Am 14.04.2018 um 15:23 schrieb Torben Brand:
> We use mainDir for three things:
> 1. to indicate on a macroscopic level if the line is single
> (mainDir="none") or double track (mainDir="up" or "down")

Actually, reasoning is only possible in one direction: if there is a
single track line, it cannot have a main driving direction and the usage
of @mainDir="none" is recommended (see [1]. It is not possible to
conclude from the main driving direction whether a line is single track
or double track. The remaining question in particular: how to
distinguish between single track line and double track line without
preferred main direction?

> 3. to indicate the position of the track in a mesocopic
> level (mainDir="up" track on the right side in increasing
> mileage)

Sorry, but I do not understand the meaning of this usage scenario. Could
you please provide an example for a track with mainDir="up" and
mainDir="down" following your proposal? From my current understanding,
this approach does not work since the rule "driving on right side" is
not unique among European railway lines and even can differ along a
single railway line. However, maybe your examples may convince me ;-)