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Driver and Surrounding Traffic Impact on Vehicle Deceleration Behavior at the Onset of a Yellow Indication Ihab El-Shawarby, Hesham Rakha, Ahmed Amer & Catherine McGhee 1. Paper Objectives 3. Experimental Design To characterizes driver deceleration levels in a controlled The field experiment was conducted at the VDOT’s Smart Road facility located at the Virginia Tech Transportation Institute. field environment at the onset of a yellow indication on The horizontal layout of the test section is fairly straight and the vertical layout has a substantial grade of 3%. high-speed signalized intersection approaches using an Half the trials run by each participant were on a 3% upgrade and the other half were on a 3% downgrade. in-vehicle differential Global Positioning System (GPS). The test participants drove the entire 2.6 km test course 48 times (24 uphill and 24 downhill). To characterize the impact of driver gender, driver age, 4 yellow interval repetitions at 6 trigger distances and additional 24 green trials. roadway grade, mean approach speed, platooning 24 participants, equal number of male & female drivers, ages range from 21 to 80. scenarios (leading, following, or alone), and time-to- intersection (TTI) on the driver deceleration levels. This 2 instructed speeds of 72.4 km/h (45 mi/h) and 88.5 km/h (55 mi/h). characterization is critical for the efficient and safe design 3 platoon conditions (leading, following, or no other vehicle) with a 2nd confederate vehicle crossing intersection from the side street. of traffic signal clearance timings within the IntelliDrive 4. Deceleration Level Measurements and Analysis initiative. 2. Introduction platoon, trial number, and condition were reported in the data file. The data that were gathered included but were not limited to: current state and duration of thet number, age, and gender),jecVideo and vehicle performance data were assembled digitally from the test vehicle DAS. Video frame, driver’s information (sub Driver deceleration levels are critical in the design of traffic signal, heading of the vehicle clockwise from north (deg), vehicle speed (mi/h), acceleration (g), distance to intersection stop bar (ft), TTI computed as yellow-interval timings. In addition, driver deceleration distance/speed (s), time-to-yellow (s), percentage of throttle application (percent), brake application (on/off), and distance between confederate and subject levels play a critical role in most traffic simulation software vehicle (ft). 180 88 Km/h Instructed Speed 7 7 (a) 72 Km/h Instructed Speed 7 (a) 72 Km/h Instructed Speed72 Km/h Instructed Speed200 and vehicle fuel consumption and emission models. 160 6 ) 6 ) 6 of deceleration lane lengths. Number of Observations 100 2 3 Deceleration Rate (m/s 2 Older 2 2 NoOther543Deceleration Rate (m/s543254)Deceleration Rate (m/s80140120designtheincriticalarelevelsdeceleration Furthermore, The state of practice is to assume a constant deceleration 40 2 0 Younger 0 FollowingLeading1Middle160 level of 3 m/s2 or 10 ft/s2. 20 1 72 Km/h Instructed Speed 2 2.5 3 TTI (s) 4 4.5 5 2 2.5 3 TTI (s) 4 4.5 53.53.5 0 88 Km/h Instructed Speed 65 70 75 80 85 90 95 Previous studies have either been conducted in a driving 140 (a) 72 Km/h Instructed Speed Profile of the two approach speeds 02 2.5 3 TTI (s) 4 4.5 5 7 (b) 88 Km/h Instructed Speed 7 (b) 88 Km/h Instructed Speed3.5Approach Speed (Km/h)160 recording driver behavior, or in a controlled field Number of Observations 100 Grade Downhill 440 Min Max Mean 15% 50% 85% Std. Div. 7 (a) 72 Km/h Instructed Speed 7 (a) 72 Km/h Instructed Speed 2 4 2 45)Deceleration Rate (m/s5)Deceleration Rate (m/s0.710.714.374.483.543.583.003.123.653.757.317.252.312.31N532UphillVariable80120randomly66sdeceleration levelonvehicle speedEffect ofPlatoonfor Grade, Age, Gender and)2(m/sevelLecelerationDDescriptive Statistical Results ofbyfieldthefromgatheredor simulator, vehicles. This study is unique because it combines 20 Age Middle 345 2.31 7.31 3.69 2.98 3.50 4.46 0.83 Deceleration Rate (m/s 3 Deceleration Rate (m/s 3 0 Younger 0 FollowingNoOtherLeading21OlderMiddle215425420.790.684.454.513.563.613.063.153.743.777.316.312.312.51509317MaleOlder876543210040))Genderother33660.614.343.553.053.655.522.42462Female60withinteractiontheconsideringwithout environment several aspects: Deceleration Rate (m/s2) Following 309 2.42 7.31 3.74 3.11 3.60 4.46 0.70 2 2 2 2.5 3 TTI (s) 4 4.5 5 2 2.5 3 TTI (s) 4 4.5 53.53.50.584.243.563.043.635.402.42309Younger (a) Detailed driver information was available and the 140 Single 338 2.42 7.20 3.65 2.98 3.50 4.40 0.72 02 2.5 3 3.5 4 4.5 5 02 2.5 3 3.5 4 4.5 Male 51Uphill10.71FemaleDownhill Effect of age on deceleration levels Effect of surrounding traffic on deceleration levels0.714.384.393.553.553.103.053.713.707.257.312.312.31325971LeadingPlatoonOverall(b) 88 Km/h Instructed Speed160 breakdown. Number of Observations 100 Variable 544 (a) 72 km/h instructed speeds 50% 85% Std. Div. 7 (b) 88 Km/h Instructed Speed 7 (b) 88 Km/h Instructed Speed Differences of Least Squares Means Using Linear Mixed Model ApproachPr >|t|825.t ValueDownhillVariableUphillEffectGrade0.724.553.823.1915%3.87Mean7.28MaxMin2.43NUphill80120driverTTI (s)TTI (s)desiredtheachievetoconstructedwaspool driver which allowed for the gathering of deci-second vehicle Histogram of the deceleration levels Age Younger 319 2.51 5.81 3.75 3.15 3.70 4.39 0.61 2 2 Platoon Single Leading -0.44 0.65840.000264.4-OlderMiddle330.854.593.763.073.887.282.43366Middle8Deceleration Rate (m/s1770.90.000380.14.3-MiddleOlderYoungerYoungerAge50.0809841.-aleMFemaleGender4)254)2Deceleration Rate (m/s0.690.780.694.584.644.863.753.883.983.153.203.333.843.964.086.477.285.892.302.432.30489556360FemaleMaleOlderGender76)5243Deceleration Rate (m/s21004020with0.7630.57-km/h88km/h72Speed664.733.803.173.947.282.30501DownhillGrade60(DAS),equippedSystemwereAcquisitionvehiclesDataaandconfederateGPSandtestThedifferential(b) a and brake pedal information. Platoon Leading 351 2.52 7.28 3.89 3.16 3.80 4.59 0.75 02 2.5 3 3.5 4 4.5 5 02 2.5 3 3.5 4 4.5 Male 5 Leading Following -2.65 0.01101Uphill1Female0.00323.11-FollowingSingleDownhill0.720.754.784.573.883.783.193.183.963.877.287.182.512.30336358FollowingSingle (c) The communication between the test vehicle and Conclusions Overall 1045 (b) 88 km/h instructed speeds 3.82 4.61 0.74 Effect of roadway grade on deceleration levels Effect of gender on deceleration levelsTTI (s)TTI (s)3.173.917.282.30 traffic signal ensured that the yellow time was started 2 deceleration level used in the state-of-the-practice traffic signal designm/s3The results indicate that driver deceleration levels are significantly higher than the when the vehicle was at pre-selected distances from the guidelines, the mean deceleration level is more in the range of 3.6 to 4.1 m/s2. intersection and thus direct comparisons could be made and statistical tests could be conducted. Deceleration levels are higher at shorter TTIs at the onset of yellow, drivers are willing to exert deceleration levels of 7 m/s2 at short TTI (2.5 s). (d) This study was conducted in a controlled field with Younger (less than 40 years of age) and older (greater than 60 years of age) drivers employ greater deceleration levels compared to middle-aged drivers . surrounding confederate vehicles to simulate real-world A driver following another vehicle that proceeds through the intersection exerts higher deceleration levels compared to drivers driving alone or leading another conditions and thus driver behavior could be recorded vehicle considering the interaction with surrounding traffic. Drivers leading a platoon of vehicles are not affected by the vehicles behind them with regards to their deceleration behavior. Acknowledgments The authors acknowledge the support of the Center for Technology Development and the researchers in the Center for Sustainable Mobility at VTTI for assisting running the tests. This work was supported in part by grants from the Virginia Transportation Research Council, SAFETEA-LU funding, and the Mid-Atlantic Universities Transportation Center.
