PTV Mobility News – January 2024

Jan 19, 2024 | News
3 Min Read

New Hardware and Software Technologies Proving Essential in More Effective, Real-Time Strategies for Dilemma Zone Protection

As advances in technology are having a positive impact on roadway safety and efficiencies, one of the critical areas that continues to be a safety concern is the “dilemma zone.” According to Gazis, Herman, and Maradudin’s original 1960s dilemma zone research, The Problem of the Amber Signal Light in Traffic Flow, a dilemma zone is defined as the area in which a driver is unable to stop safely before the stop bar, or proceed through the intersection before the signal turns red. Today, this is what is known as the “Type I” dilemma zone. In the 1970s, further research by Charles V. Zegeer and Deen, Green-Extension Systems at High-Speed Intersections, considered distances relative to vehicle velocity and driver behavior. This is known as the “Type II” dilemma zone and is often referred to as the “indecision zone.” The Type II dilemma zone consists of the area in which a driver decides to either stop or proceed through the intersection before the signal turns red.

The Type II dilemma zone is the distance beyond which 90 percent of all drivers would stop if presented with a yellow signal, or about five seconds of travel time. This zone is the most critical point in ensuring the safe passage of all roadway users at or approaching the intersection. The zone itself consists of the area between a “likely stop” decision versus a “likely go” decision made by each driver faced with a green or yellow signal indication.

Fortunately, new sensorcontroller, and software technologies are providing instantaneous geo-positional vehicle information. This real-time data is proving essential in implementing new strategies for dilemma zone protection, effectively addressing the critical “indecision zone.” We now have the ability to leverage high-resolution sensor data with vehicle tracking and new traffic controller software to dynamically apply signal timing changes, like extending green-light and all-red-light timing in real-time to reduce collisions and serious injuries at intersections.

In addition, the real-time geo-positional vehicle data that new hardware and software technologies are now providing can have a profound impact on mobility beyond dilemma zone safety. By combining real-time data with modeling and simulation, real-time intersection control and signal optimization strategies for dynamic traffic management can be applied throughout a transportation network, helping make Vision Zero a reality.

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