APPLICATION OF TRAVEL TIME RELIABILITY FOR PERFORMANCE ORIENTED OPERATIONAL PLANNING OF EXPRESSWAYS

摘要

Evaluation of impacts of congestion improvement schemes on travel time reliability is very significant nfor road authorities since travel time reliability represents operational performance of expressway seg-nments. In this paper, a methodology is presented to estimate travel time reliability prior to implementation nof congestion relief schemes based on travel time variation modeling as a function of demand, capacity, nweather conditions and road accidents. For subject expressway segments, traffic conditions are modeled nover a whole year considering demand and capacity as random variables. Patterns of demand and capacity nare generated for each five minute interval by applying Monte-Carlo simulation technique, and accidents nare randomly generated based on a model that links accident rate to traffic conditions. A whole year anal-nysis is performed by comparing demand and available capacity for each scenario and queue length is es-ntimated through shockwave analysis for each time interval. Travel times are estimated from refined nspeed-flow relationships developed for intercity expressways and buffer time index is estimated conse-nquently as a measure of travel time reliability. For validation, estimated reliability indices are compared nwith measured values from empirical data, and it is shown that the proposed method is suitable for opera-ntional evaluation and planning purposes.