Accuracy of travel time necessary for DRGS and evaluation of measuring algorithm

摘要

The dynamic route guidance system (DRGS) using real- time, dynamic information has been identified as a necessity for alleviating today's chronic traffic congestion. Current traffic information, and accurately determining and predictingtravel time data in particular, are important factors directly affecting DRGS viability. The effect of the estimated (current) link travel time precision on DRGS performance, and the conditions for practical DRGS implementation, were thereforeevaluated. It was determined that to effectively provide optimum route guidance and travel time information, major DRGS functions, the estimation precision of the link travel time must be a fair estimation within 10% of the actual travel time, andprediction precision must be a fair estimation with a maximum 25% margin of error for destinations 90 minutes ahead. An intelligent travel time prediction method executed by the on- board system was therefore studied and evaluated. This method wasshown to accurately measure the travel time for approximately 90% of all links during normal travel, thus virtually eliminating abnormal travel and providing sufficient practical performance.