In this paper, we present and discuss the advantages of cloud-based safety monitoring for railway control systems, using digital twin technology. It is explained why additional safety supervision techniques will become necessary in the near future, to counter increasingly threatening security attacks and to cope with the complexity of ETCS Level 3 systems or even fully automated driverless systems according to GoA 4 and beyond. The presentation is informal but structured: we show how existing technologies and theoretical results can be used today to prepare for the safety-related challenges of tomorrow’s railway control systems.