Abstract:According to the problem of low performance price ratio of license plate recognition systems which are just for traffic monitoring,traffic flow measurement etc,and the lack of researches on traffic congestion identification methods based on license plate recognition data at present,methods for collecting travel speed of individual vehicle and link average travel speed are designed,and based on these,a method of traffic congestion identification is studied,which is also verified by using measured license plate recognition data on a arterial road of a city in China.The results show that traffic data with high quality can be obtained using the travel speed collection methods,and the duration and types of traffic congestion can be obtained using the traffic congestion identification method,which will provide real-time and reliable decision basis for traffic management departments.