The solution is to use 3D models instead of walls where possible.
For roads there is a nice Furniture Library: https://sweethome3d.com/support/forum/v ... 1079#51676

Another trick is to use Rooms for roads/driveways. Enclose the area in walls and double click inside to create a room. Then remove the walls. A room is a much simpler object than a wall and you can still take advantage of curves like with walls. It's also easy to modify it by editing the room points. A room also has the advantage (for a road) that is has no height.

You can create road pieces with walls or rooms and export these. Then import an re-use them like with the models from the library.