Analysis and Control of Recurrent Traffic Congestion on Urban Expressway

In order to control or alleviate traffic congestion effectively, work must be done to analyze the evolvement, causes, and key parameters of traffic congestion. Firstly, the paper classifies six typical traffic states, and defines three types of recurrent congestion according to their evolvement. For speed "fall" usually occurs in on-ramp merging area, we put forward "state transition" and use it to explain the evolvement of recurrent congestion. Then, an approach of identifying traffic control area and congestion source using "spatial-temporal speed figure" is introduced. Lastly, in order to predict congestion, we present congestion threshold and its identification methods, and use an example to test the impact of two factors. The research can provide reference for selecting suitable traffic control strategy and identifying the optimal occasion to implement it.