slow bus to nowhere

Today driving home from work I almost got stuck behind a bus. Fucking buses.
Why can't there be a light on the back of the bus that lights up whenever someone pulls the cord inside? Simple, driver-friendly stuff that will never happen. Like fuel-efficiency. (yes, I realize that this is about a train, albeit with a cool name, and I really wanted the story on the buses in Denmark that use the same principle. But if I've been too lazy to post for weeks, I am certainly too lazy to be all properly linky right off the bat. This is my search, if you are so inclined.)