Or you could try and make a terrain in your model program. Nake it FPSC reloaded ready and import it as an entity. Set its height to what to what in the map editor and then sculpt the terrain in reloaded to copy your entity terrain as close as you can.
Back in your model program you can then draw a spline to the contour of your terrain and then loft the road to that.
Make that Reloaded ready and import into your map and it should be very close match. I did that in the comp entry I did 'Escape From Treasure Island, California'
Worked out pretty good over all. Still a bit of work to complete.
Hope this helps out till a better solution can be had.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 4gb RAM, Nvidia gtx660, Windows 7 Pro 64bit
