In this paper the idea of treating the operational service workers as the elements of technique systems is suggested and the renewal theory is used to forecast the number of accidents caused by human factor. The analytical model is presented and limitations for its application are quoted. Furthermore, the simulation model is developed and the conditions for its use are given. The model observes each worker separately and establishes the exact time of arisen failures, the number of failures at some moment t, time tn, to the n th failure, inconsistency of failure number and total number of failures of the observed population. The model is tested on the sample of 348 engine drivers in PE “Serbian Railways” who have made at leas one accident, in order to research the parameters necessary for using the renewal theory and simulation.