An Analysis of the Dilemma Zone Problem at High-Speed Signalized Intersections with the SA Control Strategy

Drivers approaching an intersection when the traffic lights change to amber have to decide whether to stop or to continue through the intersection. A dilemma zone is a stretch of the approach to an intersection within which the decision as to whether to go or to stop is clear cut. At higher speeds some drivers may be caught in a position where the must choose to either brake sharply to stop or continue and risk entering the intersection during the red. This can have safety implications as there is the potential for conflicts with other road users. This paper suggests a probabilistic model for the analysis of the dilemma-zone problem at high-speed signalized intersections with the speed assessment (SA) control strategy. Methods for the calculation of the probability of the maximum change and that of a driver being caught in a dilemma zone will be presented and documented using numerical calculations based on different definitions of dilemma zones found in the literature. The effects of traffic demand and traffic control parameters such as maximum green will be discussed.