Driver Behavior at the Onset of Yellow Indication for Rainy/Wet Roadway Surface Conditions

The paper characterizes the impact of wet pavement surface and rainy weather conditions on driver behavior at the onset of a yellow indication on high-speed signalized intersection approaches in a controlled field environment using an in-vehicle differential Global Positioning System (GPS). Twenty-six drivers were recruited in three age groups (under 40-years-old, 40 to 59-years-old, and 60 years of age or older) with an equal number of male and female participants. The driver stopping/running decisions are analyzed for six trigger distances, measured from the vehicle position to the stop bar when the 4-second yellow indication starts, as drivers approach the intersection at a speed of 72 km/h (45 mi/h). The study characterized the impact of roadway grade, driver gender, driver age, and time-to-intersection on the driver stopping/running decisions. The 0.9/0.1 probability of stopping/running was 3.9 s from the stop line at the onset of yellow, while the 50 percent stopping/running decision point occurred when the yellow indication was triggered while the vehicle was 3.0 s from the stop line. Dilemma zone boundaries obtained were statistically significant, started 0.1 second farther from the stop bar, compared to clear weather condition. Male drivers show slight differences in stopping/running behavior when compared to female drivers but with no significant differences between male and female drivers. The study demonstrates that drivers 60 years of age and older are significantly less likely to run, at the onset of the yellow indication, at short yellow-indication trigger times when compared to other age groups. Furthermore, the study demonstrates a decrease in the probability of stopping on wet pavement surface and rainy weather conditions when compared to clear weather condition.