On the "Main Line" trains are usually referred to as going "up" or "down" by
the staff. However, it seems that, even "London Transport" refer to
Underground lines by their geographic direction; it's not just the public
signs that say "Northbound" etc. Is that correct? Did they ever use
up/down? I've seen it suggested that the reason for using "Southbound"
etc. is related to the American involvement in the building of some of the
tube lines; comments?

Help!