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

[Randy]

Martin Koppenhoefer wrote:

I concede.

In fact my OLD Encyclopadia Britannica states that a tunnel is excavated 
underground and a "cut and cover" is not truly a tunnel.

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".

-- 
Randy