Mitigating Bus Bunching via Bus Substitution in Modular Vehicle Systems

Bus bunching, where buses arrive at stops in quick succession rather than at evenly spaced intervals, disrupts public transit systems by increasing passenger waiting times and decreasing system reliability. To address this issue, we propose a novel strategy featuring automated modular bus units that can either operate individually or be combined en route to form a larger bus. Our strategy systematically combines this new modular technology with bus bunching mitigation techniques, including stop skipping and bus substitution, to minimize passenger waiting times and operational costs. Our strategy is formulated as a Markov Decision Process and solved by an Advantage Actor-Critic algorithm. Our approach is validated through numerical experiments using real-world data, demonstrating significant improvements in system reliability and passenger satisfaction in various traffic conditions.