This document is a first level identification of the systems and components that infrastructures managers and companies related with railway infrastructure consider the major origin of disturbance in service. The identification made was based on the strategic importance of the systems and components, number of systems / components at the network, number of failures per year and costs of maintenance. The systems / components presented cover almost all the technical areas in the railways, like switches, interlocking’s, tracks, embankments, bridges, tunnels, catenary and power substations systems, bottlenecks, vehicles, human factor and communications.