Causal analysis of bus travel time reliability in Birmingham, UK

A reliable public transport system plays an important role in reducing energy consumption, carbon emission, road congestion and increasing urban operating efficiency. However, the reliability of public transport systems in some cities is facing the pressure of population and urban expansion, making it unattractive to passengers and leading to a higher level of car dependency. This paper focuses on Birmingham's bus service reliability and potential factors affecting bus travel delay based on the 63 bus route operational data in Birmingham. This study is conducted by doing data processing, bus travel time distribution analysis and, bus travel time delay causes analysis. For the analysis, models are developed by using Stata software. 12 variables are considered to estimate the bus delay. This study applies a regression technique to develop models. The results of bus travel time distribution analyses show the average bus travel time is behind schedule. The results of regression models show departure delay, number of signalised intersections, number of pedestrian crossing phases, and distance between stops are factors affecting bus travel delay. At the route level, the results show parades and roadworks could increase bus travel time delay while protests and rainfall have no significant effect and road accidents could sometimes impact bus travel time delay. Finally, it is recommended that a tighter bus on-time performance monitoring scheme should be applied to let drivers know the delay status of the bus and safely allow drivers to drive at a higher speed. Transit signal priority (TSP) techniques are also applicable but it needs detectors and traffic signals to be equipped on buses to give priority for buses at the intersection. Lastly, alternative diversion plans can also be provided in case of any predictable and unpredictable road closures. This is for being sent to passengers to assist passengers' decision-making.