Collaborative optimization of vehicle scheduling and speed regulation for autonomous customized bus systems

Abstract

Customized bus systems can improve service quality and efficiency by taking advantage of the speed regulation and capacity variation of autonomous bus systems. To address the challenges of customized bus systems design, this study proposes a collaborative optimization model of vehicle scheduling and speed regulation for the autonomous customized bus system. This model minimizes enterprise operation and passenger travel costs by considering mileage constraints, the time window of passenger travel constraints, and demand pairs coverage constraints. Based on the theoretical properties discovered in the joint design model, the problem is decomposed into a set partitioning master problem and route-selection subproblem. An algorithm combining column generation approach and genetic algorithm is proposed to solve the joint design model. To accelerate the calculation in searching for the shortest route for subproblems, hierarchical filtering strategy is used to reduce the cost of finding feasible routes and improve computational efficiency. The case study reveals that the proposed algorithm exhibits better convergence and stability according to the Wilcoxon test. In a numerical experiment with 100 demand pairs, the joint model can be solved by the algorithm proposed in the study optimally with 19% of the computation time required by the exact algorithms. The departure frequency was reduced by 22%, and the operating cost was reduced by 42% compared with those of customized bus lines serviced separately by human-driven buses. Sensitivity analyses were performed on various operating parameters, such as modular bus capacity and speed boundary, across three different scale cases. The results demonstrate that reasonable parameter settings are beneficial for reducing operating costs and vacant seats.