This phrase is reputed to have been heard on the railway radio over a scanner. I think I know what it means!
Before the days of radio, crews had to
use hand signals to
give movement instructions to the locomotive. When
I first came to
The Thurso and Nation Valley Railway had an additional complication. Their road locomotives were all GE 70 tonners which were setup to run long hood forward. The TNVR wanted to improve visibility for locomotive crews but would not go to the expense of changing over the control stands to make it easy for the engineer. The standard procedure was for all TNVR trains to be run with the lead locomotive running backwards. However, the crews made a rigid distinction about which was the front and which was the back of the locomotive. Thus if a train was ready to leave you would hear the instruction “Back up (reculez)” which was the instruction to leave (i.e go ahead).
This took a bit of getting used to and the TNVR was one of the few railways where “Go ahead and back up” really did mean something.