[Talk-GB] Maxspeed tagging for the UK
peter.miller at itoworld.com
Thu Apr 14 12:41:57 BST 2011
On 14 April 2011 12:27, Chris Hill <osm at raggedred.net> wrote:
> On 14/04/11 11:42, Richard Fairhurst wrote:
>> Peter Miller wrote:
>> > So the proposal is now:
>> I may be missing the point on all of this, but:
>> Why are we doing this?
>> In OSM we optimise for the mapper, not the data consumer. That means we
>> exceptions, not majorities.
>> So if you have highway=motorway, the consumer can assume the national
>> limit applies, which is 70mph; no need for a maxspeed or maxspeed:type
>> If you have highway=trunk (or anything down to unclassified), assume the
>> national speed limit applies, which is currently 60mph if it's a single
>> carriageway, 70mph if it's a dual. And so on.
>> Where this isn't true, you put a maxspeed tag on. This works for pretty
>> everything from 30mph on B roads through villages to 50mph on rural A
>> to 70mph on the A55 Special Road. No need for a maxspeed:type tag at all.
>> Have I missed something blindingly obvious?
>>  Perhaps the only difficulty is that there's currently no trivial way
>> identify what's a dual carriageway and what isn't, short of doing clever
>> geometry stuff. But that's easy to fix: either a relation (spit) or
>> preferably something simple like dual_carriageway=yes.
There would be a number of benefits of wrapping dual carriageways up into a
relation saying 'these two ways are part of a single dual-carriageway'. One
is to get round the maxspeed problem, but it also provides information
needed to create overview mapping with a single way for a dual carriageway.
Here is one I created some time back (a long time back actually, it is
I was also interested in wrapping all of the ways that make up a junction
into a 'interchange' relation. Again, here is one I made earlier.
In response to Richard - thanks, that is a good example. Here is the
equivalent page for maxspeed which has lots of information in it but is way
off being useful to a parser! 
> Cheers, Chris
> user: chillly
> Talk-GB mailing list
> Talk-GB at openstreetmap.org
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