THE GREEN WAVE MODEL OF 2-DIMENSIONAL TRAFFIC - TRANSITIONS IN THE FLOW PROPERTIES AND IN THE GEOMETRY OF THE TRAFFIC JAM

We carried out computer simulations to study the green wave model (GWM ), the parallel updating version of the two-dimensional traffic model of Biham et al. The better convergence properties of the GWM together with a multi-spin coding technique enabled us to extrapolate to the in finite system size which indicates a nonzero density transition from t he free flow to the congested state (jamming transition). In spite of the sudden change in the symmetry of the correlation function at the t ransition point, finite size scaling and temporal scaling seems to hol d, at least above the threshold density. There is a second transition point at a density deep in the congested phase where the geometry of t he cluster of jammed cars changes from linear to branched: Just at thi s transition point this cluster has fractal geometry with dimension 1. 58. The jamming transition is also described within the mean field app roach.