ABSTRACT
Considered either as a whole or separated (infrastructure - operation), railways constitute a complex system. Each component (track, traction, operation) has many sub-components (e.g. for track: rails, sleepers, etc.), the interaction of which is not easy to predict. However, a good synergy of all rail components is necessary in order to achieve the desirable result, i.e. safe, quick, comfortable and low cost transport of people and goods. For this reason, railways should always be examined as a system.
