Effects of countdown timers on traffic safety at signalized intersections

Improving safety is one of the most important tasks of traffic engineering. In the road network, intersections are the places where conflicts most often occur. Therefore, these objects are of particular interest to engineers, designers and researchers. The possibilities of using modern technologies give a chance not only to achieve greater traffic efficiency, but also to ensure safe passing for all road users. One of such solutions are countdown timers, i.e. support devices for traffic lights which show the time (in seconds) remaining before the currently displayed signal on traffic light change. In some Polish cities those devices are installed on a growing number of intersections. However, the introduction of such new solutions without prior examination of their impact on safety is not recommended. The use of countdown timers at signalized intersections changes the way traffic control signals are perceived by drivers. To compare the impact of the device on the behavior of drivers, three different intersections have been selected depending on the function of the intersection in the transportation network. The measurements were made in two periods of research: for a week with enabled and disabled countdown timer devices. This article is a continuation of the previous research work carried out by the authors on determining the impact of the countdown timers on traffic conditions. The aim of this article is to show results of the analysis of the time distribution of vehicles entering the crossroads during the red signal for different type of the intersections. The results of the case study show that the countdown timer devices improve safety. Depending on types of intersections during the research with the enabled countdown timers from 22,65% to 32,03% less of the vehicles drove into the crossroads in a prohibited period.