Dynamic flashing yellow for emergency evacuation signal timing plan in a corridor
Asamoah, Charles Amoateng
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An effective and efficient signal timing plan for emergency evacuation is very crucial for public safety. Two main objectives of emergency evacuations are to increase throughput on the main street and decrease delay on the side streets. Some studies have proved the effectiveness of the static flashing yellow (SFY) signal timing plan in evacuating high number of vehicles (Chen et al. 2007). However, one disadvantage of the static flashing yellow signal timing plan is the high delay that side street traffic experiences. This thesis investigates a variant of the static flashing yellow signal timing plan called dynamic flashing yellow (DFY) signal plan. The dynamic flashing yellow signal timing plan has two main phases of operation for every signal controller. Phase 1 is flashing yellow on the main street and flashing red on the side street, whereas phase 2 is red signal on main street and green signal on the side street. Three different types of DFY signal timing plan are proposed- Fixed DFY, Actuated DFY and Actuated and Coordinated DFY. This thesis demonstrates that the dynamic flashing yellow provides a high volume of evacuated vehicles with relatively low delay to side street traffic. Also the proposed DFY is adjustable to favor different weights between throughput and delay. A microscopic traffic simulation tool, VISSIM, is used to model and compare several emergency signal timing plans for a real network in Buffalo, NY which is a 4.1 mile corridor. The DFY signal timing plan is compared to PM peak plans and the SFY signal plan. The DFY signal timing plan is further analyzed under different minimal cycle lengths. It is realized that a minimal cycle length of 60s gives the best results (Pareto non-dominated solutions) for the DFY plan.