The dissertation is devoted to a scientifically grounded approach to determining the optimal frequency of maintenance, which will ensure the optimal costs of maintaining vehicles in working condition with a given level of reliability, thereby increasing their efficiency. The cost of maintaining a vehicle in working condition can significantly exceed its cost. They depend on the operating conditions, which are individual for each unit of rolling stock, and are random in nature. However, rolling stock running costs do not always have to be minimal. If the additional costs allow to give a quality, the safety or reliability of the use of vehicles, that they become an investment. In this case, the required amount of operating costs must be optimal. The study was carried out on the basis of the Kiev motor transport enterprise Avtobudkompleks-K LLC, which has significant rolling stock and experience in its operation. With the help of analytical, statistical and expert analysis of the causes of failures, the main factors and their size of influence on the technical condition of vehicles have been determined. This made it possible to develop a methodology for correcting the frequency of maintenance, in order to prevent the occurrence of failures during operation and reduce their negative impact on the implementation of the transport process. The frequency of maintenance should not be constant, since at different times the car is operated differently and its technical condition does not change uniformly. To check the adequacy of the proposed methodology, a mathematical model was developed. It based on statistical data generates random transport processes and failure rates, taking into account which the maintenance frequency correction coefficient was determined using the example of KAMAZ and DAF vehicles in the dump truck and mixer specifications. Based on the one-criteria optimization, it was found that to ensure the prevention of most failures, the frequency of maintenance should be reduced for KAMAZ dump trucks 40.9%, DAF –34.4%, for KAMAZ mixers 41.9%, and DAF – 36.2% , which will prevent approximately 96.5% of failures. The rest of the failures are random, which complicates their timely detection and prevention. The economic effect of the introduction of the methodology, which makes sense for DAF, is expressed in the reduction in the cost of transportation by reducing the costs of maintenance and repairing, and the losses from downtime in them, which in general amounts to 14.39 thousand UAH/year for one dump truck, and for mixer – 17.71 thousand UAH/year. On the basis of theoretical and experimental studies, methods have been developed for determining the efficiency of using vehicles on the basis of technical and operational indicators, as well as recommendations for choosing the optimal design of a vehicle relative to operating conditions in order to increase its efficiency. A technique has been developed to search for the optimal design of a motor vehicle, based on the ratio of the cost of resources for its maintenance and its intended use to the general educational level of the possible amount of work performed by it under certain operating conditions.
