Abstract
It is well known that motor vehicle's failure isn't predictable event. However, in organized bus transportation systems, where intensity of using and exploitation conditions are dictated by passanger needs for transportations (number of passangers, destinations, freqence of transprt etc.), it can be seen functional dependence between failures during working time. It is very important not only for availability of transportation systems, but for maintaince sistem too, that probability density of failures during working ours is mathematicly determinated and statisticly proved. It is also necessary to have good information sistem which is able to colect informations about real times at the moment of failures, and how much time is needfull for service. In this paper it is shown how to optimise maintenance system based on the model which use modelnig time at the moment of failure, modeling time necessary for service (including 'waiting time') and simulation which is used to simulate one working day. Real statistic results had been used for modeling times.