Corner case generation is crucial for the safety evaluation of highway automated vehicles (HAVs).  Existing studies have not considered the systematic generation of corner cases for interactive driving scenarios like highway ramp merging or roundabouts entering. We propose an ambiguity-guided adversarial behavior planning algorithm to generate confusing behavior for the primary other road user (PORU) in interactive scenarios. The PORU is modeled as a cost-minimizing agent with hierarchical intentions. The adversarial PORU plans actions to confuse the HAVs by maximizing the ambiguity with respect to its intentions, while also taking nominal behavior planning goals into consideration. Two interactive scenarios are studied: highway merging and pedestrian crossing. A corner case testing scheme is designed and implemented for both scenarios to evaluate the performance of different HAVs comprehensively and objectively.

A highly automated vehicle (HAV) is a safety-critical system. Therefore, a verification and validation (V&V) process that rigorously evaluates the safety of HAVs is necessary before their release to the market. In this paper, we propose an interaction-aware safety evaluation framework for the HAV and apply it to the roundabout entering, a highly interactive driving scenario with various traffic situations. Instead of assuming that the primary other vehicles (POVs) take predetermined maneuvers, we model the POVs as game-theoretic agents. To capture a wide variety of interactions between the POVs and the vehicle under test (VUT), we use level-k game theory and social value orientation to characterize the interactive behaviors and train a diverse library of POVs using reinforcement learning. The game-theoretic library, together with initial conditions, form a rich testing space for the two-POV roundabout scenario. On the other hand, we propose an adaptive test case generation scheme based on adaptive sampling and stochastic optimization to efficiently generate customized challenging cases for the VUT from the testing space. In simulations, the proposed testing space design captured a wide range of interactive situations at the roundabout scenario. The proposed test case generation scheme was found to cover the failure modes of the VUT more effectively compared to other test case generation approaches.