[zipzapp]

I don't understand what you are meaning with to plot a second road (or rail). You can create a road or rail only by setting a pixel in the map_t. One pixel is 200 meter wide in the map. The only other possibility to lay rails is to use a rail from the rail objects in the fmb. You can build a railway where you want with that, but that would be a dummy railway.

It's also not possible simply to change the road texture to a rail texture in map_t. It's no problem to write a program for this and a