Effective fleet management is related to the care for their rational use and proper diagnostics. Early detection of potential irregularities enables to prevent failures and carry out transport processes in an undisturbed way. One of the most important components, from the safety point of view, is the braking system. Laboratory tests can be used to determine the durability characteristics of individual components. Individual indications referring to operating conditions would be most desirable. The article, based on a two-year period of testing of a group of Renault vehicles fitted with disc brakes, presents measurement of wearing and tearing the system components (brake discs and brake friction insert) in a function of selected factors, depending on the time and environment in which the transport was carried out. Nonparametric statistical tests were used to analyze the results. Mann-Whitney and Kruskal-Wallis tests were used to verify the hypothesis on the insignificance of differences. Their results were compared with the results of ANOVA variance analysis. The significance of factors influencing the degree of brakes wear was checked. Possible directions of using the results of brake wear measurement for rationalization of transport processes were also indicated. Presented method may also be applied to the evaluation of other components (assemblies, subassemblies, systems) of motor vehicles.