In this paper, we propose an autonomous navigation system in urban environments. In order to create a useful navigation system in urban environments, the system examines whether the area near around is traversable or not in real time, instead of using prior knowledge of dense maps. To examine the traversability robustly, the system adopts the following technologies. The system involves a localization with the information of GPS and dead reckoning, and integration method using Divided Difference Filter (DDF). DDF is an appropriate localization method using truncated data of GPS in urban areas. The system also estimates traversability of road regions using a laser range finder (LRF). By estimating traversability, robot is able to run safely on the route even if localization had poor accuracy. Lastly, the system detects moving obstacles using LRF, because the robot must be operated in environments where many people would exist. The effectiveness of the proposed system is proved through some experiments in outdoor environments including various situations. © 2011 IEEE.