Using Dynamic Flashing Yellow for Traffic Signal Control under Emergency Evacuation

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Using Dynamic Flashing Yellow for Traffic Signal Control under Emergency Evacuation

Asamoah, Charles A. / He, Qing

Effective signal timing plans for emergency evacuation are crucial for public safety. Two conflicting objectives of emergency evacuation in a corridor are to increase throughput on the main street (evacuation route) and to decrease delay on the side streets. Previous studies have proved the effectiveness of using the static flashing yellow signal timing plan in evacuating a high number of vehicles. However, the static flashing yellow plan also yields extremely high delay on side streets. This study investigates a variant of the static flashing yellow plan called the dynamic flashing yellow (DFY) signal timing plan under a few reasonable assumptions. The DFY plan consists of two signal phases. Phase 1 is flashing yellow on the main street and flashing red on the side street, whereas Phase 2 is a red signal on the main street and a green signal on the side street. Three types of DFY plans are proposed, including fixed DFY, actuated DFY, and actuated and coordinated DFY. This study demonstrates that the DFY provides a high volume of evacuated vehicles with relatively lower delay to the side street traffic. Moreover, the DFY is adjustable to favor different weights between network throughput and average delay. To compare the DFY with the static flashing yellow and other plans, VISSIM is implemented to model a 4.1-mi corridor in Buffalo, New York. The DFY plan is further analyzed by method and cycle length. According to the Pareto frontier, the actuated and coordinated DFY with cycle lengths of 60 s and 120 s produces more desirable results (Pareto nondominated solutions) than other plans.