Evaluation of an alternative traffic light change anticipation system

A driving simulator was used to study the efficacy of an alternative signal phasing program. The new Traffic Light Change Anticipation System (TLCAS) utilizes a flashing amber in conjunction with a solid green indication to warn drivers of the impending onset of the solid amber indication. This new program was expected to provide drivers with additional information with which to make safe stopping or crossing decisions, and reduce behavior associated with increased accident rates at signalized intersections. Additionally, a new measure of first response variability was introduced to evaluate the effect of the new program on driver behavior. The results indicated that the new system has the ability to reduce the number of red light violations. Of the 1148 target intersections, 43 violations were recorded for the regular program compared to 9 for the TLCAS program. The severity of decelerations was also impacted. The regular program displayed average maximum decelerations of 3.1 m/sec² compared to 2.5 m/sec² for the TLCAS program. However, the TLCAS program showed an increased variability in first response five times larger than the regular program. This finding, in conjunction with traditional measures, indicates that the new system performs comparably to an increased amber duration by increasing the potential for conflicting decisions between successive drivers approaching an intersection. Altogether, the results suggest that this alternative signal phasing program would not improve intersection safety. The findings also suggest that further study of the longitudinal behavior after the introduction of a TLCAS program may be warranted. Specifically, future studies should examine whether subjects engage in appropriate adaptive changes when confronted with a solid amber period warning after becoming familliar with the TLCAS.