A numerical study of an asymmetric exclusion model for freeway traffic with two species of vehicles

Traffic on a one-lanefreeway with two species of vehicles is investigated u sing the asymmetric exclusion model with open boundaries. The vehicles are filed from their probability of jam, the fast vehicle can overtake the slow one. Using numerical simulations, densities and currents of vehicles are c alculated on one hand, as a function of the position in the road and in the other hand as a function of the rate of vehicles entry. The effects of the moving rate P-20 of the slow vehicles and the jumping rate Delta t on the (alpha, beta) phase diagram are examined. A passage from first to second or der transition occurs by decreasing the jumping rate and/or decreasing the moving rate of the slow vehicles.