  Within a robot autonomy stack, the planner and controller are typically
designed separately, and serve different purposes. As such, there is often a
diffusion of responsibilities when it comes to ensuring safety for the robot.
We propose that a planner and controller should share the same interpretation
of safety but apply this knowledge in a different yet complementary way. To
achieve this, we use Hamilton-Jacobi (HJ) reachability theory at the planning
level to provide the robot planner with the foresight to avoid entering regions
with possible inevitable collision. However, this alone does not guarantee
safety. In conjunction with this HJ reachability-infused planner, we propose a
minimally-interventional multi-agent safety-preserving controller also derived
via HJ-reachability theory. The safety controller maintains safety for the
robot without unduly impacting planner performance. We demonstrate the benefits
of our proposed approach in a multi-agent highway scenario where a robot car is
rewarded to navigate through traffic as fast as possible, and we show that our
approach provides strong safety assurances yet achieves the highest performance
compared to other safety controllers.
