The effect of countdowntimers on traffic flow and safety

Abstract

This thesis describes a driving simulator study that was performed to assess the effects of numerical countdown timers at traffic lights on Belgian driving behavior. The purpose of such devices is to warn drivers that the oncoming phase change is about to happen and should help drivers to start earlier at the onset of the green phase and offer aid in their stopping decision at the onset of the amber phase. Three configurations were tested: no timer, a final-stage countdown timer or an entire-phase countdown timer. Six unique conditions were developed, in which each configuration was encountered during a dilemma zone and a situation in which the traffic light turn to red during the approach. The results indicated that the countdown timers increased the amount of stopped vehicles for the dilemma zone scenarios. Furthermore, maximum applied deceleration forces were twice and three times as low for the final-stage and entire phase countdown timers, compared to the reference condition. With regard to the onset of the green phase, a reduction of around 1,1 second for the reaction time and start-up lost time was found. This study concluded that countdown timers for the green phase decreased the traffic flow efficiency, but improved traffic safety levels. With regard to countdown timers for the red phase, it was concluded that traffic flow efficiency could be improved, without compromising on traffic safety aspects. No statistically significant differences between the two forms of countdown timers were found.