[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:
> sent from a phone
>> 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"
> 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 ...
> 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]

[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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