The railway network composed by different systems, such assignalling, power supply, rolling stock and others. The signalling system is used for control, supervision and protection of railway traffic. Its reliability, maintainability and related maintenance support affect the availability of the railway network. Often,signalling system itself is considered as a system-of-systems spread over a wide geographical area and consists of a large number of items with different lifecycle. However, managing a complex technical system with large number of items in different lifecycle phases to achieve required availability is challenging. One major challenge is to define and describe the structure and relation between the system’s inherent items at any specific period of time, i.e. the configuration of the system. The system configuration is important during the design and manufacturing of systems, but it is also essential during the utilisation and retirement of a system. Furthermore, system configuration can be considered as an essential data container to which other data sources can be related, e.g. design data, reliability data, maintainability data, operation data, and maintenance data. Aproper management of configuration data is highly important during a system’s whole lifecycle, e.g. the railway signalling system. Hence, the purpose of this paper is investigate how the process of configuration management related to railway signalling system can be improved through utilisation of Capability Maturity Model Integrated (CMMI).