A.I on maps without terrain

I have recently downloaded the Nordschleife map and played in it a little bit, after a while I tried to make the A.I do a lap but it didn't move at all, I tried making a road for the A.I on the world editor but it says I need to create a terrain, how do I make the A.I work in this map?

 

Thanks for the reply! and sorry for only seeing it now, I tried to make the waypoints on the mesh road editor manually and when I finished it and clicked to put the A.I road on the road editor it still required me to have a terrain. So I tried making a terrain beneath the map and placed the waypoints on it, but when i put the A.I to follow them, the waypoints weren't aligned with the track. Is there any way to make the terrain have the shape of the 3D model so I could put it right beneath it?

 

Thanks for the help but this is just far too difficult for me to do, I can't preview the path the A.I will follow so I won't know if I've put enough waypoints for it to do the curve or not, and it's a pretty curvy circuit with lots of irregular areas, I don't have enough time (and patience) to do it, but I do thank you for your help and tips.