After deployment of a dilemma zone protection system in Maryland, the percentage of vehicles approaching rural intersection sites at excessive speeds dropped from 29 to 16 percent at one site and from 8 to 1 percent at another site.

Improved dilemma zone protection system deployed at two rural intersections in Maryland.

July 2017

Summary Information

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) to reducing these crashes by anticipating drivers’ decisions and responding.


The DPZS system was deployed at two high-speed rural intersections (US-40 at Western Maryland Parkway in Hagerstown, MD and MD-213 at Williams/Locust Point Road in Elkton, MD) and has three components: (1) two wide-range sensors to track 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 engineers/technicians to monitor the system’s performance from a control center. Field evaluations of the deployed DZPS were conducted about one month after the system activation dates, and real-time system monitoring and performance analysis was carried out with respect to the traffic flow characteristics impacts and the all-red extension activations.


After deployment of the dilemma zone protection system, the percentage of vehicles approaching at a speed over 55 mi/h (the posted speed limit) at the intersection of US-40 and Western Maryland Parkway reduced from 29 to 16 percent (measured 900 ft from the stop bar). At the intersection of MD-213 and Williams/Locust Point Rd it dropped from 8 to 1 percent (measured 500 ft from the stop bar).

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Intelligent Dilemma Zone Protection System at High-Speed Intersections

Author: Park, Sun Yoon; and Gang-Len Chang

Published By: Maryland Department of Transportation State Highway Administration

Source Date: July 2017

Other Reference Number: MD-17-SHA/UM/3-32



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Goal Areas


Typical Deployment Locations

Rural Areas


dilemma zone, DZPS, rural, safety, dilemma zone protection system

Benefit ID: 2017-01213