Tom Remberg is chief information security officer for Bane NOR, a state-owned company responsible for the Norwegian national railway infrastructure. He discusses the need for “different layers of protection” and “high-availability elements” for mission-critical systems undergoing a digitization program. He says that in order to avoid adverse business impacts in case of an outage, everything must be duplicated and it must be possible to “take one part of the infrastructure down, maintain and upgrade it, while the other one is running””]
Source: https://www.careersinfosecurity.com/digitizing-securing-norways-railway-network-a-17857