Repositioning Strategy for Ride-Hailing Vehicles Based on Geometric Road Network Structure and Reinforcement Learning

The inefficient and inaccurate bidirectional search by both ride-hailing drivers and passengers leads to a mismatch between supply and demand. Ride-hailing vehicle repositioning strategy can pre-dispatch vehicles to areas with future demand, improving supply-demand matching. However, existing research mostly uses network grids to represent the urban road environment, lacking geometric topological information and reducing the dispatch accuracy. To address this issue, a ride-hailing vehicle relocation algorithm called GA2C was proposed based on Graph Neural Networks (GNN) and Actor-Critic reinforcement learning algorithm. This algorithm has a smoother learning process and can perform high-dimensional sampling, and it is suitable for learning the best relocation strategy for a large number of ride-hailing vehicles as multi-agent systems. Moreover, the geometric network structure was used to represent the urban road environment by using a GNN as a function approximator to learn the geometric information of the road network. Additionally, an action sampling strategy based on action value function was introduced to increase the randomness of action selection, effectively preventing competition. A ride-hailing vehicle relocation simulation experiment was conducted using Python, and the results are as follows: (ⅰ) the order response rate of the GA2C algorithm is 84.2%, significantly higher than all the comparative experimental results; (ⅱ) in the order distribution comparative experiment, GA2C’s relative improvements in uniform distribution, central distribution layout, block distribution layout, and checkerboard distribution layout are 1.17%, 6.02%, 13.12%, and 14.55%, respectively. The above experimental results demonstrate that the GA2C algorithm can effectively relocate ride-hailing vehicles. When the order distribution presents significant differences, and the distance between different demand areas is relatively close, it can better learn dynamic demand changes, and achieve maximum order response rate by relocating ride-hailing vehicles.