Evaluating Impacts of Flashing Green before Amber on Drivers' Stop/Cross Decisions at Signalized Intersections in China: an empirical approach and comparative study

摘要

To better understand the safety effects of flashing green before amber on signalized intersections inChina, this study compares drivers' stop/cross decisions at the onset of the amber phase at signalizedintersections with and without flashing green, based on data collected from six approaches withsixteen exclusive through-lanes at five signalized intersections during on-peak and off-peak hours. Itis found that flashing green installation serves only to encourage stopping but does not curb red lightviolations. In effect, flashing green adversely increases red light violations during off-peak hours dueto a lengthier option zone. Meanwhile, flashing green induces aggressive drivers to pass the stop-lineduring amber with significantly higher speeds during off-peak hours. This effect is due to the realityof unreasonable legal regulations and acquiescence with respect to crossings by acceleration duringamber in China. More specifically, the introduction of flashing green further expands the differencebetween drivers' acceleration/deceleration decisions, which is clearly expressed in the higher standarddeviations of vehicular speeds while passing the stop-line at sites with flashing green. Moreover,flashing green alleviates drivers' underestimation of the time to the end of the amber phase, whichmay reduce early stops but does not sacrifice safety overall. However, flashing green apparently failsto work normally during on-peak hours. It has limited impacts on vehicular speeds, the proportions ofamber-light running and red light violations, evidently due to car-following characteristics atintersections during on-peak hours.