Drivers’ actions in an intersection’s dilemma zone – the area where the decision to stop at a yellow light or continue through it is not clear-cut – can lead to side-angle and rear-end crashes. In Maryland, researchers developed an intelligent dilemma zone protection system (DZPS) that is reducing these crashes by anticipating drivers’ decisions and responding. The DZPS system was deployed at two high-speed rural intersections (US 40@Western Maryland Parkway and MD 213@Williams/Locust Point Road), and it has three components:
(1) two wide-range sensors to track the speeds and locations of all vehicles within the identified dilemma zones;
(2) software to predict the response of drivers during the yellow phase and to activate the all-red extension function if needed; and
(3) a web-based module for responsible engineers/technicians to monitor the system’s performance from a control center.
Measured benefits of DZPS include a 30 to 40 percent reduction in dilemma zone length and fewer vehicles approaching the intersection at speeds greater than the posted speed limit. The all-red extensions have helped prevent crashes between through traffic and vehicles entering the intersection from the cross street.