Interesting to see this hit roads.

This is how train speed in the NYC Subway (and likely other systems) has been done since the early 1900s.

Go too fast, and the train's brakes are activated.

The terminology is a bit off, but expected from community content. See the section "Timed Signals"

https://en.wikipedia.org/wiki/Signaling_of_the_New_York_City...