Collaborative freight transport service with high-frequency bus transit systems: Optimal bus operation strategies

In the presence of a rapidly growing demand for urban delivery, existing bus services are recommended to offer collaborative freight transport services, especially during off-peak hours when the bus service capacity is excessive for passenger transportation. While the impact of freight transport on the transit service quality has not been explicitly considered in the literature on the topic of collaborative freight transport, this study aims to investigate, from a bus operator’s perspective, how to determine the optimal bus operation strategies to ensure the freight transport demand can be met while a certain level of bus passenger transport service quality is maintained. A mathematical programming approach is applied to formulate the problem, with the objective of minimizing both the operator’s costs, consisting of the bus operation costs and penalty imposed from unsatisfied freight transport demand, and users’ costs focusing primarily on the passengers’ travel time costs. The main bus operation strategies include bus vehicle seating capacity, fleet size, and bus headway, to be optimized to achieve the objective from the operator’s perspective. A generalized Benders decomposition-based solution algorithm is developed to solve the formulated problem efficiently, with completed algorithmic convergence proof. Numerical experiments are carried out to validate the model formulation and solution efficiency. Some of the numerical results indicate a tendency for bus headway to be set longer, leading to longer waiting times, and lower service quality for passenger transport, especially when freight transport demand is high. This highlights the importance of this study in offering bus service operators analysis tools in managing the trade-off between supplying freight transport service and the compromised passenger transport service quality.