[Tagging] Are tunnels only below ground? (Was

[Peter Childs]

2009/11/4 Andy Robinson (blackadder-lists) <ajrlists at googlemail.com>

> oh and I forgot to give a word of warning in the other direction. Some
> structures that you might think are bridges are actually tunnels because of
> the way they were constructed, but I'll leave that to another day ;-)
>
> Cheers
>
> Andy
>
> >-----Original Message-----
> >From: tagging-bounces at openstreetmap.org [mailto:tagging-
> >bounces at openstreetmap.org] On Behalf Of Richard Bullock
> >Sent: 04 November 2009 9:39 AM
> >To: tagging at openstreetmap.org
> >Subject: Re: [Tagging] Are tunnels only below ground? (Was
> >
> >> 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".
> >>
> >We don't *have* to stick to dictionary definitions here when tagging, as
> >long as the meaning is clear;
> >
> >If it walks like a duck, talks like a duck, then define it to be a duck.
> >
> >I wouldn't hesitate to tag a cut-and-cover structure as a tunnel in OSM.
> >
> >A passageway through a building (but, say, without being inside that
> >building) is, to all intents and purposes, a tunnel. It doesn't
> necessarily
> >matter whether the "tunnel" is through a brick-built structure instead of,
> >say, a man-made earth embankment or natural hill.
> >
> >By all means expand the tunnel key like others have done with bridge=* to
> >describe the tunnel properties;
> >
> >e.g tunnel = cut_and_cover / tunnel = avalanche_tunnel etc.
> >
> >But I think the key here is that tunnel=yes should be allowable to get the
> >basic meaning across without an editor requiring to be an expert in tunnel
> >construction.
> >
> >Of course there will be edge cases, but we don't have to go and invent a
> >million new keys to describe similar, but not identical, classes of
> object.
> >
> >
> >
>

This may be a stupid way of looking at but its the simlest I see.

All Ways passing Under another Way are tunnels and all ways passing over
another way are bridges.

Why?

Bridges have height restrictions?

Clearly no, the way over the top does not have a height restriction but the
way underneath does. The height restrictions needs to go on the way
underneath not the bridge, which causes the restriction.

On the other hand a tunnel may have a weight restriction which limits
vehicles traveling over the tunnel, it would be stupid to tag the tunnel...

I think the way this is going is that bridges and tunnels should be
relations tagging which way(s) go over/under which other way(s) and what
restrictions apply to what.

The issue here is the difference between a tunnel and a bridge may be not as
clear as it first looks. If someone tags a tunnel as a bridge and it looks
like a bridge then fine, If someone later checks and has good reason to
think its a tunnel really then change it, as long as its correct its fine.
However the tags might refer just as much to the ways passing over the
tunnel as to those passing under it.

Peter
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