  Ensuring safety for human-interactive robotics is important due to the
potential for human injury. The key challenge is defining safety in a way that
accounts for the complex range of human behaviors without modeling the human as
an unconstrained adversary. We propose a novel approach to ensuring safety in
these settings. Our approach focuses on defining backup actions that we believe
human always considers taking to avoid an accident -- e.g., brake to avoid
rear-ending the other agent. Given such a definition, we consider a safety
constraint that guarantees safety as long as the human takes the appropriate
backup actions when necessary to ensure safety. Then, we propose an algorithm
that overrides an arbitrary given controller as needed to ensure that the robot
is safe. We evaluate our approach in a simulated environment, interacting with
both real and simulated humans.
