American Society of Civil Engineers

Stochastic Dilemma Hazard Model at High-Speed Signalized Intersections

by Pengfei Li, Ph.D., (Ph.D. Candidate and Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ. (Virginia Tech), Blacksburg, VA 24061. E-mail: and Montasir Abbas, Ph.D., P.E., (corresponding author), (Assistant Professor, Dept. of Civil and Environmental Engineering, Virginia Polytechnic Institute and State Univ., Blacksburg, VA 24061 E-mail:

Journal of Transportation Engineering, Vol. 136, No. 5, May 2010, pp. 448-456, (doi:

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Document type: Journal Paper
Special Issue: Applications of Advanced Technologies in Transportation
Abstract: Dilemma zone (DZ) is an area where drivers can neither stop comfortably nor cross safely when they are presented with a yellow indication at an intersection. The DZ problem is a leading cause for crashes at high-speed signalized intersections. Researchers traditionally assume that vehicles in DZ are equally hazardous and therefore they use the number of vehicles in DZ as an indicator of safety. There is, however, a general understanding among researchers that a DZ-associated accident potential (dilemma hazard thereafter) will vary depending on the subject vehicle’s position and speed at the yellow onset. Based on the previous studies on drivers’ response to the yellow onset, vehicle kinematics, and a Monte Carlo simulation framework, we present a dilemma hazard model for vehicles in the DZ. In light of this model, each vehicle in DZ is assigned a hazard weight according to its position and speed when the yellow is presented. The proposed model is calibrated and validated using the vehicle trajectory data collected at a high-speed signalized intersection in Christiansburg, Va. Finally, the dilemma hazard model is used to obtain optimal clearance interval for the study site.

ASCE Subject Headings:
Stochastic processes
Traffic signals
Traffic safety
Monte Carlo method

Author Keywords:
Dilemma zone
Signal control
Monte Carlo simulation