Study On Real-time Level Of Service Based On GPS Equipped Floating Vehicles

As an important part of intelligent transportation system (ITS), advanced urban traffic guidance, of which premise of implementation is the acquaintance and control of real-time road traffic conditions, is carried out between traffic managers and road users. Traditional traffic parameters'detecting is relatively abstract so that it is not easy to build up the understandable relations between traffic-flow parameters and road users, such as traffic flow, density, occupancy and so on. Therefore, an understandable way is being needed to show real-time traffic conditions. Real-time level of service evaluation can play a significant role in this aspect.In traffic engineering, the present study results about level of service are mainly based on static road capacity evaluation, concerned with offline function quality analysis and applied for road planning and design. Comprehensive road LOS evaluation system in urban arteries based on advanced traffic management and information systems is not built yet in our country, hence the research described in this paper is concerned with real-time LOS evaluation system in urban arteries based on GPS equipped floating vehicles, which are both significantly theoretic and practical.This paper explained the meaning of LOS in urban arteries from the prospect of advanced urban traffic system management and information service. Based on the introduction of traditional LOS system, the traffic data collection technologies and the deep analysis of existing LOS algorithms, GPS equipped floating vehicles technologies are utilized for LOS real-time evaluation system in urban arteries, and so the architecture of the LOS real-time evaluation system is brought forward and analyzed in detail, including the referred technologies of system's actualization. Real-time LOS evaluating scheme is brought forward and labored, and it is pointed that the data process and LOS real-time evaluation algorithm are the key factors to implement urban arteries LOS system.In term of the LOS algorithm, based on data collecting and processing, fuzzy comprehensive evaluation model based on floating vehicles'status is proposed and designed. Several measures of effectiveness which are calculated from each floating vehicle are adopted, including the average section speed, variation coefficient of speed and low travel time ratio. Then the fuzzy comprehensive evaluation is processed on these measures of effectiveness and the real-time level of service class of the concrete road section is obtained.To analyze the performance of algorithms mentioned above objectively, the method to determine aggregation intervals and validate objectivity of LOS evaluation are put forward. The influence of the data sampling interval and parameters setting on the performance are studied, and two parameters are proposed, including percentage of one or more LOS jumps (POLJ) and percentage of two or more LOS jumps (PTLJ). Experiments about the model are processed with practical GPS equipped floating vehicles data in urban arteries.At last, the proposed model is compared with the direct classification method referred from current traffic engineering manual. The results show that the model subjected in this paper has higher POLJ and lower PTLJ than the direct classification method and is available to ensure the objectivity and practicality of LOS evaluation in urban arteries.