STOP AHEAD AND STOP SIGNS AND THEIR EFFECT ON DRIVER EYE SCANNING AND DRIVING PERFORMANCE

The objective of this study was to determine the effectiveness of the STOP AHEAD sign in warning drivers of an upcoming, unexpected, partially concealed STOP sign and intersection during daytime and nighttime driving conditions. The driving performance and eye-scanning behavior of 39 subjects was studied as they approached an intersection (from the north and southbound directions) of two two-lane rural roads where they were required to stop. Each test driver was subjected to only one condition, which was the same for both intersection approaches (day or night, with or without the STOP AHEAD sign) and belonged to a group of three to six experienced or inexperienced drivers. The results show few statistically significant differences in driver eye-scanning and control behavior (velocity, longitudinal deceleration, gas pedal deflection, lateral lane position, and brake activation) between Run 1 and Run 2 and between inexperienced and experienced drivers. However, the test drivers approached the STOP sign with lower average velocities and lower average longitudinal decelerations near the STOP sign at night when the STOP AHEAD sign was present than when it was not present. Despite this fact, 10 of the test drivers were unable to come to a complete stop at the intersection (eight of the improper stops occurred when the STOP AHEAD sign was present). Although the STOP AHEAD sign seemingly influenced the test drivers' behavior at night, it is concluded that STOP AHEAD signs with STOP AHEAD written on their face do not give drivers adequate visual stimulus to prepare them to stop when approaching an unexpected, partially concealed intersection.