An important issue in the validation of mechanical parts for vehicles is reliability assessment for high mileages, by means of tests. Since the tests should be as short as possible, and for parts subjected to degradation mechanism, such as wear or crack propagation, it would be appropriate using degradation measurements (such as mass loss or crack length) in order to estimate reliability. In this study, we present some statistical approaches responding to this concern and propose a method to compare theses models. Different types of data can be available; in this paper, we only consider the case in which one measure is available for each part. Only linear degradation is studied.