Quantifying Dynamic Factors Contributing to Dilemma Zone at High-Speed Signalized Intersections

The issue of the dynamic yellow light dilemma zone (DZ) has been raised by researchers for many years. However, quantitative study of the inherent factors contributing to the dynamic DZ remains an issue, perhaps because of the lack of effective means for collecting the trajectory data. This paper presents an analysis of the dynamic characteristics of major contributing factors for Type I DZ and the option zone on the basis of vehicle trajectory data during yellow intervals. The qualified trajectory data of 1,445 vehicles were extracted from 46-h high-resolution videos shot at four high-speed signalized intersections in Ohio with the use of the cost-effective software VEVID, developed and upgraded by the first two authors. The statistical analysis of the obtained trajectory data quantitatively revealed the dynamic nature of major DZ contributing factors. Results indicated that the minimum perception–reaction time of drivers was greatly influenced by speed and could be modeled as a function of the speed. The maximum deceleration rate for stopping and the maximum acceleration rate for running a yellow light were greatly dependent on speed and the 85th percentile speed of the intersection approach. The rates could be expressed as a function of those two variables. On the basis of the new findings, the traditional Type I DZ model was greatly modified and improved. The new model provides a theoretical base for updating the existing DZ tables with the identified dynamic characteristics of the contributing factors.