[Talk-us] Changeset to revert (or defend

[Val Kartchner]

On Tue, 2010-05-25 at 08:33 -0500, Lord-Castillo, Brett wrote:
> So, the real argument here is what is a bridge and what is a tunnel? Many people considered depressed highways to be tunnels rather than the roads over them to be bridges. I saw USGS topos mentioned earlier. Not all manmade cuts are reflected in topo lines. Manmade cuts that are structures are not considered bare earth and are left out. But then you get to the weird idea of "are the sides of the depressed highway vertical concrete or sloped ground?" and other such criteria.
> --Brett

What I used to distinguish a bridge from a tunnel is to ask, "Is it a
span or a pipe?"  A "pipe" puts (or leaves) the support structure around
the tunnel.  A span puts the support structure under the bridge.  There
will be some places where this becomes ambiguous, but I haven't found
any in my area.

- Val -