Analytical approach to estimate delay reduction associated with bus priority measures

Bus delay reduction is an essential input to the objective evaluation of the performance of Public Transport Priority (PTP) measures. Functions for estimating bus delay reduction associated with various types of PTP measures can be used to optimise priority and signal control, or used as a planning tool when more expensive simulation is not available. However, existing delay functions for evaluating PTP measures, such as Dedicated Bus Lanes (DBLs) or Transit Signal Priority (TSP), tend to ignore delay associated with bus acceleration. Moreover, there is no study dedicated to developing bus delay functions to evaluate the performance of Queue Jump Lanes (QJLs) or QJLs combined with TSP. This paper proposes delay functions to analytically estimate bus delay effects for a range of PTP measures, including DBLs, QJLs, TSP, TSP combined with QJLs, and TSP combined with DBLs. Kinematic Wave Theory (KWT) is used to estimate queuing delays at traffic signals. Delay associated with bus acceleration is also analytically approximated. The proposed bus delay functions are validated using traffic micro-simulation, which indicates that the proposed functions accurately estimate bus delay effects of the considered PTP measures with small errors.