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The Urban Challenge 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, 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. These behaviors were managed by a software subsystem called the behavioral executive in Boss, Tartan Racing's winning entry in the Urban Challenge. The fulfillment of this role required the carefully structured integration and management of many disparate capabilities in a highly flexible manner over the course of the development, accommodating whatever changes were necessary to win the competition amidst a continuously evolving software system. These requirements, among many others, are reflected in the behavioral executive's architecture, the flexibility and adaptability of which played an important role in the team's success.