An assessment of alternative bus reliability indicators

Abstract

This paper has reviewed operationally based statistics with seven other indicators of urban bus service reliability using an assessment framework and an assembly of evidence drawn from a study undertaken for the NSW Independent Transport Safety and Reliability Regulator (ITSRR) in 2006. The original 2006 review concluded that excess waiting time (EWT) was the preferred measure for high frequency bus services with the percentage of buses running on-time the preferred indicator for low frequency services with little to choose between measuring arrival versus departure times. This paper has updated the 2006 review to take account of developments in the automatic collection of travel time data on buses and trains. For rail in Sydney, the incorporation of control systems that record the time of day at which trains are at stations has enabled a new measure of customer journey time delay (CJTD) to be developed that incorporates lat stationr and lon trainr delays and can be calculated for both frequent and infrequent services. When considered alongside the other nine reliability indicators, the new CJTD measure ranked equal top with EWT. Both measures were considered easy to understand and have a high customer focus. Where they differed was in terms of fidelity/objectivity and cost efficiency. However with automatic collection of travel times, CJTD should become a practically feasible measure for bus as has already been demonstrated for rail in Sydney.