Using the example of one section of a railway line, the effect of various factors on breaks in train service has been analysed. The types, number and duration of breakdowns, as well as their influence on both passenger and goods trains service have been specified. The traffic capacity of a railway line is related to the possibility of meeting the timetable, which is therefore affected by all breaks. It is very important to know the type of breakdowns, their number and influence on a railway line capacity as well as their causes