An improved method for estimating urban traffic state via probe vehicle tracking

In order to estimate the state of urban traffic flow, a Probe-Vehicle-Tracking based method is proposed in this paper. The method collects traffic flow data with Global Positioning System (GPS)-equipped taxies, which are taken as the probe vehicles. Then, the A* heuristic search algorithm is employed to judge the optimal vehicle tracking path. In addition, the average velocities of road links are calculated by considering the velocities of vehicle tracks as well as their corresponding credibility factors. Finally, an experiment with massive real-world traffic data in the surface road network of Shanghai was carried out, and the ground truth of the average velocity was obtained by repeating the videos shot on the 24 links in Shanghai downtown. The experiment results verify that the method has high accuracy and can be applied in engineering practice.