[Tagging] Railway routes in different directions.

[Dave F.]

  Hi

I've a railway routes that's drawn as a single line with a relation 
added; except where the tracks become wider apart to go each side of a 
platform where they are two lines.

Does routing software need the relation to differentiate between the 
directions? Up/Down, Forward/Backward?

And how would you decide which direction is which?

Cheers
Dave F.