Inconsistency of Optimal Signal Timing Plans at Design and Evaluation Stages in ITS Management

This paper brings discussion on the discrepancy between optimal signal timings at design and evaluation stages in the ITS traffic management. Evaluation methods of signal timing design software used in many consulting firms differ from the one of the HCM, a prescribed evaluation method required at the final decision making stage in most states. If such a difference exists, it would falsely guide the correct design alternative to failure and thus increase the social costs. In this study, traffic signal timings suggested by TRANSYT and SOAP were compared with the HCM optimums searched through a hybrid genetic algorithm. It was found that such differences truly exist and a new method is necessary to keep the potential alternatives as the options available from being withdrawn.