Do professional drivers suffer from dilemma zone problem while facing amber light?

Abstract

Signal controlled junction, which is a good measure to cater for conflicting traffic in heavily trafficked intersections, has been widely adopted in urban road networks. Traffic flow distributions, delay on road users, and more importantly road safety are the major considerations when designing junctions. Numerous studies have been conducted attempting to strike a balance between these three aspects by extending the green or yellow time in case of vehicles fall within dilemma zone (DZ) to avoid conflicts. In this study, a new proposed parameter termed "perception" was adopted to quantify the favorability of recorded vehicles in making STOP/GO decisions and to assess drivers' performance in making stop/go decisions while facing amber light. Paired t-test was used to check the proposition that (1) whether the situations of approaching vehicles at the amber onset at the studied signalized junction is generally favorable to GO; (2) whether professional drivers including Public Bus, Public Light Bus, Taxi and Goods Vehicle drivers suffer from DZ problem in making STOP/GO decision while facing amber; and (3) attempt to figure out the worst decision making performance area of observed drivers at the junction considered in this study. The results of this study indicate that the situations of drivers that were observed in the studied junction were generally favorable to GO and virtually all the observed drivers aware of their favorable choices while facing amber light. In other words, drivers that were observed in this study do not suffer from DZ problem. The results also indicate that Taxi drivers are comparatively worse in making STOP decision while facing amber light compared to Public Bus, Public Light Bus, Goods Vehicle and Private Car drivers, but this is subject to speeding problem that should be prohibited. In addition, the worst decision making performance area was found at approximately 44 to 48m from stop line (i.e. 3.2 to 3.5 seconds travel time from stop bar) that is slightly larger than travel distance covered by 3 seconds amber time. Further comprehensive analyses on whether or not drivers suffer from DZ problem at signalized junctions with difference geometry layouts and traffic conditions in Hong Kong are required to evaluate if there is a need to provide DZ avoidance measures and thus to improve junction design in safety respect.