EVALUATION OF DRIVER BEHAVIOR AT SIGNALIZED INTERSECTIONS (DISCUSSION)

Time-lapse photography was used to study driver behavior associated with the traffic signal change interval at a total of six intersections in the Phoenix and Tucson metropolitan areas. In addition, nighttime studies were conducted at two of these intersections. An evaluation of the time-lapse film permitted the determination of the approach speeds of the vehicles, the average deceleration rates of the stopping vehicles, the perception-reaction times of the drivers of the stopping vehicles, and the distance that the vehicle was from the intersection at the onset of the yellow interval. The distance from the intersection was measured for both the stopping vehicles as well as those that proceeded through the intersection. The results of the study indicated that the mean deceleration rates at the six sites ranged from 7.0 to 13.9 ft/s/s, and the mean value for all observations was 11.6 ft/s/s. The observed mean perception-reaction time was approximately 1.3 s while the 85th percentile times ranged from 1.5 to 2.1 s. Comparisons of intersections with yellow only versus yellow plus all-red intervals produced mixed results in terms of differences in observed behavior. Even for intersections with the same change interval design, there were cases where the observed deceleration rates were significantly different.