Abstract
The article deals with the optimisation of dependability requirements on a vehicle from the producer and user point of view. The authors are presenting mathematical models of user and producer costs as are production cost, warranty cost, maintainability cost, etc. All the costs are expressed as a function of the dependability level. The presented models make it possible to review dependabilitys influence on costs. The general persuasions of optimisation of dependability requirements are indicated. The problem of the growth of dependability under minimal costs is solved too.