Evaluation of system-wide traffic signal control using stochastic optimization and neural networks

The problem of system-wide traffic control is one of the most challenging in advanced traffic management. The S-TRAC (system-wide traffic-adaptive control) method was introduced as a means for producing optimal real-time signal timings on a system (network)-wide basis. S-TRAC has several desirable features that make it both practically feasible and theoretically sound in addressing the system-wide control problem. Among these features are: (1) no system-wide traffic flow model is required; (2) S-TRAC automatically adapts to long-term changes in the system (e.g., seasonal variations) while providing real-time responsive signal commands; and (3) S-TRAC is able to work with existing hardware and sensor configurations within the network of interest (although additional sensors may help the overall control capability). The Montgomery County (Maryland) Department of Public Work and Transportation and JHU/APL have collaborated in moving towards a possible field demonstration of S-TRAC in a moderately congested network. The paper presents an innovative measure-of-effectiveness that evaluates the interruptions of the traffic flow caused by the traffic signal and also reflects the needs of traffic engineers in Montgomery County, Maryland. Also, the paper describes some of the practical implementation issues that have been addressed and presents the results of some realistic simulations built from Montgomery County traffic data.