[talk-au] maxspeed - best practice?

[Leon Kernan]

Most software will make assumptions about the max speed based on road type
if it's not specified (for better or worse).
Having it recorded is still the best way if known though.

Also today, Vicroads has announced that speed zones will be changing
around Victoria again. Getting rid of 70's and 90's this time.
Keeping up with the changes is a full time job.

On Tue, Aug 14, 2012 at 4:44 PM, Ian Sergeant <inas66+osm at gmail.com> wrote:

> Hi,
>
> a) The thing is, if you don't tag maxspeed=50, then how do tell a
> residential road that is known to be maxspeed=50, against one that is just
> un-surveyed, and might be maxspeed=30,40 or 60?
>
> c) source:maxspeed=sign is clearly correct if there is a sign. If you've
> surveyed around an area, and there isn't a sign, personally I'd tag
> source:maxspeed=survey.  The alternative here, would be
> source:maxspeed=default or some such, but given our history of tagging
> "site unseen".   It  I think this is best avoided. Same goes for
> source=implied for the same reason.  If you've visited and determined the
> speed limit, it is a survey.   maxspeed=local_knowledge if you drive around
> the residential streets in your area all the time, and you just know they
> are all 50km/h.
>
> Just an aside,  a simple case study in presumptions.  Probably the most
> popular OSM open source router is OSRM.  The speedprofiles for that project
> you can see here
>
> https://github.com/DennisOSRM/Project-OSRM/blob/master/speedprofile.ini
>
> I believe OSRM will use a maxspeed on a street if it finds one, so once
> you start marking maxspeeds it makes sense to mark others around them,
> otherwise a maxspeed=40 road will become a preferred road over other
> residentials and secondaries.
>
> I'm sure the motivation for tagging all residentials as maxspeed=50 was
> partly an attempt to address this issue.
>
> Of course, there is a good argument for this being fixed in OSRM, or in
> post-processing the AU data, etc.
>
> Ian.
>
>
> On 14 August 2012 15:30, Ben Johnson <tangararama at gmail.com> wrote:
>
>> In regards to residential areas - I remember last year there was some
>> talk about the bot that added "50" with the (incorrect) "maxspeed:source"
>> key = "default residential speed limit in Australia"  and I think there was
>> consensus in the local community that this was a mistake.
>>
>> With remapping some of my local areas, I'm now curious what's best
>> practice in Australia is for tagging maxspeed on residential streets.
>> Specifically...
>>
>> a) is it even necessary or desirable to explicitly define maxspeed for
>> every residential way - or should we just presume any highway=residential
>> is maxspeed=50, unless otherwise stated?
>>
>> b) if presumptions do exist, should 50 zones on tertiary and unclassified
>> ways be explictly tagged ?
>>
>> c) if tagging maxspeed on every street, in respect to source... does a
>> simple source:maxspeed=sign suffice for the "general area" or only for the
>> specific way on which the sign is placed?  I notice these residential 50
>> speed signs are often on tertiary streets, or gateway points into general
>> residential areas.  Side-streets obviously share the 50 limit, but are
>> mostly not signposted. Do we need a new standard source value like
>> source:maxspeed=implied for the side streets ?
>>
>> Sorry if I'm re-covering old ground - I'm just not sure where it was
>> left... if anywhere!
>>
>> Thanks in advance.. BJ
>>
>>
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>
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