This paper deals with road traffic simulation performed on a cluster of computers with multi-core processors. Two versions of the simulation are compared -- the distributed version and the parallel/distributed version. The distributed version utilizes a number of single threaded simulation processes. The number of processes corresponds to the total number of processor cores of the cluster. The parallel/distributed version utilizes a lower number of multithreaded processes. The number of processes corresponds to the number of computers of the cluster and the number of threads per process corresponds to the number of processor cores of each computer of the cluster. The parallel/distributed version minimizes the inter-process communication using the shared address space of particular threads in one simulation process. Hence, it is significantly faster than its pure distributed counterpart.