[Tagging] 'ongoing' U-turn restriction

Greg Troxel gdt at lexort.com
Thu Dec 8 14:34:33 UTC 2016

Martin Koppenhoefer <dieterdreist at gmail.com> writes:

> sent from a phone
>> On 8 Dec 2016, at 12:25, Colin Smale <colin.smale at xs4all.nl> wrote:
>> Martin, your interpretation is jurisdiction-dependant. There is
>> sometimes a distinction between single and double lines as well
>> (Queensland is an example I just found). The objectively verifiable
>> fact is the road marking, thereafter you have to interpret the local
>> laws to understand its effect.
> Yes, if you map with the divider tag you don't have to understand the
> meaning, your direct uneducated observation is sufficient for mapping,
> still I'd consider the resulting effect from interpreting the local
> law something "objectively verifiable" as well - and more interesting
> for OSM if there are significant differences in meaning. Usually we do
> add our interpretation (e.g. the access rights of a road, put on the
> highway) rather than limiting us to pure physical facts (e.g. an
> access restriction sign), and we clearly prioritize the former.

I agree with Martin.  In addition, a program computing routes has to
work on semantics, not signs, unless the jurisdiction semantics are
encoded in a separate database.

Also, for routing, what's needed is to compute a route which can be more
or less followed legally by a driver who understands the rules.

Also, for what it's worth, in massachusetts.us, we have two kinds of
solid yellow (center) lines.  One can pass with care give a single line,
but may not cross the line or pass if double.  Except that in practice,
one can pass in a double yellow line zone if the vehicle being passed is
really slow (agriculture or bicycle) or there is some other unusual
situation.   Also, most people who drive here have no idea what the
U-turn rules are :-)
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