Based on the example of 6Dg type diesel locomotives, the paper presents a new maintenance strategy concerning periodical checks at the P1 maintenance level. Currently, such locomotives are sent off to service points every 102 hours of operation or every 14 days for a P1 level check. Studies demonstrate that the average distance to be covered by a locomotive to arrive at a service point is in excess of 60.0 km, and the quantity of fuel consumed is more than 88 litres. It is costly and time consuming to have locomotives out of service and considerable resources of the railway carrier are engaged which could be made use of in the transport process. The aim of the newly developed strategy of P1 checks is to eliminate the need for locomotives to exit their routes to reach rolling stock maintenance points. The control/diagnostic and maintenance activities specified in the Maintenance System Documentation will be performed by so-called mobile maintenance points. The development of the new strategy required: identification of the current condition of the maintenance system, development of the concept of a new strategy of P1 maintenance checks, conduct of studies and operational analyses for SM42 series locomotives, performance of a durability, reliability analysis, assessment of safety together with an analysis of the risks involved in the proposed changes. In order to review and assess the efficiency of the new strategy, an observed operation of selected locomotives was conducted together with a railway carrier. During the study, the maintenance activities and processes were monitored and the costs of P1 checks were recorded. The analysis of efficiency of the new strategy of performing P1 checks without the need for a locomotive to exit its route to reach a rolling stock maintenance point demonstrated that depending on the distance covered by the locomotive to reach a maintenance point, the unit costs of a P1 level check are lower by up to 67.1% compared with the currently applied method.

The article investigates the influence of preventive maintenance on the reliability and availability indexes of the railway means of transport, which also determine the economic aspects of their operation and maintenance. The research was done using the method based on fault tree analysis (FTA) and Monte Carlo simulation. The authors performed a cause and effect analysis of the occurrence of undesirable events during the operation of selected vehicles. They identified the weakest components of the rail vehicle that affect the downtime and mean availability most significantly. Specialized software including Weibull++, BlockSim, and MiniTab aided calculations were used to illustrate the application of the results of a modernization project involving a 6Dg diesel locomotive, carried out in cooperation with the biggest Polish rail carrier. The applicability of the proposed tools has been verified on the example of a selected sample of 75 diesel locomotives employing data on their use and maintenance acquired in the real operation process. The obtained results indicate that the proposed approach can be particularly useful in practice when assessing the applied rail vehicle maintenance strategy, and while developing new strategies and selecting the best one to implement.