Public expectations for automated vehicles span a broad range, from mobility for passengers, to road user safety, to compliance with the traffic code. In most ordinary situations, these expectations can be satisfied simultaneously. But these various expectations can also lead to exceptional scenarios where certain objectives, such as those related to safety, are in tension with road rules. Exceptional driving scenarios challenge motion planning algorithms in automated vehicles to find solutions that are legally grounded, ethically sound, and technically feasible.

The general public’s familiarity with exceptional driving scenarios comes from the classic "Trolley Car" problem in philosophy, asking who should live and who should die in an unavoidable collision. These discussions tend to take a consequentialist view by framing the ethical action as the one that achieves the best outcome. By taking a different perspective that views driving as a social contract, the AV's ethical obligations are limited to meeting the duty of care owed to other road users. With this perspective, the existing legal system in the US provides a framework for choosing appropriate behaviors in exceptional driving cases and for answering the Trolley Car problem. This work outlines principles that prioritize care for humans, respect the authority of human-defined traffic law, and ensure that the vehicle avoids decisions that introduce unreasonable risks. Developing AVs that can legally and ethically negotiate exceptional driving scenarios is simply a matter of translating the principles into engineering requirements with no need for new laws or endless philosophical debate.