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

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 predicting travel 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 evaluated. It was determined that to effectively provide optimum route guidance and travel time information, the estimation precision of the link travel time must be within 10% of the actual travel time, and the prediction 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 studied and evaluated. This method was shown 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.