Cell Size: An Important Factor for Modeling Bottleneck Traffic in Cellular Automata Model

In this paper the influence of cell size on the dynamics of traffic flow at an on-ramp is investigated by using cellular automata model. The two common methods, i.e., with or without ramp lane, for modeling the on-ramp system are both adopted. The phase diagram and the capacity of the on-ramp system are studied in detail. Capacity drop is a common phenomena at traffic bottlenecks, especially at on-ramp. The simulation results show that the capacity drop becomes more serious as the cell size decreases. Considering that in cellular automata model the cell size directly determines the acceleration rate which is not very large in real traffic, we believe that lower acceleration rate is one of the main causes for capacity drop. In order to modelling the realistic traffic behaviors at on-ramp, an appropriate cell size should be selected.