HMSim: A Hierarchical Multi-Agent Simulator for Autonomous Vehicles

Abstract

This paper addresses the challenge of developing a realistic urban-driving simulator to accurately model agent behaviors, a crucial component for self-driving car development. Most previous simulators focus on the plausibility of sensor data synthesis, whereas the plausibility of driving behaviors is poorly explored. To tackle this problem, we propose a hierarchical architecture, which comprises (i) a high-level intention simulation summarizing driving scenarios and (ii) a low-level policy trained by reinforcement algorithms to refine plans. Unlike existing simulators, our approach captures diverse behaviors, even sub-optimal ones, vital for robust policy training and evaluation. We also highlight the importance of interactive simulations over static scenarios for realistic policy development. Extensive experiments demonstrate that our approach significantly improves long-term behavior prediction and closed-loop simulation, enhancing the realism and diversity of urban-driving simulations. The videos of this work are available in our project page: href{https://sites.google.com/ucsd.edu/h-sim/home}{https:/ /sites.google.com/ucsd.edu/h-sim/home}.