This book constitutes the refereed proceedings of the 4th International Conference on Reliability, Safety, and Security of Railway Systems, RSSRail 2022, held in Paris, France, in June 2022. The 16 full papers presented in this book were carefully reviewed and selected from numerous submissions. They cover a range of topics including railways system and infrastructure advance modelling; scheduling and track planning; safety process and validation; modelling; formal verification; and security.