Comparison of Emergency Vehicle Preemption methods using a Hardware-In-The-Loop simulation

Abstract

Modern traffic signal control systems provide Emergency Vehicle Preemption (EVP), which provides the right-of-way to emergency vehicles in preference to other vehicles. Traffic engineers should select the best coordination recovery strategy at the end of the preemption in order to minimize any resulting disruptions. This paper compares the various EVP methods available with a controller used in the USA. The comparison was conducted in an urban corridor including four coordinated-actuated signals using a Hardware-In-the-Loop Simulation (HILS), which consisted of a well-calibrated VISSIM microscopic simulation model and four Type 170 controllers. The examined preemption strategies included shortway and dwell with different numbers of cycles for transition completion. The results of the comparison indicated that the resulting impact on the network-wide and intersection-specific performances varied with the selected EVP method. The results also indicated that the EVP function using a shortway transition method with two or three cycles worked the best, as it could minimize the impacts of EVP.