Looks like it’s mostly a UK, Australia, and New Zealand thing.

It’s in mph. 240 kph. Article says: “this article lists all the systems and lines that support speeds over 200 km/h (120 mph) regardless of their statuses of upgraded or newly built.”

A while ago I read a book where a town got nuked. Only it was just a rumor spread on Facebook. Town is fine. But tons of people believed it. Set up road blocks and stuff. For years.

edit: I thought, “there is no way people would do that.” Oh well.