A Model for Speed of Shock Waves in Bottleneck Waves

The occurrence of accidents or other incidents in the traffic flow is one of the factors that disturb traffic flow. As an accident happens, shock or turbulence is transmitted as a wave to the current flow of traffic, causing a change in speed, density, and ultimately resulting in delay. The purpose of this study is to investigate the traffic flow behavior and its changes through a shock or disturbance. In this study, three crashes were completely filmed on the Sadr highway at Shariati intersection in Tehran. All parameters of volume, queue length, queue growth, speed, delay, and density were calculated for all three locations. The results showed that the ratio of changes in traffic flow to changes in density as an independent parameter is effective in the wave-speed model. Four models were presented in this study. The assessment of the significant level values showed that except for the inverse model, the rest of the models have desirable values. From the remaining three models, the linear model thanks to its simplicity and higher F coefficient was selected as the final wave-speed model. According to the results, if the profile of a road is known and then an accident occurs, it can be predicted which locations the accident will affect. It is also possible to redirect the current traffic flow from the incident site to other routes and reduce the traffic load.