Driving Behavior Modeling using Naturalistic Human Driving Data with Inverse Reinforcement Learning

Driving behavior modeling is of great importance for designing safe, smart, and personalized autonomous driving systems. In this paper, an internal reward function-based driving model that emulates the human's internal decision-making mechanism is utilized. To infer the reward function from naturalistic human driving data, we propose a structural assumption about human driving behavior that focuses on discrete latent driving intentions. It converts the continuous behavior modeling problem to a discrete setting and thus makes maximum entropy inverse reinforcement learning (IRL) tractable to learn reward functions. Specifically, a polynomial trajectory sampler is adopted to generate candidate trajectories considering high-level intentions and approximate the partition function in the maximum entropy IRL framework, and an environment model considering interactive behaviors among the ego and surrounding vehicles is built to better estimate the generated trajectories. The proposed method is applied to learn personalized reward functions for individual human drivers from the NGSIM highway dataset. The qualitative results demonstrate that the learned reward function is able to explicitly express the preferences of different drivers and interpret their decisions. The quantitative results reveal that the learned reward function is robust, which is manifested by only a marginal decline in proximity to the human driving trajectories when applying the reward function in the testing conditions. For the testing performance, the personalized modeling method outperforms the general modeling approach, reducing the modeling errors in human likeness (a custom metric to gauge accuracy) by 23%, and these two methods deliver better results compared to other baseline methods.