Evaluation of Pre-emption and Transition Strategies for Northern Virginia Smart Traffic Signal Systems (NVSTSS)

About the report:

Modern traffic signal control systems provide emergency vehicle preemption (EVP) capabilities by utilizing advanced sensors and communication technologies. EVP strategies are widely implemented by urban transportation management agencies. One of the challenges of implementing EVP under coordinated-actuated signal systems is selecting the best coordination recovery strategy at the end of preemption such that disruptions to the normal traffic signal operations are minimized. Similarly, time-of-day (TOD) traffic operations also produce such disruptions while transitioning between TOD modes and require returning to coordination. This report presents the evaluation results of various EVP recovery and TOD transition strategies in an urban corridor including four coordinated-actuated signals along Lee Jackson Memorial Highway in Chantilly, Virginia. Since field testing of various preemption and TOD transition strategies is impractical, the study was performed using hardware-in-the-loop simulation, which consisted of a well-calibrated VISSIM microscopic simulation model, four traffic controllers, and four controller interface devices. The study results showed that advanced controllers (e.g., 2070 and ASC/3) have advantages over the 170 controller for the EVP recovery strategies, while the 170 controller's TOD transition strategies outperformed those of the newer controllers.

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