Electronic traffic controls

Implementation of the Optimized Policies for Adaptive Control (OPAC) strategy in conjunction with a vehicle velocity controller offers the potential for significantly improving the control strategies used at isolated intersections with respect to measured vehicle delays. The exhaustive sequential search procedure by OPAC provides the optimal switching policies for the intersection while the vehicle velocity controller varies vehicle velocities to reduce vehicle stopping delays. The OPAC algorithm implemented with the vehicle velocity controller was found to have substantially lower delays than OPAC alone.

The goal of this research is to answer a single question. During an urban evacuation, is it advisable for regional planners to allow transit units signal priority in cases where police assisted traffic controls are not an option? Standard practice for emergency evacuation is to place police officers at intersection throughout the evacuation area. However, this is not always an option where environmental factors such as the presence of fire, chemical plume, radioactive fallout (nuclear contaminated wind and dust) do not permit police presence. Results from a case study conducted on Washington D.C. show that it would take four non-prioritized transit units to accomplish the same task as three prioritized vehicles. Furthermore, allowing transit signal priority during an urban evacuation has little to no effect on evacuation clearance time or evacuee travel time. Moreover, when transit signal priority is restricted to operate only on evacuation routes, evacuee travel and delay time decreases.