Railroaders call signals boards, and a yellow board tells the engineer to slow down and be prepared to stop at the next signal. With a heavy train that means getting the air set early, because a long freight needs a mile or more to stop. Following a slow train ahead produces a string of approach signals, which crews call running on yellows.
Yellow board at the east end, he's still in the plant ahead of us, so set some air and don't count on it clearing.
Engineers name signals by aspect, so a flashing yellow or a yellow over red tells a veteran exactly what to expect at the next signal.
Also heard as
- approach
- yellow
Related terms
Restricted speed
A speed slow enough to stop within half the distance you can see, used whenever the track ahead may be occupied.
CTC
Centralized traffic control: signals and switches controlled remotely by a dispatcher who routes every train.
Highball
A signal or radio call meaning proceed at full speed, and the verb for leaving or running fast.