Interpretation of traffic flow breakdown with density-flow model

To interpret the phenomena of traffic flow breakdown, common parameters of driving behaviors, such as headways and drivers' reaction time, etc., were analyzed. Models were derived to describe the relationships between flow and wave speed, speed and density, and density and flow. The curves for the relationships were obtained under different reaction time of different drivers during acceleration or deceleration. The simulated results indicate that the maximum wave speed decreases and the peak flow value increases with a decrease in reaction time of drivers, and that the change in reaction time is the essential cause of traffic flow breakdown.