Method for estimating city road network traffic flow state

The city road net traffic flow state estimating method is based on vehicular GPS data combined with SCATS provided traffic signal state information. The present invention establishes city road net traffic flow state model by adopting unit oriented road sections as targets and through least-square method fitting in the three-dimensional space of distance, time and speed. Through the conversion from curved surface in the three-dimensional space to the curve in the two-dimensional space, the average speeds in various oriented road sections of the city road net in fixed time are obtained, and the current traffic flow jamming state is analyzed and estimated with speed as index. The traffic flow state estimation is completed through establishing the traffic flow state model for each of the unit oriented road sections between two signal lamps and connecting the curve surface models of adjacent equidirectional road sections.