Modeling the probability of vehicle failures by operating time within a maintenance cycle

Motor transport enterprises often conduct maintenance of vehicles under warranty service using their own facilities. Due to the influence of various factors, the actual operating time between maintenance operations often deviates significantly from the normative ones. Existing methods do not allow accurately determining the change in failure probability for a vehicle group, because the actual operating time at the completion of the maintenance cycle is a stochastic value. This paper proposes a method for evaluating vehicle maintenance quality, based on the ratio of failure probability increments before and after maintenance, taking into account the specific operational characteristics of the vehicles. The research employs an axiomatic method: the failure rate decreases after maintenance and increases with accumulated operating time. The research hypothesis posits that maintenance quality can be assessed by the ratio of failure probability densities in sections before and after maintenance (first section: operating time 0 to 7.5 thousand km; second section: operating time 7.5 to 15.0 thousand km). Data on vehicle failures during actual maintenance intervals were collected and processed for two structural divisions of a city-forming enterprise in Surgut. The developed mathematical models are statistically significant with a probability of 0.99. The resulting values of the developed quality indicator – 1.947 for the first enterprise and 1.731 for the second enterprise – indicate that the system for ensuring the operational reliability of the investigated enterprises is effectively organized. Further work is planned to evaluate the maintenance quality across different car brands to obtain a broader spectrum of values and facilitate their subsequent interpretation.