[Talk-us] key source:maxspeed

Toby Murray toby.murray at gmail.com
Thu Mar 21 17:30:47 UTC 2013

Part of the issue here is how some countries in Europe sign speed
limits. For example when you cross the border into Austria, there is a
huge sign that lists what all the default speed limits are for various
types of roads. They expect you to remember this. Local speed limit
signs are only posted when the speed limit on a section of road
diverges from the national default.

So for example, at the edge of a town where the speed limit goes from
80 to 100 km/h, the sign is actually an 80 with a slash through it
indicating that the 80 zone is over and you may resume the default of
100 km/h which you remembered from the sign at the border. I believe
this is the implicit vs explicit speed as Martin referred to it. In
Europe they have used the source:maxspeed to indicate if the "source"
of the maxspeed that applies to a given stretch of road is from an
explicit sign or the implicit national default.

Here in the U.S. such implicit speed limits are fairly rare except
within cities where most residential roads are assumed to be 30 mph.
All highways here are explicitly signed with the applicable speed
limit so the established use of the source:maxspeed tag doesn't really
make sense to most Americans.


On Thu, Mar 21, 2013 at 11:44 AM, Ian Dees <ian.dees at gmail.com> wrote:
> On Thu, Mar 21, 2013 at 11:28 AM, Martin Koppenhoefer
> <dieterdreist at gmail.com> wrote:
>> The general usage is according to the wiki:
>> distinguish between implicit and explicit speed limits (i.e. the
>> default maxspeed in the context (urban, rural, motorway) and sign
>> posted limits). The idea is to always add maxspeed=number(unit like
>> mph or kmh) to highways and to distinguish where the limit comes from
>> with the additional key source:maxspeed.
> Since you didn't give specific examples I can't speak in specifics, but it
> sounds like the mapper adding that value for the `source:maxspeed` tag is
> using the tag correctly. They are specifying the source for the speedlimit
> tag. They found the maxspeed value in a PDF somewhere.
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