Abstract: GPS is the most widely-used outdoor positioning system. With the advance of relevant technologies, positioning accuracy of GPS has been increasing continuously. However, as the GPS satellite signal can be blocked by buildings, multi-path error becomes the major cause of positioning error in a city. Evaluating the negative effects of GPS error on urban environments, which is referred as environment friendliness in this paper, will help the prediction of GPS error range in different road segments. Furthermore, it enhances user experiences of location-based services, reveals the relationship between environmental characteristics and multi-path error, and helps to determine where to deploy supplementary positioning devices. In this paper, we have proposed an urban road friendliness evaluation (URFE) approach, based on the processing and analyzing of massive historical bus GPS trajectory data. Specifically, URFE first takes full advantage of the unique features of fixed bus routes to significantly improve the efficiency of data processing. Then, it adopts a fault-tolerant method to deal with the possible errors of street maps; Finally, URFE completes the missing data by utilizing the inherent relationship between GPS errors of the same cars and roads, and utilizes an evaluation strategy by taking the influence of different GPS terminal devices’ qualities into account. Using the bus trajectory data within the second ring road of Chengdu during one month, we evaluate the effectiveness of our approach. Environments friendliness of 5648 different road segments has been evaluated, whose rationality has been verified by checking real satellite maps and street views.