Bus Signal Priority Solution for Non-Uniform Vehicle Arrival Conditions

Bus signal priority (BSP) is an affordable and less infrastructure-demanding operational strategy that is used to improve the efficiency and reliability of transit vehicles. Majority of the studies on BSP are designed with the assumption of uniform vehicle arrivals and departures, ignoring the intra-cycle and inter-cycle traffic variations. However, real-world situations frequently involve fluctuations in the number of vehicle arrivals from one signal cycle to the next or within a cycle, which the available solutions cannot handle easily. This study addresses this using an analytical solution based on the incremental queue accumulation (IQA) method for BSP with two signal controller actions, i.e. red truncation (RT) and green extension (GE). The basic objective of the proposed solution is to minimize the total person delay at the intersection, considering all vehicles in all approaches. The solution was evaluated by integrating it with VISSIM and compared for both intra-cycle and inter-cycle flow variations for three scenarios: using basic Webster equation, using Webster’s random delay term for non-uniform arrivals, and using the IQA method for non-uniform arrivals. The results showed that the proposed solution using the IQA method outperformed both in terms of overall person delay reduction and increase in the percentage of priority provided.