The railway signalling is a system used to control the traffic on the Railway and thereby prevent accidents. The railway signalling in Sweden is a safe system and not a single train passenger has died as a result of an accident since year 2010. However, as railway signalling has been developed nationally and has not always been compatible with each other, a problem has arisen when trains travel between countries. To enable a more compatible signalling system a standardized and digitized system called European Railway Traffic Management System (ERTMS) is now implemented in Europe. Trafikverket (TRV) is responsible for the implementation of ERTMS in Sweden and a ERTMS-programme is established. ERTMS is expected to med implemented in Sweden by 2035. To maintain a safe railway system in Sweden, the implementation of ERTMS need to be at least as safe as the current system. This can be ensured by following different requirements stated in standards regarding safety. The European standard EN 50129, "Railway applications - Communication, signalling and processing systems - Safety related electronic systems for signalling", is one of these standards. EN 50129 is updated from an old version to a new version. The purpose of this master thesis is to identify and analyse the effect of the update of the European standard EN 50129 on the implementation process of ERTMS. In addition, this study aims to suggest which actions need to be done at ERTMS-programme to implement the new version of the standard. To investigate this a qualitative method is used which involves a literature study, an analysis of the differences in the standard and semi-structured interviews with persons working at TRV. Theory about safety, safety management and the concept of Safety-I and Safety-II is used in order to analyse and discuss the safety management at ERTMS-programme regarding the update of EN 50129. The results in this study show that the new version contains some new requirements that need to be implemented in the safety work within the ERTMS-programme, for example IT-security and human factors. Furthermore, the new version also contains additional explanations of subjects which can be helpful in the daily safety work. However, the study also shows that the new version involve already known requirements to a great extent. Therefore, regarding these part, the effect of the update is small. The suggested necessary actions are partly about implement the identified new requirements but also about implementing a more proactive safety approach and share the knowledge about the new version.