The 2007 Urban Challenge, hosted by the U.S. Defense Advanced Research Projects Agency (DARPA), featured autonomous vehicle technology in an urban environment. This paper presents the route planning module for the vehicle developed by the Ohio State University Autonomous City Transport (OSU-ACT) team. Based on given information of the urban road network, this module is able to search for optimal routes to direct the vehicle through a series of checkpoints. It is also capable of dealing with dynamically changing road networks, through real time re-planning with updated road information. Simulations and field tests have validated the performance of the route planner.