In many countries, pedestrian crossings have a button you press to signal your desire to cross. After a little while this makes the traffic lights go red for the cars and lights up a green man allowing you to cross.
Often you press the button whilst some cars go past, then realize there is no more traffic, so you cross the road. The lights don’t know you have already crossed so a bit later the traffic lights go red and the cars stop and wait whilst no-one crosses. Wouldn’t it be much better if there was a button you could press just before you crossed saying that you don’t need the lights to change any more ?