Acting engineer of operations Aaron Weatherholt writes, "Microwave based non-intrusive, dynamic dilemma zone protection is a promising technology to improve safety at the high speed approaches of signalized intersections."

October 21, 2009

LINDON, UT—The Illinois Department of Transportation has approved the use of SmartSensor Advance in that state, based on results of a study conducted last year by Bradley University. In a memo dated October 5, 2009, acting engineer of operations Aaron Weatherholt writes, "Microwave based non-intrusive, dynamic dilemma zone protection is a promising technology to improve safety at the high speed approaches of signalized intersections."

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Protection of the dilemma zone has become a priority for DOTs across the country. The dilemma zone is an area approximately two to five seconds from the intersection stop bar in which drivers must decide whether to stop or go when the light turns yellow; the dilemma becomes more pronounced at high speed approaches with speeds of 45 miles per hour or greater.

Dilemma zone protection systems monitor the approaches and will only allow the green light to terminate when no vehicles are detected in the dilemma zone.

Unlike loops, which can only provide static protection based on "snapshots" of data at fixed locations, SmartSensor Advance uses Digital Wave Radar to continuously track the speed and distance of each vehicle detected within its field of view, and it uses this information to determine each vehicle's estimated time of arrival at the stop bar; the green light is extended until SmartSensor Advance no longer detects any vehicles in the dilemma zone.

Bradley University evaluated SmartSensor Advance at a high-speed, signalized intersection and found that it reduced red light running by 60 percent and yellow light running by 75 percent, compared to loops. "It is expected that these reductions will translate into reductions in red light running crashes and injuries, thus improving safety at the study intersection."

Other states are also discovering the benefits of dynamic dilemma zone protection. Recently, the Pennsylvania DOT approved SmartSensor Advance for use in that state; in Ohio, not only has SmartSensor Advance been approved, it has also been added to Ohio DOT's engineering manual.

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