The number of operational rail corridors equipped with ERTMS is increasing throughout Europe. The implementation of this critical safety system is planned to take several decades. However, ERTMS is a complex system that evolves continuously increasing the risk of using outdated parts and components. Therefore, adaptability is required for an efficient process. Adaptability is the ability of a system to meet technological or functional changes without requiring structural modifications or replacements. This paper identifies factors that influence adaptability and researches critical issues for future adaptability of ERTMS. With these factors and issues, solutions are proposed that are validated in a use case and integrated in a strategy that strengthens adaptability of ERTMS for future operational needs. The main takeaways of this strategy is the need for technical modularity and a balanced stakeholder involvement in the implementation process.