A scientifically substantiated methodology of optimization of motion modes of machines and mechanisms (in particular, city-building cranes) based on minimization of integral functionals, which reflect undesirable properties of mechanical systems, and terminal (initial/final) conditions of motion of the mechanism of lifting cargoes by cranes have a physical meaning and are based on Newton's laws of mechanics, is proposed. The modes of motion of specific mechanical systems with a linear function of the position of elements are optimized on the example of mechanisms of load-lifting city-building cranes. It is shown that the influence of motion modes of drive mechanisms on dynamic loads in elastic elements of the mechanism of lifting mechanism of a city-building crane (ropes) is essential. The parameters of such modes of functioning/movement of such systems, at which exactly dynamic stresses of ropes at the stages of start-up of mechanisms of lifting mechanism of cranes are minimized, are determined. The results obtained in the work can further serve to clarify and improve the existing engineering methods of calculation of load lifting mechanisms of urban cranes in order to minimize the dynamic stresses of their rope systems at the start-up stage, as well as to prevent the occurrence of possible emergency situations. Such an approach can be realized both at the stages of design of the mentioned mechanisms and in the modes of proper operation.