Measuring the Impacts of Speed Reduction Technologies:

A Dynamic Advanced CurveWarning System Evaluation

Casey N. Nolan Casey N. Nolan Masters of Urban and Regional Planning, CandidateMasters of Urban and Regional Planning, Candidate

January 10January 10thth, 2005, 2005Transportation Research Board Transportation Research Board

8484thth Annual Meeting Annual Meeting

Co Authors: Co Authors: Robert L. Bertini, Chris Monsere, Robert L. Bertini, Chris Monsere,

Tarek Abou El-Seoud, Tarek Abou El-Seoud, Edward AndersonEdward Anderson

BackgroundBackground

Identified as a problem areaIdentified as a problem area Sharp curve & excessive speedSharp curve & excessive speed High crash frequency rateHigh crash frequency rate

ODOT installed Changeable Message SignsODOT installed Changeable Message Signs April 2004April 2004 Uses radar to display speedsUses radar to display speeds

Portland State UniversityPortland State University Classic before/after studyClassic before/after study

Crash History (1998-2002)Crash History (1998-2002)

Crash rate above averageCrash rate above average 1.18 per MVMT vs. 0.22 per MVMT1.18 per MVMT vs. 0.22 per MVMT

33 reported crashes 33 reported crashes 13 crashes southbound13 crashes southbound 20 crashes northbound20 crashes northbound

12 injuries (3 severe)12 injuries (3 severe)

70% of crashes involved one vehicle70% of crashes involved one vehicle

More truck crashes southboundMore truck crashes southbound 11 overturning incidents11 overturning incidents

Other Similar ApplicationsOther Similar Applications

Truck RolloverTruck Rollover California (I-5 Sacramento River Canyon)California (I-5 Sacramento River Canyon) Texas (freeway off-ramp loops)Texas (freeway off-ramp loops) Maryland and Virginia (freeway off-ramp loops – Maryland and Virginia (freeway off-ramp loops –

with WIM, speed, height detection)with WIM, speed, height detection)

Truck Downgrade WarningsTruck Downgrade Warnings Colorado (I-70, Eisenhower Tunnel)Colorado (I-70, Eisenhower Tunnel) Oregon (I-84, Emigrant Hill)Oregon (I-84, Emigrant Hill)

LocationLocation

Near MP 108 Near MP 108 on I-5 in on I-5 in southwest southwest OregonOregon

Geographic Geographic constraints constraints necessitate necessitate undesirable undesirable highway highway geometry geometry

Myrtle Creek CurvesMyrtle Creek Curves

Northbound Sign

Southbound Sign

N

InstallationInstallation

Changeable Message Signs (CMS)Changeable Message Signs (CMS) Used existing sign bridges in both directionsUsed existing sign bridges in both directions

Radar UnitRadar Unit Pole-mounted, 20ft highPole-mounted, 20ft high Doppler technologyDoppler technology

Vehicle speedsVehicle speeds

Travel directionTravel direction Detects “fastest signal”Detects “fastest signal”

$140,000 total system cost $140,000 total system cost

CMS MessagesCMS Messages

PanelPanel Default MessageDefault Message

Speeds less Speeds less than 50 mphthan 50 mph

WarningWarningMessageMessage

Speeds 50 Speeds 50 to 70 mphto 70 mph

Excessive Speed Excessive Speed MessageMessage

Speeds over Speeds over 70 mph70 mph

11 CAUTIONCAUTION SLOWSLOWDOWNDOWN

SLOWSLOWDOWNDOWN

22 SHARPSHARPCURVESCURVESAHEADAHEAD

YOURYOURSPEED ISSPEED ISXX MPHXX MPH

YOURYOURSPEED ISSPEED IS

OVER 70 MPHOVER 70 MPH

Northbound PicturesNorthbound PicturesBefore

After

Southbound PicturesSouthbound Pictures

Before

After

Objectives of the Objectives of the Myrtle Creek StudyMyrtle Creek Study

Before and after analysis Before and after analysis Crash frequencyCrash frequency Speed data Speed data

Post-installation driver awarenessPost-installation driver awareness Motorist surveyMotorist survey

Measures of EffectivenessMeasures of Effectiveness

Change in mean speed Change in mean speed Passenger cars Passenger cars Commercial vehiclesCommercial vehicles

Change in speed distribution Change in speed distribution Passenger cars Passenger cars Commercial vehiclesCommercial vehicles

Public response to the signPublic response to the sign

Speed Data CollectionSpeed Data Collection

SamplingSampling 4 before days 4 before days 3 after days3 after days

TechniqueTechnique UltraLyte laser speed detector & computerUltraLyte laser speed detector & computer Passenger vs. commercial vehiclesPassenger vs. commercial vehicles

Data Collection LocationData Collection Location

Southbound – Southbound – Data collected from Data collected from

vehicle in ramp gorevehicle in ramp gore

Northbound – Northbound – Data collected from Data collected from

behind concrete barrier behind concrete barrier downstream from the downstream from the sign bridgesign bridge

Data AnalysisData Analysis

Cosine correctionCosine correction No road geometry adjustmentNo road geometry adjustment

Commercial vs. Passenger vehiclesCommercial vs. Passenger vehiclesData analyzed in 200 foot binsData analyzed in 200 foot bins Distance from sign bridgeDistance from sign bridge

Statistics used for comparisonStatistics used for comparison MeanMean Standard deviationStandard deviation 9595th th percent confidence intervalpercent confidence interval

Comparison of Mean Zones - Southbound, Passenger Vehicles

50

52

54

56

58

60

62

-1300 -1100 -900 -700 -500 -300 -100 100 300 500 700 900

Zone Location (feet from s ign)

MP

H

Before Mean

After Mean

Sign Start of CurveSign Vis ible

Travel

ResultsResults

Comparison of Mean Zones - Southbound, Commercial Vehicles

45

46

47

48

49

50

51

52

53

54

55

-1300 -1100 -900 -700 -500 -300 -100 100 300 500 700 900

Zone Location (feet from s ign)

MP

H

Before Mean

After Mean

Sign Start of CurveSign Vis ible

Travel Direction

ResultsResults

Comparison of Mean Zones - Northbound, Passenger Vehicles

46

48

50

52

54

56

58

60

62

64

-900 -700 -500 -300 -100 100 300 500 700 900 1100 1300

Zone Location (feet from sign)

MP

H

Before Mean

After Mean

Sign Start of CurveSign Vis ible

Travel Direction

ResultsResults

Comparison of Mean Zones - Northbound, Commercial Vehicles

44

46

48

50

52

54

56

58

-900 -700 -500 -300 -100 100 300 500 700 900 1100 1300

Zone Location (feet from sign)

MP

H

Before Mean

After Mean

Sign Start of CurveSign Vis ible

Travel

ResultsResults

Speed DistributionsSpeed Distributions

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

35-<40 40-<45 45-<50 50-<55 55-<60 60-<65 65-<70 >70

Speed Category

Before

After

At nearest rest areaAt nearest rest area NB – 35 miles northNB – 35 miles north SB – 26 miles southSB – 26 miles south

Northbound & Southbound Combined, n = 87Northbound & Southbound Combined, n = 87 85% passenger vehicles85% passenger vehicles 90% noticed sign90% noticed sign 74% saw speed displayed74% saw speed displayed 81% useful information81% useful information 77% adequate location77% adequate location 89% visibility adequate89% visibility adequate

Survey ResultsSurvey Results

ConclusionsConclusions

Reduction of speeds for majority of Reduction of speeds for majority of vehiclesvehicles 3 mph SB3 mph SB 2 mph NB2 mph NB

Public response to the device was positivePublic response to the device was positive

Need to monitor crashes for some timeNeed to monitor crashes for some time

Thank You!Thank You!

Casey Nolan

Masters of Urban and Regional Planning Program

Portland State University

cnn@pdx.edu

Acknowledgements

Dr. Robert L. Bertini & Dr. Christopher Monsere, of Portland State University

Edward Anderson & Rob Edgar, of Oregon Department of Transportation

Dr. Thomas Kimple, Steve Hansen & Matt Lasky, of Portland State University