Blocking the road might be a challenge since that would require them to know it's actually there, which I think isn't the case. When you're talking about third-party scenery, it's a good chance that the road is just a texture that's built into the scenery, so there's really no good way to check it. The only way I could theoretically see it happen is if it checked for vehicle paths, but that would require the scenery developers to actually put those in, which most don't. This is also why you may see vehicles driving around on taxiways and even runways rather than the road.
