Willis
I will try and see if this makes sense. On some railroads, infact all that are in my area, don't use signals for movement. So in order to control the trains on a single or even double track they will use the radio to issue what is similar to a Train Order. So If I am at milepost 10, and I need to get to milepost 30, I need to be sure I can get there without running into another train, or be sure there isn't another train. So what normally happens, is the dispatcher will call a train, usually by the lead engine numbers and road mark ie:
Dispatcher to UP 5608
The engineer or conductor will respond and the dispatcher will start reading off from his computer or a large sheet of paper (I would imagine)
So he will say:
Track Warrant #100 to the UP5608 at 13:00 hours on 10-3-2005,
X Box 2, proceed from milepost 10 to milepost 20 on Peoria Main track.
This warrant has 1 box marked 2 dispatcher DET
The drew would read it back exactly as it was given, then the dispatcher will okay the warrant. Now the crew can power up and run to milepost 20 assured that no other train in in their path.
Once the train has reached milepost 20, they will contact the dispatcher and clear the warrant so the dispatcher knows that milepost 10 to 20 is now clear.
Hope that makes sense, it's a condensed version. Here is a link to a more indepth definition of a track warrant.
http://www.lundsten.dk/us_signaling/twc/
