Dispatch of autonomous vehicles for taxi services: A deep reinforcement learning approach

• Published in: Transportation research. Part C, Emerging technologies Vol. 115; p. 102626
• Main Authors: Mao, Chao, Liu, Yulin, Shen, Zuo-Jun (Max)
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2020
• Subjects: Actor-critic algorithm; Autonomous vehicles; Deep reinforcement learning; Demand rebalancing; Policy-gradient; Ride sharing; Taxi dispatching; Taxi dispatching; Deep reinforcement learning; Demand rebalancing; Policy-gradient; Actor-critic algorithm; Autonomous vehicles; Ride sharing
• ISSN: 0968-090X; 1879-2359
• DOI: 10.1016/j.trc.2020.102626

In this paper, we define and investigate a novel model-free deep reinforcement learning framework to solve the taxi dispatch problem. The framework can be used to redistribute vehicles when the travel demand and taxi supply is either spatially or temporally imbalanced in a transportation network. While previous works mostly focus on using model-based methods, the goal of this paper is to explore the policy-based deep reinforcement learning algorithm as a model-free method to optimize the rebalancing strategy. In particular, we propose an actor-critic algorithm with feed-forward neural networks as approximations of both policy and value functions, where the policy function provides the optimal dispatch strategy and the value function estimates the expected costs at each time stamp. Our numerical studies show that the algorithm converges to the theoretical upper bound with less than 4% optimality gap, whether the system dynamics are deterministic or stochastic. We also investigate the scenario where we consider user priority and fairness, and the results indicate that our learned policy is capable of producing a superior strategy that balances equity, cancellation, and level of service when user priority is considered.