A NONLINEAR TEMPORAL HEADWAY MODEL OF TRAFFIC DYNAMICS

In order to describe the dynamics of a group of road vehicles travelli ng in a single lane, car-following models attempt to mimic the interac tions between individual vehicles where the behaviour of each vehicle is dependent upon the motion of the vehicle immediately ahead. In this paper we investigate a modified car-following model which features a new nonlinear term which attempts to adjust the inter-vehicle spacing to a certain desired value. In contrast to our earlier work, a desired time separation between vehicles is used rather than simply being a c onstant desired distance. Zn addition, we extend our previous work to include a non-zero driver vehicle reaction time, thus producing a more realistic mathematical model of congested road traffic. Numerical sol ution of the resulting coupled system of nonlinear delay differential equations is used to analyse the stability of the equilibrium solution to a periodic perturbation. For certain parameter values the post-tra nsient response is a chaotic (nonperiodic) oscillations consisting of a broad spectrum of frequency components. Such chaotic motion leads to highly complex dynamical behaviour which is inherently unpredictable. The model is analysed over a range of parameter values and, in each c ase, the nature of the response is indicated. In the case of a chaotic solution, the degree of chaos is estimated.