Local synchronization control scheme for congested interchange areas in freeway corridor

Congestion that initiates at closely spaced highway junctions and intersections, particularly freeway interchange areas, may spread and severely degrade the operational efficiency of the whole network if not handled in a timely and proper manner. A local synchronization traffic control scheme is proposed to manage queues at those critical locations through coordination of neighboring intersection traffic signals and freeway onramp meters. By reducing the amount of traffic feeding into and increasing the amount of traffic discharging from heavily queued sections, the scheme can prevent a queue from evolving into gridlock and thus improve overall system performance. With the help of a network kinematic wave traffic flow model, the local synchronization scheme is implemented and tested on a computer for two sample networks, one small synthetic corridor network and one large, real corridor network. The numerical results indicate that this control scheme can improve the overall operational efficiency in both corridors considerably, with as much as 50% travel time savings. This control scheme appears to perform best under incident conditions and, somewhat surprisingly, compares favorably with a more complex global optimal control scheme.