Evaluating reliability of TRANSYT-7F optimization schemes

This paper investigates the reliability of TRANSYT-7F optimal solutions fro m two perspectives: (1) the effect of the selected optimization criterion o n the values of various system performance measures; and (2) the extent to which TRANSYT-7F signal plans remain optimal when evaluated in a microscopi c and stochastic traffic environment. The well-established CORSIM model was used for the latter test. A customized code has been developed that can au tomatically generate statistical distributions of selected performance meas ures in CORSIM based on various TRANSYT-7F optimization runs. The method ha s been applied to a calibrated test network in Chicago consisting of 9 sign alized intersections with 50 nodes and 74 links. It was found that while go od correlation existed between the corresponding performance measures in TR ANSYT-7F and CORSIM under light traffic, their correlation diminished under congested flow. In particular, the best signal strategy identified in TRAN SYT-7F was not the best in the CORSIM environment. The discrepancies are un doubtedly due to the basic difference between the two models: TRANSYT-7F is deterministic, CORSIM is stochastic.