A hierarchical model of a large-scale system including a control Centre and a transport monopoly is considered. The mechanism of control of the transport monopoly is defined. The decisions of the game of monopoly with the control Centre are considered. The task of the optimal synthesis of the control mechanism is set. Sufficient conditions for the optimality of this mechanism are found when driving vehicles along a ring road with a prohibited overtaking (for example, by rail or a single-lane highway). The cases of the optimal balance of supply and demand, as well as scarce demand are considered. For the case of excessive demand, sufficient conditions for the optimality of the number of vehicles and the carrying capacity have been determined. Some conditions for the optimality of control mechanisms for road and rail transport have been found.