Relocatable detector concept for dilemma zone protection at high-speed intersections

High-speed intersections can substantially impact the safety of the public and the efficiency of the intersection if not designed properly. Although advance detectors are used to respond to varying traffic demands, most detectors in use today consist of inductive loops permanently placed under the surface of the pavement and located according to the roadway design speed. Because the location and size of a dilemma zone vary depending on traffic and roadway conditions, permanent placement of detectors offers limited dilemma zone protection. This research looks into a relocatable detector concept as an alternative solution to providing dilemma zone protection at high-speed intersections. By obtaining advance speed information during a selected time interval, the system determines the most needed protection zone in real time and simulates detector reposition to the appropriate locations using non-intrusive detection technology. With this design, the intersection not only operates more safely, but also more efficiently because unneeded extensions can be avoided. The effectiveness of the proposed detector concept was demonstrated through testing with field data, where the probability of max-out and the reliability of dilemma Zone protection were analyzed and compared with those of a fixed detector scheme.