[OSM-talk] zones for motorway/in town/outof town?

[Greg Troxel]

  In my part of Australia, we have a speed limit that applies to every
  non-rural street that is not specifically signed as being another
  speed - basically case (b) below.  The wording used in the law is
  "built up area".  (In practice, the test for a "built up area" seems
  to be "does it have street lights?".)

From my experiences in the US and Ireland, I think there are two
distinct concepts for speed limits.

In the US (at least in mass), the speed limit is 30 mph (on unposted
roads) if they are "thicky settled", which is defined:

  "Thickly settled or business district'', the territory contiguous to any
  way which is built up with structures devoted to business, or the
  territory contiguous to any way where the dwelling houses are situated
  at such distances as will average less than two hundred feet between
  them for a distance of a quarter of a mile or over.

and 40 mph on other roads if not divided, and 50 if divided.  In
practice almost higher-speed roads are individually posted.  This sounds
like the Australian situation.

In Ireland, there were signs on all roads leading into villages denoting
a limit inside (50 kph?) and outside (100 kph?).  While it seemed the
signs roughly corresponded to built-up areas, it seemed clear that the
rules were about inside/outside the signs, not about the inter-house
distance.

The tricky part about "thickly settled" is that adding a house can
change the speed limit, with no sign.  But I think that's irrelevant for
OSM purposes.

I think it makes sense to have polygons for formal speed zones, where
one can see signs on the ground.

For other roads, I think it will make more sense to work on a way to
measure prevailing speeds from gpx and upload tags that represent what's
typical.  For residential roads that you don't use to get anywhere,
having the speed tags right for routing doesn't matter much, and for
through roads reality is more important than the posted rules.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 193 bytes
Desc: not available
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20090520/32667b1f/attachment.pgp>