Suggestions: Paved Roads in winter, that is maintained roads that have been plowed, sanded, or salted will look wet, ummm possibly darker? If the sun has had time to dry the roads after salting, they will look white -ish, ... hmmm, tough call. There are "metal gloss" textures for the paved roads where you can make them look wetter? not sure how it will look though.

The edges or shoulders of the roads will have snow on them, so they will look narrower? There are road edge textures, or borders that can be retextured for snow, as quite a few of them have green grass borders.

Dirt or "country" roads pre 1925 will usually not be plowed, but they will have had traffic of some kind on them. They would be white -ish with darker sand colored wheel tracks?

Then again, maybe you already thought of this.

Wunsch 1: Laubbäume im Winter sind ohne Laub richtig. Aber ein Wald aus lauter "toten Bäumen" sieht meiner Meinung nicht gut aus.
Wunsch 2: Schienen sind sehr schwer zu unterscheiden (Low-/Highspeed)
Ich hoffe dein Deutsch ist besser als mein Englisch
Google-Translate:
Desire 1: Trees in winter are correct without foliage. But a forest of loud "dead trees" does not look good in my opinion.
Option 2: Rails are very difficult to distinguish (low- / high-speed)
I hope your German is better than my English