The 4th International Conference on Reliability, Safety and Security of Railway Systems will be postponed to the 1st and 2nd of June 2022 due to the pandemic. The papers submission deadlines for the conference Call for Papers has also been postponed. So, in 2021 the conference will be replaced by a special issue of the journal Formal Aspects of Computing (submission deadline extended: 12th July 2021). Next year, the physical event will be held in the International Union of Railways Congress Center in Paris.
