Some transition must be on both sides, but perhaps you would want a different transition on each side.
There's not much space left for way point data, due to alignment rules on the GPU doubling the parameters would consume twice as much memory for the roads. But there are two things that can be done now.
There are internal flags to create only the left or the right side of the road. Roads with different parameters on the sides could be created from a single road by cloning. However, I would like to hide this process from the user, automatically doing this once the road parameters are split in the editor. But it complicates other things, selection of roads etc ...
Another thing that can be done (independently from the first) would be to automatically adjust the transitional areas according to the lateral slope. Note, this is already being done for curves, transitional area of the inner side is shortened.
When you are on a slope, you cut into the hill, so the side facing downwards would have a short transitional area.
