A framework for the development of bus service reliability measures

Reliability of transit service has been recognized as a significant determinant of quality of service. Numerous indicators have been proposed by individual operational organizations and the research community dependent on specific objectives and resource constraints. Buffer time based indicators are highly desirable since they enable evaluation of the reliability impacts on passengers from an operational approach. However, buffer time indicators can underestimate passengers perceived reliability performance and hide the sources of observed changes in reliability if the buffer time is based on the total travel time distribution. Large samples of disaggregated data, benefiting from Automatic Vehicle Location (AVL) system, provide great potential to measure reliability at very high levels of resolution. The paper proposes a buffer time concept based reliability measurement framework using AVL data, which can disaggregate service performance to a high level of detail. The framework working procedure is illustrated in the case of AVL data from Brisbane. Three example indicators for applications of reliability assessment (operators), journey planning (passenger) and value of time (agencies) are developed to fulfil different stakeholders' requirements.