It started as radiant brushwork, which ended up being deleted and then resurrected in max through models. I tried converting brushes to .obj and then importing it to max but i didn't like the results, it splits the object down to faces and then each face is treated as a separate object and so on. Way too much work to put it all back together than it's worth.
I made one street in a development map a .ase model and imported that into 3dsmax -
Max version of the street
When I put the model back into my map I have some minor disagreements about shaders/materials - when I've worked this out it should be easy to add lots of curves and lumps in max.