While in a VS3 drive on the paved road between Pustoshka and the constuction site NW of it. There are two of these invisible obstacles approximately halfway between the town and site, a few hundred yards apart. They seem to be more on one side of the road than the other. Traveling south on this road they are more to the left side, traveling north they are on the right. If you are driving slowly the VS3 will stop when it hits them. If you are going fast enough, you'll be pushed down through the terrain.