Preliminary Impact Analysis of Countdown Signal Timer Installations at two Intersections in Greece

The objective of the paper is to identify the change of the compliant (or non-compliant) behavior of car drivers due to the existence of a countdown signal timer, installed at urban intersections. For that reason, on field observations were taken place at two intersections located in a mid-sized city of northern Greece. A countdown signal timer was installed at the first intersection whereas no such installation existed for the second one. The two intersections are located close to each other and therefore comparative assessment on the safety improvement due to the presence of the installation was deemed possible. In total, 5098 observations were recorder in 10 days within 60 hours, for three different periods of the day (morning, afternoon and evening). The observations were mainly focused on compliance behavior of each driver in the sample, for two specific events: a) prior to the onset of the green phase (early vehicle move) and b) green phase termination (driver speeds up to cross intersection). Among other important outcomes, the analysis revealed that CST devices tend to make drivers more aggressive as they are waiting for the onset of the green phase. The percentage of the violations of the early start for the signal with the CST device was observed to 24% whereas the respective percentage for the signal without the CST installation was less than 1%. On the other hand, the analysis indicated that CST devices make drivers to be more compliant with the signal indications when the green phase is going to be terminated; it was found that CST devices can reduce drivers’ decision to cross the interchange by a percentage of 15%.