Abstract
Intersections, for vehicles coming from different directions, are conflict points in road networks. When a driver approaching a signalised intersection encounters the yellow light, he/she is in a dilemma either to safely stop or to pass through the intersection during clearance time. The decision to stop or to pass may change depending on some factors such as duration of yellow light, deceleration and acceleration rate, width of intersection, speed and length of vehicle, etc. This study aims to put forth the effects of some related factors affecting the length of the Type I dilemma zone. To perform this study, five factors including vehicle speed, maximum deceleration rate, perception-reaction time, clearance time, the total intersection width-vehicle length were considered and a total of 648 different traffic cases were investigated. The study results showed that the Type I dilemma zone length increased with the increase of speed, total intersection width-vehicle length and perception-reaction time, but decreased with the increase of clearance time and deceleration rate.
Highlights
Intersections are potential accident areas in road networks because two or more traffic streams cross or merge on the approach
Traffic signalisation mostly prevents traffic accidents at intersections, collisions occur for various reasons such as driver behaviours, speed, the duration of perception-reaction time and yellow time
It is noted that the Type I dilemma zone length enlarges with the increase of speed yet decreases with the increase of deceleration rate, as shown in Figure 4, Tables 4 and 5
Summary
Intersections are potential accident areas in road networks because two or more traffic streams cross or merge on the approach. Gazis et al first introduced this safety problem at signalised intersections to traffic engineering literature as a dilemma zone problem They defined the dilemma zone (DZ) as a zone that vehicles at the onset of the yellow indication neither stop safely nor pass clearly through the intersection before the stop line [9]. It has been recognised that longer yellow or clearance intervals could eliminate the Type I dilemma zone; it would lead to longer option zones where drivers are indecisive to stop or cross at the onset of yellow light. Zegeer and Deen suggested an approach to defining the boundaries of the Type II dilemma zone depending on the driver’s decisionmaking They expressed the dilemma zone as a zone where more than 10% and less than 90% of drivers would choose to stop at the start of the yellow signal [32]. The analysis of the factors that could affect the dilemma zone has been one important issue of traffic engineering
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