Significant changes
Article 4
1. If there is no notified national rule for defining whether a change is significant or not in a Member State, the proposer shall consider the potential impact of the change in question on the safety of the railway system. If the proposed change has no impact on safety, the risk management process described in Article 5 need not be applied. 2. If the proposed change has an impact on safety, the proposer shall decide, by expert judgement, on the significance of the change based on the following criteria: (a) failure consequence: credible worst-case scenario in the event of failure of the system under assessment, taking into account the existence of safety barriers outside the system under assessment; (b) novelty used in implementing the change: this concerns both what is innovative in the railway sector, and what is new for the organisation implementing the change; (c) complexity of the change; (d) monitoring: the inability to monitor the implemented change throughout the system life-cycle and intervene appropriately; (e) reversibility: the inability to revert to the system before the change; (f) additionality: assessment of the significance of the change taking into account all recent safety-related changes to the system under assessment and which were not judged to be significant. 3. The proposer shall keep adequate documentation to justify its decision.