[OSM-newbies] Highway Types and Speed Limits

[David ``Smith'']

I think I have a half-formed idea about how to solve this dilemma
about standard maxspeeds.  First, tag what the maxspeed is, so
applications that use the data have something to look at.  Then, make
another tag, which would look something like
maxspeed_basis=US:OH:interstate .  And then there would be some
repository of standard speed limits somewhere.  That repository would
contain an entry called US:OH:interstate, whose value would be 65 mph,
because that's the current standard speed limit for Interstate
highways in Ohio.  If the Ohio General Assembly then increases that
speed limit to 70 mph, then we update the value in the repository.
Any applications using the data which are aware of the maxspeed_basis
tag can then use it to find the correct maxspeed value*.  Then, to
take care of less-informed users of the data, a script can be run to
update all ways with maxspeed_basis=US:OH:interstate to have
maxspeed=70 mph.

*In this system, the value determined by looking up a maxspeed_basis
should take precedence over a literal maxspeed value in any
application capable of performing such a lookup.  If any way has a
maxspeed that should be used regardless of any standard value, then it
simply shouldn't have a maxspeed_basis tag.

The reason why I call this a half-formed idea is I haven't come up
with a good manner in which to store the repository.  It could be
stored as tags on a special relation with a published ID and no
members; then it would be accessible via the OSM API, but the misuse
of a relation makes this solution hackish and ugly.

-- 
David "Smith"
a.k.a. Vid the Kid
a.k.a. Bír'd'in

Does this font make me look fat?