Traffic Congestion Identification Method for Urban Expressway

In order to make up inadequate research on traffic congestion identification by single detector ,this study focuses on using actual single detector data to recognize congestion .Based on analyzing the field traffic data ,critical occu-pancy can divide the state of traffic flow into congested and uncongested flow .Speed to occupancy ratio and speed differ-ence can design a multiple indicator identification method to determine the time of congestion occurrence and end time .Fi-nally ,after three indicators threshold are calibrated ,this identification method is applied to Beijing urban expressway . The result shows that this method can identify congestion effectively in starting time ,duration ,and finishing time .