Coexistência de fases induzida por um mecanismo de direção defensiva em um modelo de autômato celular para fluxo de tráfego

Abstract

Traffic flow modeling is an elusive example for the emergence of complexity in dynamical systems of interacting objects. In this work, we introduce an extension of the Nagel-Schreckenberg (NaSch) model of vehicle traffic flow that takes into account a defensive driver’s reaction. Such mechanism acts as an additional nearest-neighbor coupling that can trigger avalanches. The defensive reaction dynamical rule consists in reducing the drivers velocity in response to deceleration of the vehicle immediately in front of it whenever the distance is smaller than a security minimum. This new mechanism, when associated to the random deceleration rule due to fluctuations, considerably reduces the mean velocity adjusting the distance between the vehicles. It also produces the emergence of bottlenecks along the road on which the velocity is much lower than the road mean velocity. Besides the two standard phases of the NaSch model corresponding to the free flow and jammed flow, the present model also exhibits an intermediate phase on which these two phases coexists, as it indeed occurs in real traffics. For small values of the density, the jammed phase displays some characteristics of synchronized flow. These finding as consistent with empirical results as well as with the general three-phases traffic theory.