During testing and research I found that the volvo handles the kerbs quite well, only the second chicane was wrong from my part. The kerbs there should follow the camber of the road so actually, on the inside, going down, and I had them raised. This gave an uncomfortable bump while in reality you basically have just almost 2 meters of extra road
In that same chicane are some heavy rumble strips*, and I intend to model everything as close as possible, so here a test of how low poly I can go. What I did here is have an edge every meter, which gets attached to the road and grass. Every meter will be subdivided 5 times, so that there is detail, but is all on the same plane, this initial 1 meter division should give enough roundess to start with I reckon. This one is screaming for nice texturing hehe, it'll be a while untill that stage though!
For people with motion rigs, these things will be a bit of a pain I'm afraid when I make them too high

(hard to control motion values for this modelled kerb)
Again I guess I'm changing my plans... While I'm at it, I'm just building the kerbs right straight away. I don't feel like going back an forth over and over again and rather do it right the first time around. First next public release will feature all kerbs for the normal track layout. Turtles and grasscrete will be omitted from that one probably.
*source:
http://designapplause.com/wp-content/xG58hlz9/2009/07/vectrix2.png
edit:
probably also taking a different approach to texturing kerbs, first 'm going to texture them without paint and get that to look good. After that it's only paint and rubber to be added, hopefully this will get me the feeling of the 'stone' in 'kerbstone'!
