The Urban Challenge [1] was an autonomous vehicle competition sponsored by the U.S. Defense Advanced Research Projects Agency (DARPA) in November 2007. Contestant robots were required to autonomously execute a series of navigation missions through a simplified urban environment consisting of roads, intersections, and parking lots while obeying road rules and interacting safely and correctly with other traffic. In contrast to previous DARPA challenges, which focused on rough-terrain navigation [2], [3], this competition required a system capable of complex autonomous behaviors, such as waiting for precedence at an intersection or passing a slow-moving vehicle on a multilane road.