A path planning system helps an autonomous surface vessel to navigate autonomously while obeying international maritime law. The Anti-Submarine Warfare (ASW) Continuous Trail Autonomous Vessel (ACTUV) program is building a fast, intelligent autonomous surface vessel. NREC is developing ACTUV’s path planner, the key component of the vessel’s autonomy system. ACTUV can operate autonomously for long periods of time with minimal supervision from shore. It avoids navigation hazards and follows the International Regulations for Preventing Collisions at Sea (COLREGS), which define the “rules of the road” for ships and other ocean-going vessels. NREC is working on the ACTUV program under prime contractor Leidos (formerly SAIC), which is building the vessel. DARPA sponsors the program.