Effects of back step and update rule on congestion of mobile objects

This paper studies the effects of back step movement and update rule on the traffic congestion properties of mobile objects, using computer simulation. The mobile objects are modeled as four-way-biased random walkers in two-dimensional square lattice. It is found that there is always a phase transition from free flow to jammed state at some critical density with and without back step under sequential and parallel update for large systems. Back step does not reduce congestion as one might expect. In fact, back step makes congestion worse in terms of critical density. The critical density with back step is smaller than the critical density without back step under sequential and parallel update for large systems. Back step under parallel update leads to completely jammed state, whereas back step under sequential update leads to partially jammed state. The critical density under parallel update is smaller than the critical density under sequential update with and without back step. Variable drift has no significant effects on the congestion properties.