[OSM-talk] Divided roads proposal

Steve Bennett stevagewp at gmail.com
Thu Dec 3 10:30:09 GMT 2009


On Thu, Dec 3, 2009 at 9:17 PM, Richard Mann
<richard.mann.westoxford at googlemail.com> wrote:
>> That's a problem with the rendering, not with the mapping.
>
> Unless you want to write routines for pre-processing two almost-parallel
> ways back into a single way so it can be rendered neatly, I suggest it's a
> mapping problem.

Yep, a very hard rendering problem, or an easy mapping problem.

> Everything about a dual carriageway can (now) be expressed using turn
> restriction relations, and it would probably be better if it were done that
> way.

I don't want to be as ambitious as genuine dual carriage motorways,
but it would be great for minor roads.

Here's an example I came across (I didn't map it):

http://www.openstreetmap.org/?lat=-37.824316&lon=144.940393&zoom=18&layers=B000FTF

See Hartley St there? It's a tiny pathetic service road that happens
to have some concrete blocks down the middle of some sections. I can
just picture how nicely this would render with the right tagging and
styles...

Another example, nearby:
http://www.openstreetmap.org/?lat=-37.81993&lon=144.960348&zoom=18&layers=B000FTF

Queensbridge St, where it splits from the bridge itself. The two lanes
are actually separated by a decent chunk of concrete. The northbound
lane then splits again just before hitting Flinders St. I don't blame
the mapper for not representing all this detail, because ultimately it
doesn't really make a difference to anyone using the map, and it will
render as a mess.

Another really cool thing you could do with this proposal (not
currently suggested) is a width parameter. Then you could really
precisely control the separation of the lanes, which are now a bit hit
and miss - it's very hard to specify how much gap there is, because
you have to guess how wide the renderer will think the road is, then
compensate for that.

Steve




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