Using Travel Time Reliability Measures to Improve Regional Transportation Planning and Operations

Abstract. Travel time estimation is of increasing importance to travelers and transportation professionals alike as congestion worsens in major urban areas. In fact, the reliability of travel time estimates on a given corridor may be more important for travelers, shippers, and transport managers than the travel time itself. This paper examines the uses of measured travel time reliability indices for improving real-time transportation management and traveler information using archived ITS data. Beginning with a literature review of travel time reliability and its value as a congestion measure, a content analysis of twenty regional transportation plans from across the nation is then described. Results from the content analysis indicate that travel time reliability is not currently used as a congestion measure, and that the most common measures of congestion were the volume-to-capacity ratio, vehicle hours of delay, and mean speed. Then, as a case study using data from Portland, Oregon, several reliability measures ar