[OSM-newbies] Highway Types and Speed Limits

[Andre Engels]

On Thu, Oct 15, 2009 at 6:00 PM, Stefan Monnier
<monnier at iro.umontreal.ca> wrote:
>> When I'm tagging say, a residential street, should I also be tagging the
>> 30mph speed limit that the residential street implies (at least in the UK)
>> or should I only tag if the street has a non-standard speed limit such as 20
>> or 40mph?
>
> I think the rule should be something like:
> - if the road has no speed-limit sign, then it's wrong to tag it with
>  the default speed limit for this kind of road.
> - if the road has a speed-limit sign and it's different from the default
>  spped limit for this kind of road, then it should ideally be tagged.
> - if the road has a speed-limit sign and it's the same as the default
>  speed limit for this kind of road (i.e. that limit could be guessed
>  even if the sign wasn't there), then it's good to tag it, but it's not
>  that important.

I disagree. I think standard speed limits can also be useful to
include, for several reasons:
* to denote to other volunteers whether someone has bothered checking
the speed limit already so that when five people are checking speed
limits in the same region, they are not all checking the same roads
* because default speed limits vary by jurisdiction
* because people may differ in the way they map their regional highway
types onto the ones of Openstreetmap, so that two roads may both have
the default speed limit for their type of road, and have the same
classification, and yet have different speed limits
* because speed limits on the same type of road may differ - in
particular they are often lower in cities and towns than on the
countryside


-- 
André Engels, andreengels at gmail.com