Transit Service Reliability

Abstract

This report presents a comprehensive overview of the subject of transit service reliability and provides a framework for a program of demonstrations and research studies which could be carried out under the Service and Methods Demonstration program. Major subject areas included the impact of service reliability from the operator's perspective, empirical measures of service reliability, causes of service reliability problems, techniques for improving service reliability, and recommendations for further research. Several findings are reported herein, namely: (1) transit service reliability is a significant determinant of traveler mode and departure time choices; (2) service reliability is crucial in influencing the costs of providing transit service; and (3) current evaluation measures are not able to capture the variety of impacts of service reliability on travel behavior and operator costs. Several proposed measures are recommended herein for use in future evaluation studies. Numerous causes of reliability problems are identified, some which appear to be inherent in the specific transit service concept, and others which are more environmental in nature. A review of previous and current analyses reveals inconclusive findings in determining the relative importance and magnitude of each cause. Several strategies are considered to improve service reliability of fixed route and demand responsive transit systems. These strategies are directed at alleviating the initial cause of unreliability or serve as a corrective measure when the reliability problem has already developed.