PATROL: A Velocity Control Framework for Autonomous Vehicle via Spatial-Temporal Reinforcement Learning

The largest portion of urban congestion is caused by 'phantom' traffic jams, causing significant delay travel time, fuel waste, and air pollution. It frequently occurs in high-density traffics without any obvious signs of accidents or roadworks. The root cause of 'phantom' traffic jams in one-lane traffics is the sudden change in velocity of some vehicles (i.e. harsh driving behavior (HDB)), which may generate a chain reaction with accumulated impact throughout the vehicles along the lane. This paper makes the first attempt to address this notorious problem in a one-lane traffic environment through velocity control of autonomous vehicles. Specifically, we propose a velocity control framework, called PATROL (sPAtial-temporal ReinfOrcement Learning). First, we design a spatial-temporal graph inside the reinforcement learning model to process and extract the information (e.g. velocity and distance difference) of multiple vehicles ahead across several historical time steps in the interactive environment. Then, we propose an attention mechanism to characterize the vehicle interactions and an LSTM structure to understand the vehicles' driving patterns through time. At last, we modify the reward function used in previous velocity control works to enable the autonomous driving agent to predict the HDB of preceding vehicles and smoothly adjust its velocity, which could alleviate the chain reaction caused by HDB. We conduct extensive experiments to demonstrate the effectiveness and superiority of PATROL in alleviating the 'phantom' traffic jam in simulation environments. Further, on the real-world velocity control dataset, our method significantly outperforms the existing methods in terms of driving safety, comfortability, and efficiency.