This study analyzes field data gathered from 60 test subjects to characterize driver deceleration rates at the onset of a yellow-phase transition on high-speed signalized intersection approaches using an in-vehicle Global Positioning System. The driver rate of deceleration is analyzed for five yellow-phase trigger times to stop line (1.6, 2.7, 3.3, 4.4, and 5.6 s) as drivers approach the intersection at a speed of 72 km/h (45 mph). Results of the study, based on a sample of 821 deceleration events, indicate that driver deceleration rates range between 1.51 and 7.47 m/s2 (5–24.5 ft/s2) with a mean value of 3.27 m/s2 (10.7 ft/s2). Mean deceleration rates varying from 2.2 m/s2 (7.2 ft/s2) for the longest time to stop line (5.6 s) to 5.9 m/s2 (19.4 ft/s2) for the shortest time to stop line (1.6 s) demonstrate that drivers use more time to decelerate if they are sufficiently away from the intersection. Statistical analyses were used to investigate the effects of the time to stop line, gender, age group, and grade on the average deceleration rates. Results demonstrate that male drivers appear to show slightly higher rates of deceleration when compared with female drivers. This difference increases as the trigger time to stop line decreases. Younger drivers (younger than 40 years old) and older drivers (60 years of age or older) exhibit greater deceleration rates when compared with drivers in the 40- to 59-year age group.
The potential effectiveness of warnings to drivers in imminent danger of collision with a red light violator was evaluated in an experiment that used a driving simulator. Three warnings were tested: (a) an infrastructure-based warning that immediately turned the traffic signal red and activated red wig-wag lights; (b) an in-vehicle warning that consisted of a brake pulse, voice annunciation, and activation of a red dashboard light; and (c) simultaneous activation of both warnings. Three warnings were tested with different groups of drivers. Drivers in each group were also exposed to one of three traffic conditions: (a) no other vehicles ahead or behind, (b) following closely behind another vehicle, and (c) being closely followed by another vehicle. Individual drivers received only one warning on only one trial. The warnings were given on approach to the intersection at a point where the probability that the driver would stop for a yellow change interval was less than 10%. All three warnings proved effective in delaying drivers' arrival at the intersection by at least 1 s. The simultaneous in-vehicle and infrastructure warning was significantly more effective than the other warnings and delayed 95% of drivers. The infrastructure-only and in-vehicle-only warnings delayed 67% and 80%, respectively. The presence of leading or following vehicles had no detectable effect on the probability response to the warning.
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