Should work in the way you described first. You can essentially build floating roads (not the most realistic but it allow for way more creative freedom)

If i click on a road it always says, that the construction isnt working on this floor. I tried every street type.

Is the multi floor construction permit (or whatever its called) researched? You are trying with public roads?

so i was able to see that the mod is working. when i place the "up" road tunnel, it does place the modded on and i can build roads off that. but currently when i try to build the second floor. the two corners that we "place" needs to be placed on a first floor somewhere. i cant just drop off of the edge and it place the top floor. I can also remove the bottom floors and the top floors will stay.

so its working. however i feel like its not working 100%

for example:

build first floor foundation at 20x15 (LxW) where rectangle has the length running east/west

go up a floor and starting on the bottom right of the first floor foundation. drag off, up and to the left, 15x40, running north south.

and it says i cant build on this floor.

Idk if i can post pictures.

sorry for the late reply. i was not home all weekend

Originally posted by Humoresque:

Is the multi floor construction permit (or whatever its called) researched? You are trying with public roads?

does the mod have its own research?

The mod doesn't have its own research, but you do need the in game multi floor permit project to build anything on any floor besides 0...
Ill look into this issue, somehow havent seen it before. Maybe because im playing with no construction... still seems odd. But thank you for your help