[Tagging] maxspeed:signed=no - new proposed tag
Minh Nguyen
minh at nguyen.cincinnati.oh.us
Tue Jan 5 01:46:25 UTC 2021
Vào lúc 15:43 2021-01-03, Martin Koppenhoefer đã viết:
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> sent from a phone
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>> On 3 Jan 2021, at 22:17, Mateusz Konieczny via Tagging <tagging at openstreetmap.org> wrote:
>>
>> (1) we have no tag for "there is no maxspeed signage applying here"
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>
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> we do, source:maxspeed is about this
source:maxspeed=* seems capable of indicating the presence of a default
speed limit, since apparently the "<country_code>:<context>" syntax is
only for unsignposted speed limits. [1] But in the scenario Mateusz
describes -- an intrepid surveyor tags a street beforehand to flag it to
armchair legal analysts -- how would the surveyor know which context to
assign? Also, wouldn't it be strange to see source:maxspeed=* on a
feature without maxspeed=*?
The "<country_code>:<context>" syntax is also overly simplistic. It's
telling that no one has attempted to extend the table at [2] with values
for the U.S. Each state has plenty of default speed limit contexts, some
of which defy the OSM tagging model. [3]
There seems to be significant usage of *:signed=no for things like
maxweight, opening_hours, and name, so extending the scheme to maxspeed
seems obvious to me. If the legal analyst bot can find-and-replace
maxspeed:signed=no with the appropriate maxspeed=* and source:maxspeed=*
afterwards, so much the better.
>>
>> (3) tagging exact max speed is often de facto impossible as it
>> requires remembering that there are separate rules for ...
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> impossible? You have to know the local rules, that’s far from impossible, it’s rather a requirement that you can safely drive on these roads.
Not everyone who surveys for OSM does so behind the wheel or even has a
driver's license. Not many data consumers can consult a local licensed
driver for the correct answer on demand. ;-)
Even someone who does drive may not have a full grasp of default speed
limits in their jurisdiction. Where I learned to drive, default speed
limits are the norm in rural areas and some suburbs, but even the
official driver's handbook that you're required to familiarize yourself
with [4] doesn't capture the whole default speed limit decision tree. [5]
[1]
https://wiki.openstreetmap.org/wiki/Special:PermanentLink/2084425#How_to_tag
[2]
https://wiki.openstreetmap.org/wiki/Special:PermanentLink/2084425#Context_Specific_Values_.28Default_Limits.29
[3]
https://wiki.openstreetmap.org/wiki/Talk:Default_speed_limits#California_business_districts
[4] https://publicsafety.ohio.gov/static/hsy7607.pdf#page=45 (p. 41)
[5] https://wiki.openstreetmap.org/wiki/File:Speed_limits_in_Ohio.svg is
even a simplification
--
minh at nguyen.cincinnati.oh.us
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