[Tagging] Are tunnels only below ground? (Was Highwaypropertyproposal "covered-yes")

[Anthony]

On Tue, Nov 3, 2009 at 1:06 PM, Randy <rwtnospam-newsgp at yahoo.com> wrote:
> So the question now is how to tag an above ground "tunnel-like" structure
> to properly indicate it's characteristics, that is "completely enclosed on
> all sides, save for the openings at each end".

For what purpose?

Covered=yes, barrier=highway?  Preferably the barriers would be mapped
separately, but I suppose they could be combined for the sake of
easier editing.