CLUSTERING OF CARS IN CELLULAR-AUTOMATON MODEL OF FREEWAY TRAFFIC

A cellular automaton (CA) model is presented to simulate the clustering (or aggregation) process of cars in traffic flow on a highway. The CA model is an extended version of the one-dimensional asymmetric simple-exclusion model taking into account the variation of car velocity which depends on the distance between a car and the car ahead. Using computer simulation, it is found that clustering (or aggregation) of cars occurs in our model. The mean distance [l] between cars scales as [l] almost-equal-to t0.37 +/- 0.02 where t is time. Similarly, the mean cluster size [s] of cars scales as [s] almost-equal-to t0.37 +/- 0.02. It is shown that the cumulative cluster-size distribution N(s) is not a power-law type but an exponential function N(s) almost-equal-to [s]-1 e-1.72s/[s].