Local and Iterative Searches for Combined Signal Control and Assignment Problem Implementation and Numerical Examples

摘要

Traffic signal-setting policies and traffic assignment procedures are mutually dependent. The combined signal control and traffic assignment problem deals with this interaction. With the total travel time minimization objective, gradient-based local search methods are implemented. Deterministic user equilibrium is the selected user route choice rule, Webster's delay curve is the link performance function, and green-time-per-cycle ratios are decision variables. Three solution codes are implemented, resulting in six variations. Three solution codes are implemented, resulting in six variations including intersections with multiphase operation and overlapping traffic movements. For referrence, the iterative approach is also coded, and all codes are tested in four example networks at five demand levels, the results show the numerical gradient estimation procedure performs best, although the simplified local searches reduce the large network computational burden. Demand level as well as network size affects the relative performance of the local and iterative approaches. As demand level becomes higher, (a) in the small network, the local search tends to outperform the iterative search, and (b) in the large network, the opposite result is obtained.