Modeling and measurements of bus service reliability

A new concept for predicting the performance reliability of a bus service is developed and evaluated. Reliability of bus service is defined as the amount of consistency associated with an operational performance measure from day to day. The variability of travel time performance is posited as the best indicator of reliability. Travel time is found to be an accurate and easily collectible performance measure, and data are collected for several steady periods. These are defined as periods in which performance measure characteristics remain relatively unchanged. A beta distribution with predicted parameters r and T is fitted for the bus travel time data, both for peak and off-peak situations. Based on this distribution, a strategy for predicting perfomance reliability is suggested.