[OSM-talk] Bridges

[David Earl]

> On Saturday 14 October 2006 18:03, Tom Chance wrote:
> > On Saturday 14 October 2006 17:41, David Earl wrote:
> > > Why is highway=bridge a property of a node not a linear segment which
> > > covers the extent of the bridge (on a segment, like abutters, so it
> > > doesn't mean breaking up a way)? Railway bridges are linear but road
> > > bridges aren't.
> >
> > So far as I understand it, highway=bridge is for when a node is a bridge
> > (not sure when that would be), and bridge=yes is for when a segment is a
> > bridge. This is so you don't get two values for highway (bridge and
> > primary, for example). That's just my guess, anyway.
lems would
I really should read to the bottom of the page...

> Sorry, I meant when a way is a bridge, since segments are
> potentially being
> phased out.

That's awkward, because you'd have to break a Way into 3 parts to represent
the bridge and the bits either side of it.

I'm too recent to have seen the discussion you've presumably had re removing
segments, but presumably you're considering having a Way composed of just a
series of node references. It does seem like an anomaly to have bridge=yes
on a segment when the Ways are the significant mapping entities. Maybe it
could be done like this:

  <way id='3665608' timestamp='2006-10-13 20:40:33'>
    <node id='14563115' />
    <node id='14563116' />
    <node id='14563112' />
    <node id='14563113' />
    <node id='14563114' />
    <tag k='highway' v='residential' />
    <tag k='name' v='Fulbourn Road' />
    <part k='bridge' v='over'>
      <node id='14563112' />
      <node id='14563113' />
    </part>
  </way>

In a sense this puts a new kind of segment inside a way, but only where it
is needed. Could apply to lots of linear roadside features as well.

David