ROCTheeffectofDCandROConrolloverriskisclearlyfound

intheloantest.Giventhatthesesystemsinterveneauto-

nomously,thecertaintythattheywillhaveaneffectis

considerable.

LDWATheresultsoftheLDWAsystemrevealafallof30%(retrofit)

to60%(‘ex-factory’)ofthenumberofLDwarnings.Inboth

casesthereductionispositive,wherebyitisnoticeable,to

saytheleast,thatforretrofitalowereffectisfoundthanfor

ACC(35%fewerLDwarnings).Thedifferencescouldbe

attributabletotheresearchgrouportheset-upanduseof

LDWA(theex-factorysystemsare,forinstance,adjustedby

thesupplieraccordingtoitsstandardset-up.)Thesimulta-

neousincreaseof5.9%inshortheadwaytimes(<1%)found

inthegroup‘ex-factory’(thecategorywherethebiggest

effectisfoundonLDwarnings-60%)isunfavourable.

FCW/HMW ThevarianceanalysisintotheeffectofHMWandFCWon

thepercentageofshortheadwaysrevealsnosignificant

differencewhiletheanalysisoftheaveragetrafficflow

headwaytimesforaspecificgroupshowanincreaseinthe

headwaytimesofaround0.14seconds.

BBFBOneBBFBtypewasusedinthetestwherebythebehaviou-

raleffectvariedfordifferentgroups,namelyahaulieranda

groupofrentedlorries.Thefirstgroupshowedthedesired

behaviour,24%lessspeedvariation,whilethesecond

groupshowedslightlyundesirablebehaviour,5%more

speedvariation.

AccidentsTherewere5accidents(withjustmaterialdamage)registe-

redorreportedduringthemeasuringperiodandall5were

inthecontrolgroupwherebythedriverwasnotassistedby

anAPS.Forsuchasizeablepopulationasinthisfieldopera-

tionaltest(onthebasisofkilometresdrivenand/ornumber

oflorries)anaverageof5-6accidentsforthereference

groupand11-13accidentsforthetestgroupwerepre-

dicted.Thereported/registerednumberofaccidentsinthe

referencegroupwithoutAPSwasasexpected.Theabsence

ofregisteredorreportedaccidentsintheAPStestgroupisa

strikingdeviation.

9. Conclusions

Final report Accident prevention systems for lorries6�

Effects on traffic safetyAmodelhasbeenestablishedtoenableestimatestobe

madeofactiveinterveningsystemsandtheseshowthat

ACCandDC/ROCmaybeexpectedtohavealargerimpact

thanothersystems.

ItisclearthatDC/ROChasaneffectonsafety.Theeffect

ofSWOV[26]canbecalculatedas1preventedfatalityand

5preventedhospitalcasualtiesannually.Forallthevictims

towhomtheAPStestrelates,some25fatalitiesand135

hospitalcasualtiescausedbyaccidentsinvolvinglorrieson

motorways,thisis4%.

ItcanbeassumedthatAdaptiveCruiseControl(ACC)

willreducetheincidenceofvictimscausedbyaccidents

involvinglorriesonmotorways.Sincerear-endcollisions(1st

collidingvehiclebeinglorry)andsingularaccidentsmakeup

asubstantialproportionofseriousaccidents,ACCcanhave

aconsiderableeffect.

Althoughthemeasurementsdonotprovideanunambi-

guouspicture,itcanbeassumedthatthattheapplicationof

HMW/FCWwillleadtoapositiveeffectonrear-end

collisionsandsingularaccidents.

ThesameappliestoBBFBifitisincorporatedproperly

withinsocialbehaviourinfluences.

Effects on traffic flowTheeffectofAPSonthetrafficflowwaspredictedusing

aconceptualtrafficflowmodelcomposedonthebasisof

literatureandexpertmeetings.Thedirecteffectontraffic

flowisminorsincehardlyanysignificantdeviationsofthe

averagespeedandheadwaytimecouldbedemonstrated

betweenvehiclescontainingactiveAPSandthereference

group.Theindirecteffectbyavoidingaccidentswillbe

present,however,butisdifficulttoquantify.Themagni-

tudewillalwaysbelimitedgiventheverymodestshare

(ca.1.6%)ofthelostvehiclehourscausedbyaccidents

involvinglorries[15].

Stimulating useConsultationamongplayersinthemarketanddriver

questionnairesrevealthatthesesystemsarevaluedbythem

inpractice,providedthattheyaresetupinharmonywith

practice(preventionofexcessivewarning).Thesystems

contributepositivelytotheperceptionofsafedrivingand

theprofessionalismoftheperformancebythedriverof

hisdrivingtask.ACCisparticularlyexperiencedaspositive

andtherobustnessofallsystemsconsideredmorethan

adequate.

FollowingthepracticaltestthenumberofAPSsystems(dif-

ferentfromROC/DC)comingontothemarket(ca1,600)

hasrisenconsiderably.Thesystemsarenotbeingextended

butbroughtbacktotheiroriginalstateandgiventothe

hauliersthatcollaborated.Virtuallyalltheparticipating

companieshaveindicatedadesiretocontinueusingthese

systemsaftertheendofthetest.Atleast7companieshave

indicatedthattheywillextenduseofAPStolorriesnot

currentlyequippedwiththesystem.

Thereststillwanttohavemoreinsightintothecosts-

benefitsanalysisofthesesystems.

9. Conclusions

Final report Accident prevention systems for lorries 63

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Final report Accident prevention systems for lorries64

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2009C298.Pauwelussen,2009.

[20]VerificationoftheeventsintheOCTOdatabasefor

threevehicles,R.M.T.Wouters,2009.

[21]APSProject-DataQualityAssessment,

FinalReport,Ernst&Young,July2009.

[22]APSdriverquestionnaire,opinionsofthedrivers

involvedofaccidentpreventionsystems,

AnjaLangefeld,June2009.

[23]Accidentpreventionsystemsonlorries,

resultsofinterviewsessions,BCI,June2009,Nijmegen.

[24]APScompanyprofile,profilesofparticipating

companies,AnjaLangefeld,June2009.

[25]Reportsofbusinessowners’meetingsAPS,

DelftandNijmegen,June2009.

[26]Trafficsafetyeffectsofaccidentpreventionsystem,

RobEenink,July2009.

[27]Accidentpreventionsystemsforlorries,

selectionprocedure,BCI,March2009,Nijmegen.

[28]Thesafetyoflorries,Kampen,vanL.T.B,

Schoon,C.C.,SWOV,R-99-31,Leidschendam1999.

[29]SWOVFactsheet-Lorriesanddeliveryvans,SWOV,

LeidschendamJanuary2008.

[30]Accidentpreventionsystemsforlorries,

APSinafieldstudy,VanSchijndel-deNooij,

M.,Jansen,S.,Driever,H.,VandeWiel,B.,Ruijs,

P.,Huijskes,C.,Landman,R.,Schrijver,J.,VanLange,

F.,Hoedemaeker,M.,Yu,X.,&DeRee,D.TNO2008.

(TNOreportTNO-033-HM-2008-00045).Helmond:

TNOScienceandIndustry.

[31]Kuiken,M.,Overkamp,D.,&Fokkema,J.(2006).

Accidentswithlorriesonnationaltrunkroads:

Frequency,causes,consequencesandsolutions

(endreport).DHV/Rijkswaterstaat-

AdviesdienstVerkeerenVervoer.

Supplementary reports ThereportsbelowformaseparatepartofthisAPSreport:

[21}APSProject-DataQualityAssessment,FinalReport,

Ernst&Young,July2009.

[26]Trafficsafetyeffectsofaccidentpreventionsystems,

RobEenink,SWOV,July2009.

Literature

Final report Accident prevention systems for lorries 65

ACC

Adaptive Cruise Control

Thissystemusessensorstoautomaticallymaintainasafe

distancetothevehicleinfrontandtomaintainaspeedset

bythedriver.Ifnecessary,itadaptsthespeedofthevehicle

tomaintainsufficientheadwaydistance.

Anti-rollover tests

ThetestingoftheeffectsoftheDirectionalControlandRol-

loverControlanti-rolloversystemsduringextremesteering

movements.Thisoccurredonatesttrackwiththeaidofa

lorryfittedwithside-wheels.Subsequently,measuringdata

abouttherolloverriskwascollectedonthepublichighways.

APS

Accident prevention systems

Driverassistancesystem.

APS Detail

DuringeachAPSeventafragmentvan10sdataislogged

indetail.Thisincludesdateandtime,GPSlocation(1Hz),

acceleration(inbothlongitudinalandlateraldirections;10

Hz),signalsfromtheCliffordElectronics/MobilEye(approx.

10Hz).Themaximumlimitsetonthequantityofthistype

ofdatacollectedpermonthperlorrywas6Mbinconnec-

tionwiththeGPRScosts.

APS Summary

Detailedinformationeachtimethatanoutputsignalfrom

anAPSchangesstatus,thiscountsasaneventthatwillbe

logged.Thefollowingarelogged:date,time,licenceplate

number,eventtype,currentspeed,GPSlocation,mapmat-

chingoutput.Aneventisloggedonlyatspeedsexceeding

55km/handonlyintheNetherlands.

BBFB

Black Box Feed Back

Thisregistrationsystemmeasuresthedriver’sbehaviour

duringdrivingandrecords,forexample,fuelconsumption,

speed,brakemovementsandtheuseofcruisecontrol.The

systemfeedsthesedatabacktothedriver.

Bulk

Goodstradedbasedonweightand/orcontent.

Conceptual model

Thismodelindicatesthescopeoftheresearchelement,the

selectionofthecharacteristics(variables),andtherelation-

shipsbetweenthesecharacteristics.Inordertomeasurethe

effectsondrivingbehaviour,safetyandtrafficflowinthe

test,conceptualmodelsweredevelopedthatcouldtranslate

theoutcomesoftheanalysisintotherequestedeffects.

Crash Detail

Detailedinformationofeachcollision;inafragmentof7s:

dateandtime,GPSposition(1Hz),accelerationinlongitu-

dinalandverticaldirections(100Hz).

Crash Summary

Summaryinformationofeachsuspectedcollision;dateand

time,licenceplatenumber,GPSlocation,maximumaccele-

ration,collisionspeed.

DC

Directional Control

Asystemabletocorrectover-andunder-steeringproblems.

Thissystemcontrolsthebrakeswhenthesteeringmove-

mentdeviatestoomuchfromthevehicledirection.

Driver group

Thissubprojectlookedprimarilyatdrivingbehaviour.This

involvedusingdatafromtheblackboxandinterviewswith

Appendix �: Explanatory word list

Final report Accident prevention systems for lorries66

drivers.Thissubprojectwascarriedoutonalargescale

amongalimitednumberofcompanies.

eIMPACT

eIMPACTisaprojectinthesixthEUframeworkprogramme

for‘InformationSocietyTechnologiesandMedia’.Itanaly-

sedthesocio-economicconsequencesofIntelligentVehicle

SafetySystems.

ESC

Electronic Stability Control

ESP

Electronic Stability Program

Built-inactivesafetyelementtostabilisethevehicle.

Estimation algorithm

Acalculationmethodologythatcalculatesanestimatefora

certainparameter.

Factory-fit systems

Systemsbuiltintonewlorriesbythemanufacturer.

FCW/HMW

Forward Collision Warning/Headway Monitoring and Warning

Thesesystems,whichinthisstudywerelinked,warnthe

driverwhenthelorryapproachesanotherobjecttooclosely;

theaimistopreventacollision.Atthemomentthattheve-

hiclekeepsinsufficientdistance,thesystemgivesanaudio

andvisualsignalviaadashboarddisplay.

FESTA

EuropeanCommissionprojectinwhichamethodwas

devisedfortheperformanceoflarge-scalefieldtests.This

projectresultedinguidelinesfortheset-up,performance,

andanalysisoflarge-scalefieldtests.TheseFESTAguideli-

neswereadheredtointheAPStest.

FOT

Field Operational Testorfieldtest

General cargo

Allsortsofharmless,conventionalgoods,suchasdomestic

items,electronicsandplastics.Usuallypackedonpalletsor

incontainers.

GPRS

General Packet Radio Service

Standardfordatatransmission

GPS

Global Positioning System

Locationdeterminationusingasatellitesystem

GSM

Global System for Mobile communication

Adesignationforastandardfordigitalmobiletelephony.

ITS

Intelligent Transport Systems and Services

LDWA

Lane Departure Warning Assist

Thissystemwarnswhenthevehicleisabouttoleavethe

lane.Acamerarecognisesthedifferencebetweentheroad

surfaceandthelinesandissuesawarningatthemoment

thatthevehicleisabouttocrossaline;nouseoftheindica-

torisinvolved.

Appendix �: Explanatory word list

Final report Accident prevention systems for lorries 67

MAUT

LKW-Maut,route-dependenttollforlorriesinGermany.

Mobileye

Brandnamefortheretrofitin-builtaccidentprevention

systems.

OEM group

Inconsultationwithvariousmanufacturers,severalsystems

werefactory-fittedinlorriesandthentracked.

OEMs

Original Equipment Manufacturers

Thisreferstothemanufacturersofcarsandlorries.

Operational driving behaviour

Thisreferstotheelementarydrivingtasksthatmustbe

carriedouttodriveavehicle,suchasoperatingthepedals,

changinggearandsteering.Together,theseelementary

tasksformamanoeuvre.

Predictive algorithm

Acalculationmethodologythatmakesapredictionabout

thevalueofacertainparameterinthefuture.

Reference group

Agroupofvehiclesequippedwithaccidentprevention

systemsthatissuenowarningbutonlymeasure;thiswas

donetoenablethemeasurementofthedifferencewiththe

systemsthatissuedawarning.

Retrofit group

Inthissubprojectaccidentpreventionsystemswerebuilt

intothelorriesandtestedovereightormoremonths.

Retrofit systems

Systemsbuiltintolorriessometimeaftertheyhaveleftthe

manufacturer.

Request for Quotation

Invitationtosupplierstosubmitabidforproductsor

services.

ROC

Roll Over Control

Systemthatcounteractsthevehicle’sinclinationtorollover.

RPAS

Roll over Propensity Assessment System

Sensorsandanalgorithmcoupledtothemwithwhicha

vehicle’srolloverlimitisdetermined.

Silent APS

Accidentpreventionsystemthatonlymeasures;itissuesno

warningtothedriver.

Strategic driving behaviour

Theaimsofatriparedeterminedatthestrategiclevelof

drivingbehaviour,forexample,whereto,howandhow

long.Decisionsatthestrategiclevelareinfluencedbycosts

andrisks,aswellasbyattitudesandtheavailableinforma-

tion.

Tactical driving behaviour

Tacticaldrivingbehaviourreferstothemanoeuvresperfor-

medbydrivers,suchasovertakingandcrossingajunction.

Duringtacticaldrivingbehaviourthedriverisprimarily

concernedwiththeinteractionwithothertrafficand/or

withtheroad.Tacticaldrivingbehaviourisdetermined,on

theonehand,bythecurrentsituationand,ontheother,by

theaimssetatthestrategicdrivingbehaviourlevel.

Appendix �: Explanatory word list

Final report Accident prevention systems for lorries68

TLC

Time to Line Crossing

Thetimeremaininguntilthevehicletouchesthelane

markings,providedcourseandspeedremainunchanged.

Trigger level

Thelevelatwhichaparameterexceedsorfallsbelowa

predeterminedvalue.

Trip Detail

Moredetailedinformationofeachtrip;each2km,dateand

time,theGPSposition,mapmatchingoutput(roadtype,

speedlimit),averagespeedoverthe2kmcovered,current

speed,currentheadwaytime.

Trip Summary

Summarystandardinformationofeachtrip;dateandtime

ofstartandfinishofthetrip,distancecovered,average

speedovertheentiretrip,maximumspeedovertheentire

trip.

TTC

Time To Collision

Thetimeremainingbeforeacollisionbetweentworoad

users,providedcourseandspeedremainunchanged.

Variance analysis

Thisisastatisticalcheckingprocedureusedtofindout

whetherthepopulationaveragesoftwoormoregroups

differsignificantlyfromoneanother.

Appendix �: Explanatory word list

Final report Accident prevention systems for lorries 69

Appendix �: List of hypotheses

DATA SOURCE Point data APS Summary APS Detail Crash data BBFB-data Outcome

0 General (to test for all APS groups) ---

0.1a BBFBhasnoeffectontheaveragespeed x VBBFB=85.4km/hVREF=85.8km/h

[p<0.05]

0.2a BBFBhasnoeffectonthedistribution(s.d.)ofthespeed x STDVBBFB=1.68km/hSTDVREF=1.78km/h

[p<0.001]

0.3a BBFBhasnoeffectonhowoftenharshbrakingoccurs x Notsignificant

0.1b FCW/HMWhasnoeffectontheaveragespeed x Notsignificant

0.2b FCW/HMWhasnoeffectonthedistribution(s.d.)ofthespeed x Notsignificant

0.3b FCW/HMWhasnoeffectonhowoftenharshbrakingoccurs (x) (x) Nottestable(NOTE1)

0.4b FCW/HMWhasnoeffectontheaverageheadwaytime x Notsignificant

0.5b FCW/HMWhasnoeffectonthenumberoflanechanges(perkm) X Nottestable(NOTE2)

0.1c LDWAhasnoeffectontheaveragespeed x SP1:N.S.SP3a:N.S.SP3b:N.S.

0.2c LDWAhasnoeffectonthedistribution(s.d.)ofthespeed x SP1:N.S.SP3a:N.S.SP3b:N.S.

0.3c LDWAhasnoeffectonhowoftenharshbrakingoccurs (x) (x) Nottestable(NOTE1)

0.4c LDWAhasnoeffectontheaverageheadwaytime x SP1:N.S.SP3a:N.S.SP3b:N.S.

0.5c LDWAhasnoeffectonthenumberoflanechanges(perkm) X Nottestable(NOTE2)

0.1d ACChasnoeffectontheaveragespeed x Notsignificant

0.2d ACChasnoeffectonthedistribution(s.d.)ofthespeed x Notsignificant

0.3d ACChasnoeffectonhowoftenharshbrakingoccurs (x) (x) Nottestable(NOTE1)

Final report Accident prevention systems for lorries70

Appendix �: List of hypotheses

DATA SOURCE Point data APS Summary APS Detail Crash data BBFB-data Outcome

0 General (to test for all APS groups) ---

0.4d ACChasnoeffectontheaverageheadwaytime x 1.68sref;1.77sACC[p<0.05}

0.5d ACChasnoeffectonthenumberoflanechanges(perkm) X Nottestable(NOTE2)

0.1e ROChasnoeffectontheaveragespeed x 81.3km/href;80.4km/hROC[p<0.01]

0.2e ROChasnoeffectonthedistribution(s.d.)ofthespeed x 4.5km/href;3.9km/hDC[p<0.01]

0.3e ROChasnoeffectonhowoftenharshbrakingoccurs (x) (x) Nottestable(NOTE1)

0.4e ROChasnoeffectontheaverageheadwaytime x N.S.

0.5e ROChasnoeffectonthenumberoflanechanges(perkm) X Nottestable(NOTE2)

� Via BBFB, the use of black box systems will improve better driving behaviour ---

1.1 WithBBFBtherearefewerspeedvariations x Notsignificant

1.2 WithBBFBharshbrakingoccurslessoften x Notsignificant

1.3 WithBBFBcruisecontrolisusedmorefrequently x Notsignificant

1.4 WithBBFBthefuelconsumptionislower x Notsignificant

� FCW/HMW reduces the number and severity of accidents ---

2.1 WithFCW/HMWthenumberofaccidents(per1000km)islower x Nottestable(NOTE3)

2.2 Intheeventofacollision,themaximumdecelerationislowerwithFCW/HMW x Nottestable(NOTE3)

2.3 Intheeventofacollision,thecollisionspeedislowerwithFCW/HMW x Nottestable(NOTE3)

3 FCW/HMW reduces the number of almost-accidents ---

3.1 WithFCW/HMWlessfrequentshortheadwaytimes(<1s) x N.S.

3.2 WithFCW/HMWlessfrequentlowTTCs (x) Tobecompleted

3.3 AfteranFCW/HMWwarning:higherminimumheadwaytime X Notsignificant

Final report Accident prevention systems for lorries 7�

Appendix �: List of hypotheses

DATA SOURCE Point data APS Summary APS Detail Crash data BBFB-data Outcome

3 FCW/HMW reduces the number of almost-accidents ---

3.4 AfteranFCW/HMWwarning:higherminimumTTC X Tobecompleted

3.5 WithFCW/HMWlessfrequentshortheadwaydistances(MobileyeHMWisred) x X Notsignificant

4 LDWA reduces the number and severity of the accidents ---

4.1 WithLDWAthenumberofaccidents(per1000km)islower x Nottestable(NOTE3)

4.2 Intheeventofacollision,themaximumdecelerationislowerwithLDWA x Nottestable(NOTE3)

4.3 Intheeventofacollision,thecollisionspeedislowerwithLDWA x Nottestable(NOTE3)

5 LDWA reduces the number of almost-accidents ---

5.1 WithLDWAlessfrequentunintentionallinecrossings x SP1:16.3/uref;11.1/uLDWA[p<0.001]

SP3a:notsignificantSP3b:13.0/uref;5.0/u

LDWA[p<0.001]

5.2 AfteraLDWAwarning:largermarginsre.theroadlines(definitionofsign:+stayswithinlines,-islinecrossing)

X SP1:-0.25mref;-0.23mLDWA[p<0.05];SP3a:notsignificantSP3b:notsignificant

5.3 AfteraLDWAwarning:lesslinecrossing X Wastestedwith5.2

6 ACC reduces the number and severity of the accidents ---

6.1 WithACCthenumberofaccidents(per1000km)islower x Nottestable(NOTE3)

6.2 Intheeventofacollision,themaximumdecelerationislowerwithACC x Nottestable(NOTE3)

6.3 Intheeventofacollision,thecollisionspeedislowerwithACC x Nottestable(NOTE3)

7 ACC reduces the number of almost-accidents ---

7.1 WithACClessfrequentshortheadwaytimes(<1s) x 12.6%Ref;9.4%ACC[p<0.01]

7.2 WithACClessfrequentlowTTCs (x) N.S.

Final report Accident prevention systems for lorries7�

Thedatasourceusedforthetestingofahypothesisis

indicatedbyan‘x’.‘(x)’isusedtosignifythatalthoughdata

wasavailablewithwhichtotestthehypothesis,therewas

lessofitthanwasdesirable.

Wherecomparisonsaremadeinthehypotheses(‘with

APSfeweraccidents’),thisalwaysmeans‘comparedtothe

situationwithoutAPS’,inotherwordscomparedtothe

referencegroup.

Inthelistofhypothesesnoformalnullhypothesisand

alternativehypothesisarementioned.Wherenoclear

expectationsexistedatthestart,weexpressthezero

hypothesis(‘noeffectofAPS’).If,however,aclearexpec-

tationexistedforaspecificvariableforaspecificAPS,we

mentionthealternativehypothesis(‘withLDWAfewer

unintentionallinecrossings’).

Note �

Itturnedoutthataccelerationhadnotbeensavedcorrectly

inthedatainSP1andSP3.Asaresult,itwasnotpossible

toanalyseharshbraking.

Note �

LanechangessuchasthoseestablishedbyCliffordElectro-

nics/MobileyeweremarkedintheOctoTelematicsdata.

However,thisappliesonlytothe10sfragmentsloggedin

relationtoevents.Asaresult,ageneralanalysisofthelane

changebehaviourwasnotpossible.Asanalternative,the

numberoflanechangesintheeventswasanalysed.

Note 3

ThisanalysisdrewontheCrashSummaryandCrashDetail

files.Intotal81,066possiblecollisionsoccurred,allwithan

acceleration/decelerationofatleast2g.Actualcollisions

couldnotbeeasilyselectedfromthisgroup.

Appendix �: List of hypotheses

DATA SOURCE Point data APS Summary APS Detail Crash data BBFB-data Outcome

8 ROC (anti-rollover system) reduces the number and severity of the accidents

---

8.1 WithROCthenumberofaccidents(per1000km)islower x Nottestable(NOTE3)

8.2 Intheeventofacollision,themaximumdecelerationislowerwithROC x Nottestable(NOTE3)

8.3 Intheeventofacollision,thecollisionspeedislowerwithROC x Nottestable(NOTE3)

9 DC reduces the number and severity of the accidents ---

9.1 WithDCthenumberofaccidents(per1000km)islower x Nottestable(NOTE3)

9.2 Intheeventofacollision,themaximumdecelerationislowerwithDC x Nottestable(NOTE3)

9.3 Intheeventofacollision,thecollisionspeedislowerwithDC x Nottestable(NOTE3)

Final report Accident prevention systems for lorries 73

Thefiguresbelowareenlargementsofthediagramspresen-

tedinchapter6.2(conceptualmodeloftrafficflow).

Inthefigureabove(exclusivelylorries)arelationship

betweentheheadwaytimeandspeedoflorriesissought

basedontheactualdata.Fromthisrelationship,themini-

mumheadwaytimecanbederivedandthenlanecapacity

estimatedforthehypotheticalsituationoftrafficcomprising

exclusivelylorriesequippedwithAPS.

Thefigurebelow(mixedtraffic,i.e.,equippedandnon-

equippedlorriesandothertraffic)presentsafundamental

diagramforthereferencesituationonthebasisofdatafrom

measuringloops.Fortheprojectsituationthedatapoints

weremodifiedbasedonthetestdata.Eachdatapointin

thereferencesituationisthusshiftedandanewdiagram

created.Thecapacityisthemaximumintensityaccordingto

thisdiagram.

Appendix 3: Figures showing conceptual models of traffic flow

Fundamental diagram method,mixed traffic

intensity

spee

d

- equipped- non-equipped

Fundamental diagram method, freight traffic only

head

way

tim

e

speed

- equipped- non-equipped

change in capacity

trafficcapacity

traffic without system

traffic with system

change in capacity

Fundamental diagram method,mixed traffic

intensity

spee

d

- equipped- non-equipped

Fundamental diagram method, freight traffic only

head

way

tim

e

speed

- equipped- non-equipped

change in capacity

trafficcapacity

traffic without system

traffic with system

change in capacity

Final report Accident prevention systems for lorries74

Programme Consultative Board

L.Molenkamp,M.deMos,M.Bogaerts,

FileProofProjectOrganisation

R.L.Verweij,MinistryofTransport,PublicWorksandWater

Management

N.Anten,A.W.vanHattum,Connekt/ITSNetherlands

Core Team

R.L.Verweij,MinistryofTransport,PublicWorksandWater

Management

A.W.vanHattumandP.T.Potters,Connekt/ITSNetherlands

A.A.W.deRuiter,J.H.HogemaandC.J.Ruijgrok,TNO

M.W.G.MichonandJ.H.Smeenk,BuckConsultants

International

Advisory Group

J.vandeBraak,RAIAssociation

O.E.B.Hamel,BOVAG

K.deWaardt,VERN

J.S.Boonstra,R.Aarse,TLN

P.J.C.Teulings,EVO

A.deHaes,KNV

Scientific Sounding Board

T.P.Alkim,MinistryofTransport,PublicWorksandWater

Management

H.E.Wagter,Askary

B.vanArem,TUDelft

F.C.M.Wegman,SWOV

G.P.vanWee,TUDelft

M.deMos,R.vanHout,FileProofProjectOrganisation

Communication Group

R.LeytenandA.Klaver,FileProofProjectOrganisation

E.deWaard,Connekt/ITSNetherlands

B.vanBreeandS.Slütter,BuckConsultantsInternational

Appendix 4: Organisation

Final report Accident prevention systems for lorries 75

InthesubprojectsRetrofit(SP1)andOEM(SP3)data

registrationtookplaceusingregistrationunitsproducedby

CliffordElectronics/MobileyeandOctoTelematics.These

unitswerebasedonthe‘ClearBox’conceptdeveloped

byCliffordElectronicsandOctoTelematicsandaMobil-

eye.WiththeaidofaGPRSconnection,aGPSantenna,

anaccelerationsensorandaCANbuslinkwiththeAPS

(Mobileye:LDWA,FCW/HMW)threetypesofdatawere

collected(see[2,3]fordetailedspecifications).

ThesedatawereenhancedbyOctoTelematicswithGIS

data(convertedtogeo-codesforroads),filteredwhere

necessary,andclusteredtoformanumberofdatafiles.

TRIP_SUMMARY,summarystandardinformationofeach

trip;dateandtimeofstartandfinishofthetrip,distance

covered,averagespeedovertheentiretrip,maximum

speedovertheentiretrip.

TRIP_DETAIL,detailedinformationofeachtrip;each2km,

dateandtime,theGPSposition,mapmatchingoutput

(roadtype,speedlimit),averagespeedoverthe2km

covered,currentspeed,andcurrentheadwaytime.

APS_SUMMARY,detailedinformationduringanevent;

eachtimethatanoutputsignalfromanAPSchangesstatus,

thiscountsasaneventthatwillbelogged.Thefollowing

arelogged:date,time,licenceplatenumber,eventtype,

currentspeed,GPSlocation,andmap-matchingoutput.An

eventisloggedonlyatspeedsexceeding55km/handonly

intheNetherlands.

APS_DETAIL,duringeachAPSeventafragmentvan10s

dataisloggedindetail.Thisincludesdateandtime,GPS

location(1Hz),acceleration(inbothlongitudinaland

lateraldirections;10Hz),signalsfromtheCliffordElectro-

nics/Mobileyeunit(approx.10Hz).Themaximumlimit

setonthequantityofthistypeofdatacollectedperweek

foreachlorrywas1.25MByteorapprox250APSDetail

measurements.Inordertominimisethebiasintroducedby

thislimitation,thestartmomentforthecollectionofthese

dataperlorrywaschosenafresheachweek.Theconcluding

momenteachweekwasthendeterminedbythenumberof

eventsgeneratedbythelorryinquestion.

CRASH_SUMMARY,summaryinformationofeachpossible

collisionissaved(definition:ameasuredaccelerationin

longitudinalorlateraldirection>40m/s2);dateandtime,

licenceplatenumber,GPSlocation,maximumacceleration,

andcollisionspeed.

CRASH_DETAIL,detailedinformationofeachpossiblecol-

lision;inafragmentvan7s:dateandtime,GPSposition(1

Hz),accelerationinbothlongitudinalandverticaldirections

(100Hz).

Followingthefirstanalysisoftheoutcomeofthedataregi-

stration,varioussettingsandfilterswereappliedtoimprove

thequalityofthedataand/ortoreducethenumberof

recordswithuselessinformation:

• Raisingthetriggerlevelforaccelerationsfrom2Gto

4G(20to40m/s2).

- Theshockstowhichalorrychassisissubjectare

muchstrongerthanthoseaffectingacar.In

normaluse,thelimitof2Gisveryoftenexceeded

asaresultofwhichverymanycrashdetailrecords

withoutanyvaluearegenerated.

Appendix 5: Analysis of measurements taken during field operational test

Final report Accident prevention systems for lorries76

• FortheHeadwayMonitoringandWarning,a5-second

delaywasbuiltinconcerningthevehicle’sresumption

ofapreviouslevel,i.e.whenthedistancetothevehicle

infrontincreasedandthenresumedthewarninglevel.

Itwasevidentthatwithoutthisdelayverymany

recordswithoutadditionalinformationweregenerated

attheboundarybetweentwolevels.

• Theblinkinglighthadtoceaseblinkingforatleast2.5

secondsbeforeitsusecouldtriggeranewevent.

TheacquisitionsystemforSP2differedfromalltheothers

becauseitwasgeneratedusingthefleetmanagement

systemproducedbyCarrierWeb.

Thefrequencywithwhichthedataweresavedwasonce

everytwominutes.Nocurrentvaluesweresavedbutrather

indicators,whichwerecalculatedimmediately,concerning

theelapsedperiodof2minutes,forexampletheaverage

speedandthemaximumacceleration/deceleration.See

Table15foralistofthesaveddata.

Therawdatafromthedataregistrationwerequalitycon-

trolledpriortoprocessingandfilteredagain,ifnecessary.

Duringsub-analysessubsetswereenhancedwithvariables

ofimportancetotheanalysis,suchasthefilesofactualdata

basedonthemeasuredGPSpositions,roadtype,numberof

lanes,applicablespeedlimits,etc.

Withtheconversionandtheadditionofindexationdata,

thefilesthatwereanalysedbecamelargerthantheoriginal

datafiles.

Table16showsthequantityofrawdatacollectedinSP1

andSP3.Thetotalismorethan170GigaBytes.

Appendix 5: Analysis of measurements taken during field operational test

Chart 15: Data collected in SP2 Chart 16: Amount of SP1 and SP3 data collected

Variable Note

CWVehicleID Licencenumber

EventTime Dateandtime

SpeedMin

SpeedMax

SpeedMean

SpeedStdDev

AccelerationMin

AccelerationMax

AccelerationMean

AccelerationStdDev

DecelerationMin

DecelerationMax

DecelerationMean

DecelerationStdDev

ActualFuel

TotalKM

TotalCruiseTime Timecruisecontrolwason

TotalBrakeApps Numberofbrakeevents

TotalTimeOverspeed

HarshAccelerations Numberoftimesrapidacceleration(a>1.0m/s^2)

HarshBrakes Numberoftimesrapidacceleration(a>1.5m/s^2)

Data file Data Space (Mb)

TRIP_SUMMARY 71

TRIP_DETAIL 49.372

APS_SUMMARY 19.678

APS_DETAIL 103.072

CRASH_SUMMARY 11

CRASH_DETAIL 361

Totaal �7�.860

Final report Accident prevention systems for lorries 77

Table17showsthenumberofkilometresdriventhatwas

loggedpermonthinSP1andSP3.Thenumberoflorries

wasdeterminedeachmonthbyarangeoffactors,including

theavailabilityofunitsandtherepairandmodificationof

APSanddataregistration.

Table18showsthequantityofrawdatacollectedinSP2.

Thetotalismorethan14GigaBytes.

Table19showsthenumberofkilometresdrivenand

measuredinSP2.

Thenumberoflorrieswasdeterminedeachmonthbya

rangeoffactors,includingtheavailabilityofunitsdelivered

factory-fittedandtherepairandmodificationofAPSand

dataregistration.

Appendix 5: Analysis of measurements taken during field operational test

Chart 17: Kilometres driven and measured in SP1 and SP3

Chart 18: Amount of data collected in SP2

Chart 19: Kilometres driven and measured in SP2

Year Month Total km driven Total journeys Average kilometres per day Number of lorries

2008 10 8.145.428 248.417 345 1.043

2008 11 8.173.006 248.136 333 1.223

2008 12 8.818.063 254.757 333 1.304

2009 1 9.259.496 264.454 328 1.350

2009 2 9.203.939 276.281 322 1.469

2009 3 10.800.269 330.630 323 1.493

2009 4 10.218.884 311.555 326 1.498

2009 5 9.033.672 278.108 310 1.547

Total 73.65�.757 �.���.338

Data file Data Space (Mb)

Haulier1_data 400

Haulier1_GPSdata 1.200

Haulier2_data 2.400

Haulier2_GPSdata 10.300

Total �4.300

Year Month Total km driven

Number of lorries

Haulier �

3 101.459 51

4 227.330 51

5 253.975 86

Subtotal 58�.764

Haulier �

2009 2 50.082 71

2009 3 698.452 405

2009 4 800.042 455

2009 5 920.263 453

Subtotal �.468.839

Total 3.05�.603

Final report Accident prevention systems for lorries78

Measurements

Owingtothelengthymeasuringperiod,particularlyinSP1

andSP3,allsortsofweatherconditionswereencountered,

fromextremecoldinthewinter(to-20°C)toheatinthe

spring(30°C),dryweather,wetweatherandsnow.Data

thatwasinfluencedbyextremeweather,suchasthesnow

inJanuary2009thatwasextremebyDutchstandards,have

notbeenincludedintheanalysis.

ThehypothesespresentedinAppendix2weretestedinthe

dataanalysis.Thisinvolvedtheuseofvarianceanalysis.The

analysiswasperformedondatacollectedonDutchmotor-

ways.Theindependentvariableswere:

• APS(withtheconditionsLDWA,FCW/HMWand

referenceservingasexamplesinSP1).

• Thespeedlimit,with120,100andoccasionally

80km/haspossiblevalues.Thisvariablewascorre-

latedwiththelocationwherethelorrydrove.Thelimit

of100km/hisfoundtypicallynearurbanareasanda

speedlimitof80km/happliedatacoupleofspecific

locations.

• Half-day,withdayandnightaspossiblevalues.

Thisvariableincludestheeffectsofbothlightconditions

andweightoftraffic.

Bywayofexample,theanalysisresultsforSP1foraverage

speedarediscussedhere.Varianceanalysisrevealedthe

followingeffects.

• Thespeedlimithasastatisticallysignificanteffect

[p<0.001].AsFigure32shows,thefollowingistrue:

thehigherthespeedlimit,thehighertheaverage

speed.

• Thehalf-dayhasasignificanteffect[p<0.001].

Averagespeedatnightissomewhathigherthanduring

thedaytime(81.1and80.8km/hrespectively:a

differenceof0.3km/h).

• APShasnosignificanteffect[p=0.76].Thus,the

averagespeedwasnotinfluencedbyAPS.

VisualssuchasthoseshowninFigure32showtheaverage

valuesfoundbymeansofasmallblockorasimilarsymbol.

Theverticallinesendinginshorthorizontallinesindicatethe

reliabilityinterval(95%).

TheseresultsshowthatdrivingwithLDWAorFCW/HMW

doesnotresultinahigherorloweraveragespeed.Atthe

sametime,thisvarianceanalysisdoesshowstatisticallysig-

nificanteffects,eventhoseresultingfromsmalldifferences

inaveragespeed(nightversusday:0.3km/h).

Inthesameway,theaveragespeedwasanalysedforthe

othergroupsinSP1andSP3.Theresultsaresummarisedin

Figure33.

Appendix 5: Analysis of measurements taken during field operational test

Figure 32: Average speed as a function of APS, speed limit and half-day (average and 95% reliability interval)

Ave

rage

spe

ed [

km/h

]

limit limitNight Day

Reference

Final report Accident prevention systems for lorries 79

ThepatternarisingfromSP1wasconfirmedinSP3(both

BulkandOEM):effectsofAPSonaveragespeedwerenot

found.

Therewasoneexceptiontothisstatement.Forthe

vehicleswithDCtheaveragespeedwassignificantlylower

[p<0.001]thaninthereferencegroup.Thisconcernsan

effectof1.0km/h.

Data analysis

Foranextensiveanalysis,thereaderisreferredto[16].

ThedivisionintogroupsanalysedandassociatedAPStypes

andvehiclecategoriesisshowninTable20.SP1andSP3

aresimilarintermsofdataregistration,SP2differsfrom

them.Inordertoachievecomparablegroups,theanaly-

sesinthesetwogroupswereperformedseparately.Two

haulierswithdifferentbusinessmodelscooperatedinSP2

(owndriversversusleaseoflorries).Thesearereferredtoas

Haulier1(Tr1)andHaulier2(Tr2).Sincethisfactcouldbe

influential,ithasbeenincludedintheanalysis.

ThenumberoflorriesinChart20islowerthanthenumber

oflorriesinFigure19.Thisisdueinparttotheremoval

fromtheanalysisofanumberoftypesoflorrynecessitated

bytherebeingtoofewofthemtoperformagoodana-

lysis(forexample,some4-axislorries).Inaddition,itwas

foundthatsomeofthelorrieshaddrivenalmostexclusively

outsidetheNetherlands,asaresultofwhichtheyprovided

nodata.

Appendix 5: Analysis of measurements taken during field operational test

Figure 33: Average speed as a function of APS for all subprojects

Chart 20: Classification of APS groups

Ave

rage

spe

ed [

km/h

]

Reference

SP� RetrofitSP3 OEM SP� Drivers

SP3a: Bulk SP3b: OEM Tr� Tr�

APS LDWAFCW/HMWReference

DCLDWA(retro)

Reference

BBFBReference

BBFBLDWA+FCW/

HMWReference

Vehicles ArticulatedlorryMotorisedvehicle

Articulatedcontainerchassis

lorryArticulated

containerlorry

ArticulatedlorryArticulated

containerlorry

Articulatedlorry(4x2en6x2)

Articulatedlorry(4x2)

Number 1.230 143 194 78 487

Data Octo CarrierWeb

Final report Accident prevention systems for lorries80

Analysis of data � (Octo data registration system)

ThesubgroupsSP1andSP3(LDWA,FCW/HMW,DC,

ACC,Octodataregistration)wereanalysedtogether.The

resultsofthiscanbesummarisedasfollowsforeachAPS:

LDWA

• WiththeuseofLDWAtherewerefewerlane

departurewarningsthaninthereferencegroup.

ThisappliedinbothSP1-Retro(11.1versus16.0/h)

andSP3-OEM(5.0versus13.0/h).ForSP3a(bulk)

thefrequencyinthereferencegroupwasalreadylow

andnoimprovementwasachievedwithLDWA(see

Figure34).

• InSP3b-OEMahigherpercentageofheadwaytimes

<1swasfoundforLDWA(18.5%LDWA,12.6%

reference).

FCW/HMW

Nosignificanteffectswerefoundbetweenthepercentage

ofshortheadwaytimes(<1s).Thisalsoappliedtothe

frequencyofFCW/HMWwarnings(p=0.64;averageof

2.93warningsperhourinthereferencegroupand2.89per

hourwithFCW/HMW).

ACC

ForACCvarioussignificanteffectsrelatedtoheadway

behaviourwerefound:

• WithACCtheaverageheadwaytimeislonger

(1.77sACC;1.68sreference).

• WithACCthe%headwaytimes<1sislower

(9.4%ACC;12.6%reference).

• WithACCtherearefewerFCW/HMWwarnings

(0.9/hACC;1.9/hreference)

• WithACCtherearefewerLDWAwarnings

(8.5/hACC;13.0/hreference).

DC

Asalreadyevidentabove,asomewhatloweraveragespeed

occurredwithDC(80.4km/hDC;81.3km/hreference).

Thesamewastrueofthestandarddeviationofthespeed

(3.9km/hDC;4.5km/hreference).

ForLDWA,theAPSDetaildatawasexamined(the10s

fragmentswithdetaileddatastorage)todiscoverthemini-

mumdistancetotheline.ThisisshowninFigure35.

Appendix 5: Analysis of measurements taken during field operational test

Figure 34: Frequency of LDWA warnings as a function of APS for all SPs (average and 95% reliability interval)

LD w

arni

ngs/

h

Reference

Final report Accident prevention systems for lorries 8�

Figure35showsthealertsissuedbytheCliffordElectro-

nics/Mobileye.Thedistancerightisnormallygreaterthan

0;adistancelessthan0meansthatthevehicleleavesthe

laneontherightside.Foraleft-sidelanedeparturethesign

isconverselydefined:thedistanceisnormallynegative;a

distancegreaterthan0meansthatthevehicleleavesthe

laneontheleftside.

Intheanalysistheminimumdistancetothelinewas

determinedforeachavailablefragment.Thesign(both

leftandright)waschosensuchthataminimumdistance

greaterthan0meansthatthevehiclestayswithinthelane.

Aminimumdistancelessthan0indicatesthatthelinewas

crossed.

TheresultsoftheanalysisareshowninFigure36.These

resultsshowthatafterbothagenuineLDwarninganda

silentone,alinecrossingdoesonaverageoccur.Thiscros-

singisintheorderofsizeof20to25cm.

Appendix 5: Analysis of measurements taken during field operational test

Figure 36: Minimum distance to the line after LDWA warning: average and 95% reliability interval (negative means that the line was crossed)

Figure 35: Distance to road lines as a function of time in APS detail fragments, left and right: maintaining a course within the lane (top); maintaining a course with lane crossing (centre); lane change (below)

Reference

min

imum

dis

tanc

e (m

)

dist

ance

(m

)

time (s)

rightleft

dist

ance

(m

)

time (s)

rightleft

dist

ance

(m

)

time (s)

rightleftlane change

Final report Accident prevention systems for lorries8�

LDWAhasaminoreffectonthecrossing:inonlyoneofthe

threesub-groupsdidasignificanteffectoccur(25cmline

crossingwithoutLDWA,23cmlinecrossingwithLDWA).

AsillustratedinFigure37areadingofthedetaileddata

fragmentsalsorevealswhetheralanechangeoccurred.

DetaileddatafragmentswereregisteredonlyifaMobileye

indicatedanevent;lanechangeswherebynoLDWAor

HMWwarningwasgivenarenotpresentinthedata.In

theanalysisitwasdeterminedforeachvehicleinwhat

percentageofthedatafragmentsalanechangeoccurred.

Theaverageofthispercentagewasthenanalysed,broken

downintotypeofAPSsystemandtypeofevent.

Fortheevents‘HMW-red’and‘LDWAleft’alanechange

occurredonaveragein15%to18%ofthecases.This

percentagedidnotdiffersignificantlybetweenlorrieswith

LDWA,FCW/HMWandthoseinthereferencegroup

[F(2,374)=1.1,p<0.33].In‘LDWAright’events,alane

changeoccurredonaverageinjust2%ofthecases.Simi-

larly,inSP3aandSP3bAPShadnoeffectonlanechanges.

Allinall,thedataprovidenoindicationthatAPSinfluences

thepercentageoflanechangesasregisteredinthedata.

Bycontrast,thetypeofeventthatpromptedthestorage

ofthedatafragmentdoesinfluencethepercentageoflane

changes.

Appendix 5: Analysis of measurements taken during field operational test

Figure 37: Percentage van 10s fragments in which lane changes occurred as a function of the type of APS system and of the type of event (SP1)

Chart 21

Reference

Type of APS

% f

ragm

ents

with

lane

cha

nge

‘red’leftright

SP� RetrofitSP3 OEM

SP3a: Bulk SP3b: OEM

APS LDWAFCW/HMWReference

DCLDWA(retro)

Reference

Vehicles ArticulatedlorryMotorisedvehicle

Articulatedcontainerchassislorry

Articulatedcontainerlorry

ArticulatedlorryArticulatedcontainerlorry

Number 1.230 143 194

Data Octo

Final report Accident prevention systems for lorries 83

The10sfragmentswerealsousedtodeterminethe

minimumheadwaytimethatoccurredaftera‘HMW-red’

warning.ForbothFCW/HMWandACC,therewasno

significantdifferencefromthereferencegroup.Theaverage

oftheheadwaytimeminimumswas0.6s.

Tosummarise,theclearesteffectsfortheabove-mentioned

groupsare:

• AnLDWAreducesthenumberofwarningsperhour.

Thus,anLDWAleadstofewerunintentionalline

crossingsorbetteruseoftheindicators.Inonegroupit

wassimultaneouslyobservedthattheshortheadway

timesincrease-anegativeeffect.

• VariouspositiveeffectswerefoundforACC:higher

averageheadwaytimehigher,%headwaytimes<1s

lower,fewerFCW/HMWalertsandfewerLDWA

alerts.

However,whethertheACCwasswitchedonor

offwasnotmeasuredinthetest.Thereforeitcannot

bedemonstratedwhethertheeffectisduetoACCuse

orownership.Thedriversurveysrevealgreatsatisfac

tionwithACC,whichcouldindicateahighlevelof

ACCuse.

Analysis of data � (CarrierWeb data registration system)

ThesecondanalysiswasperformedonthedataforSP2

(BBFB,LDWA+FCW/HMW,CarrierWebdataregistration).

InSP2noACCwasusedbutitwasknownwhetherthe

cruisecontrolwasonoroff.Thisfacthasbeenincludedin

theanalysis.Inaddition,inthisgroupLDWAandFCW/

HMWwereusedonlyincombinationwithoneanother.

Haulier1employsitsowndriversandHaulier2leasesits

lorries.

Tobegin,theeffectsontheaveragespeedarediscussed.

ForHaulier1,thevarianceanalysisshowsthefollowing

effects.

• Thespeedlimithasamarginallystatisticallysignificant

effect[p<0.1].Atahigherspeedlimittheaverage

speedishigher.

• Half-dayhasasignificanteffect[p<0.05].Atnight

theaveragespeedisalittlehigherthanduringthe

daytime,84.9km/hand84.2km/hrespectively.

• Cruisecontrolhasasignificanteffect[p<0.05].

Withcruisecontrolon,theaveragespeedishigher

thanwithcruisecontroloff,85.7km/hand83.5km/h

respectively.

• APShasnoeffect[p=0.3].

Appendix 5: Analysis of measurements taken during field operational test

Figure 38: Effect of the speed limit on the average speed (average and 95% reliability interval)

Ave

rage

spe

ed [

km/h

]

Reference

Limit

Final report Accident prevention systems for lorries84

ForHaulier2,thevarianceanalysisshowsthefollowing

effects.

• Thespeedlimithasastatisticallysignificanteffect

[p<0.001].Atahigherspeedlimittheaveragespeed

ishigher,86.3km/hand85.0km/hrespectively.

• Half-dayhasasignificanteffect[p<0.001].Atnight

theaveragespeedishigherthaninthedaytime,

86.0km/hand85.1km/hrespectively.

• Cruisecontrolhasasignificanteffect[p<0.001].

Withcruisecontrolon,theaveragespeedishigher

thanwithcruisecontroloff,86.8km/hand84.5km/h

respectively.

• APShasaneffect[p<0.05].Forthegroupusing

LDWAandHMW/FCW,theaveragespeedisalittle

lowerthanthatofthereferencegroup,84.4km/hand

85.8km/hrespectively.NoeffectofBBFBonaverage

speedwasfound.

Thus,forbothhaulierstheresultsshownoeffectofBBFB

onaveragespeed.LDWAandHMW/FCWappeartohave

a(small)effectonaveragespeed.Averagespeedwas0.4

km/hlowercomparedtothereferencegroup.

Appendix 5: Analysis of measurements taken during field operational test

Figure 39: Effect of speed limit

Chart 22

Limit

Ave

rage

spe

ed [

km/h

]

Reference

SP� Haulier

Tr� Tr�

APS BBFBReference

BBFBLDWA+FCW/

HMWReference

Vehicles Articulatedlorry(4x2en6x2)

Articulatedlorry(4x2)

Number 78 487

Final report Accident prevention systems for lorries 85

Theresultsaresummarisedasfollowsfortheabove-men-

tionedgroup:

LDWA + FCW/HMW

ThesearetheresultsforHaulier2sinceHaulier1hadno

LDWA+FCW/HMWinitslorries.

• WithLDWA+FCW/HMWtheaveragespeedwas

significantlylower(0.4km/h)thaninthereference

group,85.4km/hasopposedto85.8km/h.

• WithLDWA+FCW/HMWthestandarddeviation

ofthespeedwassignificantlylower(0.1km/h)than

inthereferencegroup,1.68km/hasopposedto

1.78km/h.

BBFB

• Forbothhauliers,theuseofBBFBwasfoundtohave

noeffectonaveragespeed.

• Forbothhauliers,theBBFBhadaneffectonthe

standarddeviationofthespeed.ForHaulier2this

effectwasmarginal(p=0.09).ForHaulier1,theBBFB

wasresponsibleforareducedstandarddeviationofthe

speedcomparedtothereferencegroup(1.38km/has

opposedto1.81km/h).ForHaulier2thestandard

deviationofthespeedwashigherthanfortherefe-

rencegroup,albeitmarginally,1.87km/hasopposed

to1.78km/h.

• TheBBFBwasnotseentohaveanyeffectontheuse

ofcruisecontrol.Ananalysisofthewholedataset,i.e.

bothhaulierstogether,wasperformedforthenumber

oftimesharshaccelerationoccurred(>1.5m/s2)and

thenumberoftimesharshdecelerationoccurred

(<-0.8m/s2).TheBBFBgroupbrakedharshlymargi-

nallylessoften[p<0.1]thanthereferencegroupand

lessoften[p<0.01]thanthegroupwiththeClifford

Electronics/Mobileyesystem(FCW/HMWandLDWA);

[0.011/1000km]asopposedto[0.018/1000km]and

[0.021/1000km]respectively.

Cruise control

• Withthecruisecontrolaneffectontheaveragespeed

wasfoundforbothHaulier1andHaulier2.The

averagespeedwassignificantlyhigher[p<0.001]for

thesituationwithcruisecontrolonasopposedtothe

situationwithcruisecontroloff,85.4km/hasopposed

to83.2km/hand86.7km/hasopposedto

84.0km/h,respectively.

• Aneffectofcruisecontrolwasalsofoundonthe

standarddeviationofthespeedforbothHaulier1and

Haulier2.Thestandarddeviationofthespeedwas

significantly[p<0.001]lowerforthesituationwith

thecruisecontrolonthanwiththecruisecontroloff,

1.0km/hasopposedto2.3km/hand1.0km/has

opposedto2.5km/hrespectively.

Foradetailedanalysis,thereaderisreferredto[19].

Appendix 5: Analysis of measurements taken during field operational test

Figure 40: Number of ‘harsh brakes’ as a function of the system used

SYSTEM

Final report Accident prevention systems for lorries86

TheSWOVhasestimatedforConnekttheeffectsofacci-

dentprotectionsystems(APS)ontrafficsafetyforlorrieson

Dutchmotorwaysastestedinalarge-scaleFieldOperatio-

nalTest(FOT)inthecontextoftheFileProofprogrammeof

theMinistryofTransport.

Thepurposeofthistestwastodeterminethecontribution

thataccidentpreventionsystemsmaketopreventingacci-

dentsor(serious)injuriesandtherebyreducetheincidence

oftrafficjamsandlostvehiclehours.

Thisreportfocusessolelyonthepreventionofaccidents

andrelatestothefollowingsystems:

Headway Monitoring and Warning/Forward Collision

Warning (HMW/FCW)

• wherebyasignalisgivenifaprecedingvehicleistoo

closeorisapproachedtoofast.Thissystemaimsto

preventrear-endcollisions.

Adaptive Cruise Control (ACC)

• wherebyapresetspeedismaintainedandisautomati-

callylowerediftheheadwaytimetothepreceding

vehicledipsbelowthesetvalue.Thissystemaimsto

boostdrivecomfortalthoughitcanalsobeassumedto

helppreventrear-endcollisions.

Lane Departure Warning Assist (LDWA)

• wherebyasignalisgivenifapresetdistancetothe

lanemarkingisbreachedortooquicklyapproa-

ched.Thissystemaimstopreventsingle-vehicle

accidentswherebyavehicledeviatesfromtheroad.

Directional Control (DC)

• asystemthatcontinuouslycomparesthesteeringangle

withwheel(revolution)speedandbrakesperwheelif

thesedeviatefromthenorm.Thissystempreventsa

vehiclefromskiddingorlimitstheconsequencesof

skidding.

Black Box Feed Back (BBFB)

• thedriverisinformedabouthisdrivingbehaviourwith

theaimofimprovingthisbehaviour.Ifsuccessful,this

willhaveaneffectonalltypesofaccident,inprinciple.

ThisSWOVstudyisbasedontheresultsofliterature

research,interviews,questionnairesand(behavioural)

measurementsascollectedbytheprojectorganisation

(Connekt/ITSNetherlands,TNOandBuckConsultants

International),thoughlimitationsdoapplytoafewcases.

TheSWOVundertookanindependentaccidentanalysis

basedonthedataithadavailable.

Bylinkingliteratureknowledge,behaviouralmeasurements

andaccidents,aqualitativeand,wherepossible,quantita-

tiveestimatewasprovidedoftheeffectonvictims.Thefield

operationaltestlimiteditselftoDutchmotorways;reason

fortheSWOVtoalsokeepwithinthislimit.

ForDirectionalControlitisestimatedthatthissystemon

Dutchmotorwayscanprevent1deathand5-8hospitalisa-

tionseachyearifpresentinalllorries.

ForAdaptiveCruiseControl,thiscanbeassumedtohavea

positiveeffectonsafety,thoughthiscannotbequantified

onthebasisoftheinformationcurrentlyavailable.

Appendix 6: Summary of SWOV report

Final report Accident prevention systems for lorries 87

Literaturesuggeststhatapositivebehaviouraleffectcould

beexpectedfortheothersystems(HMW/FCW,LDWAand

BBFB)butthiswasnotconfirmedbythemeasurements.

Themeasurements,literatureanddiscussionsprompted

hypothesesthatcouldbeverifiedinafollow-upstudyand

thismaywellleadtomodificationsoftheaccident

protectionsystemswherea(measurable)safetyeffectcan

beachieved.

Tobeabletoascertainwhethertherecommendationshould

promoteorcompeltheuseofaccidentpreventionsystems

inlorriesfromatrafficsafetyperspective,furtherresearch

isdesirable.Thismayinthefirstinstancetargetamore

penetrativeanalysisofthedatacurrentlyavailable.Itisalso

necessarytoincludeothertypesofroadthanmotorways

inthisstudysincesafetycouldalsobeenhancedonsuch

roads.

Appendix 6: Summary of SWOV report

Final report Accident prevention systems for lorries88

PublicationConnekt/ITSNetherlands

Kluyverweg6,2629HTDelft

P.O.Box48,2600AADelft

TheNetherlands

Tel.+31152516565

Fax.+31152516599

info@connekt.nl

www.connekt.nl

Design and productionH.U.MCommunication&GraphicDesign,Rotterdam

DisclaimerCopyrightholderofthisreportisConnekt/ITSNetherlands.

Nothingfromthispublicationmaybeduplicatedor

publishedwithoutwrittenpermissionfromConnekt/ITS

Netherlands.Thestatementsinthispublicationarenot

binding.ThecollecteddataintheFieldOperationalTest

isownedbytheMinistryofTransport.

ThispublicationhasbeenmadepossiblebyTNOandBuck

ConsultantsInternational.

September2009

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