Operational Evaluation of Detection-Control System, A Dilemma Zone Protection Technology

Detection-Control System (D-CS), a dilemma-zone protection technology developed by the Texas Transportation Institute (TTI) for isolated rural high-speed intersections, was evaluated in a before and after study. By detecting vehicle lengths and speeds at locations 800 ft to 1000 ft (244 m to 305 m) upstream of the intersection; D-CS monitors the approaching vehicles on a lane-by-lane basis and assigns different weights to trucks and cars based on vehicle length. When processing the real time traffic data, D-CS predicts the best time to end the major approach green phase. This paper looks at eight sites in four states for which the United States Federal Highway Administration (FHWA) deployed D-CS. At each site, one week's worth of cycle-by-cycle traffic and video data were collected to assess the effectiveness of D-CS. The analysis results showed that on average, after activation of the D-CS technology, the frequencies of red-light violations, max-outs, and number of vehicles trapped in dilemma zone were reduced by 68%, 9%, and 57% respectively. Based on the results obtained, the research team concluded that larger scale deployment of this technology can improve safety of thousands of signalized intersections that have the desired geometric and traffic conditions under which D-CS is expected to yield a high benefit to cost ratio.