That's because you've used terrain that uses global UV mapping (ie you cannot manipulate single face texture positions, the whole project uses the same orientation..) Instead of terrain, you should use track for runoffs. I suggest you download this:
http://cream.galleria.fi/BTB/XPacks/CK-Tools.zip It has several track crossections that has multiple materials. Study those to get the idea..
I tried to find a good picture but if you look at this post:
http://www.racedepartment.com/forum/threads/cicada-gp.29603/page-4#post-1074725 No need to watch the video, the preview screen shows an example. There is 6 materials in the track: green rumblestrip, blue/metal drain, left side of road, right side, drain and rumble again. Terrain starts AFTER the rumblestrips. Basically the best choice is to use track for all driveable surfaces and terrain for only terrain (and for ex graveltraps...) You can use grass/gravel as a part of track too, for ex in places where there's no rumblestrips but the track goes straight from tarmac to grass.
I know i didn't explain this properly but i hope you get the picture.. Load that XPack and test it with new project before incorporating it to your main project. There are more XPacks here:
http://cream.galleria.fi/BTB/XPacks If you use BTB Evo, then you need to replace the default XPack with the one found in the Community Collection, it has CK-Tools included plus it has functioning startlights (BTB EVO Default XPack has a startlight animation bug...)
Keep the questions coming and try to use search, there is impressive backlog of answers to all sorts of questions.. I didn't know in the first 6 months that you can use multiple materials in the track since it's not mentioned anywhere.. Track uses the same method as walls do and you can even design track crossections with the wall tool, copy shape&materials and paste them to the track. Only thing that needs to be identical between the two is the number of points....
Remember to play with the scale in the road material menu. There should be a "car for scale" XPack that has very simple racingcar in it, use that to find correct texture sizes (bookmark that location, it's the default community XPack collection until a more proper solution is provided.. If we ask very politely, maybe we can get the RD archives back....). It's very easy to get out of scale, just like you saw on that Cicada preview screen (the drain is just awful in that version, the metal mesh is just out of scale, way too large.) It's good to use those default materials in the initial designing phase and when the track geometry is in place start editing textures to fit the new dimensions...
