The same goes for vehicles, although, you can play around with the Route-Ribbon™ to try to figure out where you can actually drive, even if it might take a couple of turns to get there.
Suggestion/Request
Put a button on all units* that overlays all hexes into which an helicopter can land. Unless I'm mistaken, if an helicopter can land in an hex, a vehicle can also drive there, if there is a contiguous set of connected hexes to the target location. This would display like when you click on the Build FOB button on the Buffalo, which shows you an overlay of viable target hexes.
This would be very, very helpful

*Especially Infantry and SF need this to know where LZ's are, so they can move to next to one. It would also make the accessibility of valleys apparent for vehicles.