A Car Following Model for Motorway Traffic

This paper presents a new car-following model which aims to capture some of the key motorway flow characteristics, namely traffic breakdown, hysteresis, shockwave propagation as well as close-following behaviour. The model proposes three different driving states: non-alert, alert and close-following. Under the different driving states, drivers apply different reaction time and acceleration. This paper presents the formulation and algorithmic implementation of the model. Theoretical analysis of the macroscopic flow-density relationships of the model is discussed. Simulation experiments are conducted and the results are examined at both the macroscopic level with regard to speed breakdown and traffic hysteresis, and the microscopic level with regard to gap distribution and shockwave propagation. The results show that the model is able to realistically capture the speed drop, traffic hysteresis and shockwave propagation as well as close-following behaviour. Further sensitivity studies of the key model parameters suggest that the drivers’ reaction times have a significant effect on the modelled capacity and occupancy, whilst the effect of the speed threshold which distinguishes a congested from a non-congested traffic flow is less significant. Wang, Liu and Montgomery 3