Design and Predeployment Assessment of an Integrated Intersection Dilemma Zone Protection System

Abstract

Despite the fact that both traffic researchers and highway agencies have devoted considerable efforts over the past few decades to improving intersection safety, the development of effective strategies remains a challenging task. This research presents an integrated dilemma zone protection system (DZPS) for contending with the safety issues caused by the presence of a dilemma zone, a primary factor contributing to the rear-end collisions or side-angle crashes at intersections, especially at those experiencing high-speed traffic flows. The entire paper includes three parts: (1) development of an integrated system for protecting vehicles within the dilemma zone; (2) procedures to calibrate those key system parameters with field data at a candidate intersection; and (3) design of a per-deployment assessment process for evaluating such a design prior to its field deployment. The proposed DZPS, developed with a target intersection’s traffic characteristic data and geometric constraints, consists of three principal modules: variable message sign (VMS) for advanced warning or speed display, wide-range sensors to track individual vehicles in the dilemma zone, and a decision module to execute the all-red extension function. Based on a proactive design notion, the proposed DZPS can first use the VMS to inform the approaching drivers of a yellow or red phase ahead and prepare to stop, or to display the speed of the discharging traffic flows from the stop line during a green phase. The information will help compliant drivers to adjust their speeds in a timely manner so as to avoid rear-end collisions. For those aggressive/noncompliant vehicles, the DZPS system’s wide-range sensors will track the evolution of their speeds and locations within the dilemma zone at the interval of every 0.1 s, and then determine whether or not an all-red extension call shall be granted to prevent such vehicles from incurring potential side-angled crashes with vehicles from the side street. Recognizing that reliable evaluation of a deployed DZPS’s effectiveness needs the field data over a sufficiently long period, this study has presented the process for conducting a predeployment assessment with well-calibrated simulation experiments. The effectiveness of the proposed system, demonstrated with the results of the case study at the intersection of highway U.S. 301 at Croom Station Road, Upper Marlboro, Maryland, has also been summarized in this paper. Overall, the proposed system, from both the proactive and reactive perspectives to protect drivers, exhibits quite promising properties for use in practice.