I would make it like this - everything belongs to the track, which has three-part crossection: middle part for the road and roadsides. The textures were taken from Default Xpack (I just skip bump & specular maps). The road itself and outside grass are just original textures. The most important thing was to make:
- the roadside (just the grass with some tarmac and a thin "stripe" of sand) - now it looks more like worn road edge
- the "sand trap"
- also, the start of sandtrap (which is actually also the end - the material is positioned then "upside down").
So, there are altogether five textures in project's XPack.
It needs just little time to add new sections with Material Change and add proper materials (and flip them horizontal and/or vertical to fit them to various places). Note that the sandtraps don't have to start at the same places, since we have left and right side... But I would not suggest to add new material sections in the middle of textures. The default material change was 12 meters, and panel lenght was 5 meters - that made approx. 3 squares (road's polygons) in a line to place new sections. You can still move the sections (hold M + drag the red section's line) a little.
I've added some little shape to the sandtraps and randomness to make them be more "dangerous"
You can still play with the width of the roadsides/add more shapes - I did not want to spend time on it.
After you are satisfied with your building (after you have set global track's widths/angles etc), you can add terrain (conventional way) and fill it with grass texture. There's is actually some terrain in the attached project - I did not pay too much attention for the number of polygons, so maybe there too many of them for rFactor.
Here is the BTB project if you want to check how it is done:
I hope it will look good in rFactor too!
http://www.sendspace.com/file/plq8mx
NOTE: You need to add Default XPack there to avoid errors (but the project works in "my" BTB even without it)
... and .psd file if you like the sandtrap texture (Photoshop PS2, I hope you can open it with earlier version):
http://www.sendspace.com/file/pyq5zn
The sand texture was also from Default XPack, painted a little
This way you can use more textures to make the track look even more interesting...
And this was how I've build 100% of the roads and roadsides in my GB Sprint rally stage
(the crossections were just more complex).
R Soul's method is still great, I would use it for texture transtions placed more away from the main track/road
With "blending" like that you can use your own texture mixing AND avoid blending materials in BTB, which can be not accepted if you would like to convert the track to original RBR format.
And finally -
IMPORTANT (rFactor) - I'm not sure if I've set proper surfaces for the materials - please check them in XPack first.