A. Abdelfatah

SYSTEM OPTIMAL TIME-DEPENDENT PATH ASSIGNMENT AND SIGNAL TIMING IN TRAFFIC NETWORK

Optimization of system performance in congested traffic networks is one of the main goals of intelligent transportation systems. A formulation and solution algorithm for the combined signal control and dynamic traffic assignment problem is presented. The solution algorithm is implemented and tested on an actual network, illustrating the benefits that could be attained through joint optimization of signal control and route guidance decisions.

Real-time dynamic traffic assignment and path-based signal coordination: Application to network traffic management

As an example of integrating signal control with network traffic assignment, the notion of path-based signal coordination in transportation networks is introduced and illustrated. The use of a real-time dynamic traffic assignment system allows prediction of the traffic flow patterns and identification of the dominant paths in the network. The signalized intersections along these paths, which may consist of combinations of straight sections and turning movements, are coordinated to increase the capacity of the freeway and the surface street system to efficiently absorb diverted traffic from the freeway. A set of experiments is designed to compare the network performance under the path-based coordination scheme with no coordination and arterial-based coordination. The experiments are conducted for both pretimed and vehicle-actuated signal control. An actual network, which represents the south-central part of the Fort Worth area, is used in these experiments. The network consists of a freeway (I-35W) surrounded by a street network with a total of 178 nodes and 441 arcs. The path-based coordination scheme is shown to outperform arterial-based coordination in the cases of both pretimed fixed control and vehicle-actuated signal control. A significant reduction in the network average travel time under the path-based coordination scheme is observed compared with the other schemes. This application further illustrates the benefits of real-time dynamic traffic assignment for advanced traffic management under incident conditions.