A statistical model of traffic flows designed for modeling the motion of vehicles on long highways is proposed. The model simulates the motion of groups of vehicles on the road using the fundamental flow–density diagram on a selected segment of the road with the purpose of calculating the speed of the group; it is assumed that the group size linearly depends on its speed. The proposed approach combines the advantages of macroscopic and microscopic simulation. That is, it allows one to simulate the motion of vehicles in megalopolises to a high accuracy and with low requirements for computational resources. The principles of simulation are described, algorithms for recalculating the model states are presented, and computational experiments confirming the validity and workability of the simulation results for various configurations of the road network are discussed. In the experiments, the fundamental flow diagram is constructed on the basis of sensors of the traffic control center.