Radar-based dilemma zone protection systems reduced red-light running by up to 80 percent at test locations in Virginia.

Development of evaluation guidelines and comparisons of dilemma zone protection systems.

April 2017
Statewide; Virginia; United States

Summary Information

Nearly half of all crashes in the United States occur at intersections and many of these occur because of red-light runners. This study developed guidelines to evaluate different dilemma zone (DZ) protection methods and applied them to assist engineers at the Virginia Department of Transportation in selecting the best DZ-protection method to reduce red-light running. Dilemma zones are areas where when a traffic signal turns yellow some drivers will proceed and others will stop. Minimizing the number of vehicles in a DZ when a signal turns yellow helps reduce the opportunity to make unsafe decisions.


Eight tasks were completed to achieve the study objectives: 1) literature review and documentation of past experience with DZ protection; 2) data collection site selection; 3) develop a field data collection system; 4) instrument field sites and collect both before and after data; 5) analyze data; 6) develop simulation optimization platform for DZ protection systems; 7) compare performance of different DZ protection systems; and 8) develop general guidelines for selecting DZ protection systems.


Radar-based systems were found to provide the most protection because it can continuously monitor vehicle speeds and act accordingly. Before and after comparisons of red-light running indicated a significant reduction in red-light running (reduced by up to 80 percent) when the radar-based system was activated.

When there are line-of-sight limitations, multi-detector systems are suggested instead of radar-based systems. Green hold/termination systems are contraindicated at volumes greater than 1,200 vehicles per hour because it cannot account for queue backups.

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Addressing Dilemma Zone Issues With Control Solutions

Author: Abbas, Montasir M. et al.

Published By: Virginia Department of Transportation

Source Date: April 2017



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coordinated signals, signal coordination, centralized signal control, signal synchronization, traffic signals, advanced signal control, signal timing optimization, coordinated signal control, advanced signal controller, traffic signal retiming, retiming, dilemma zones, signal timing, radar, detectors, optimization, arterial management

Benefit ID: 2018-01265