In message , MarkVarley -
MVP writes

I have no idea what they're called, the LED signs in some bus stops
that tell you how long the busses are supposed to be, my question is,
how do they work? how do they update?

The current system, called Countdown, is fairly primitive. When a bus
passes a fixed point (with a large bar-code) earlier along the route,
the system simply adds the standard time it takes to get from that fixed
point to the bus stop at which you are waiting. If the bus subsequently
gets delayed, it knows nothing about it. Equally, if the bus is diverted
or is too far from the curbside to trigger the reader, or if it is
overtaking another bus (or any large vehicle) as it passes the bar-code,
the system know nothing about it.

The Countdown system is currently being replaced by a rather better,
GPS-based system.
--
Paul Terry