Let me know how you go acid!!! I have also tried this and its a pain in the ring! Wont you also have problems if you try and fit the road into the UV grid...as this will throw resoltion out the window for PS etc???? Have you tried some sort of shader...Ive been fooling with them for a couple of days...might be worth a shot...lets face it if you are driving down the road you wont be counting stones in the hotmix??
cheers bullet
bullet1968
"A Darkness at Sethanon", a book I aspire to model some of the charcters and scenes