if you mean like race tracks, and for 3ds/b3d export, get 3ds max, dummy!
Right, because anyone who doesn't either :
(a) have £3,000 lying around behind the sofa, or
(b) want to steal software
is clearly a dummy. < At this point, I really wish there was a rolling eyes emoticon for this board. >
On Topic, there used to be a really good track editor. We're going back a few years now, and I'm not sure if it was written in B3D or not, but I remember it had been used for a few different games. It was pretty cool, used splines and everything. Hopefully me babbling inanely about what little I recall of it will remind someone who might still have a bookmark.