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
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