[Talk-GB] Maxspeed tagging for the UK

Peter Miller peter.miller at itoworld.com
Wed Apr 6 15:55:59 BST 2011

On 6 April 2011 15:02, Chris Hill <osm at raggedred.net> wrote:

> On 06/04/11 14:22, Peter Miller wrote:
>> Do we have a preference for tagging unrestricted limits in the UK? I say
>> that because a section of the A1 is beginning to look a bit war damaged  (as
>> in edit war).
>> It started with maxspeed=national. I changed it to maxspeed=70 mph.
>> Christcf then added a 'source:maxspeed = UK:nsl_dual' and also 'FIXME:nsl =
>> inferred dual-carriageway NSL - remove this tag once verified; if this is a
>> Special Road, remove the source:maxspeed tag and add motorroad=yes'. And now
>> c2r has changed maxspeed back to national!
>> Here is the way in question:
>> http://www.openstreetmap.org/browse/way/3994397/history
>> My preference is to put a numeric speed in the maxspeed field and
>> something like 'UK:nsl_dual' in source:maxspeed field, however I am not that
>> keen on a prolonged edit war on this and want to gauge wider opinion.
>> If it is ok to put something like 'national' in the maxspeed field then
>> what text options are appropriate for the UK? 'national' seems too vague.
>> 'UK:national' or 'GB:national' would fit with the recommended structure as
>> would 'UK:motorway', 'UK:nsl_dual' and 'UK:nsl_single' however I can find no
>> guidance on that.
>> Assuming we are supporting these second format then where should the
>> look-up table be that gives the values? This page is having a go at it but
>> doesn't seem to be doing a very good job!
>> http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed
>> Incidentally, I have also updated the key:maxspeed wiki page so that it
>> more clearly represents the tagging recommendations and options available,
>> in particular it presents the two options for encoding implicit speed limits
>> well. Can people see if they agree with current representation of opinion.
>> http://wiki.openstreetmap.org/wiki/Key:maxspeed
>> Any thoughts?
>>  I think we should tag what we see on the ground. The sign is national
> speed limit, not 60 or 70 mph. The black & white sign does not mean 60 mph
> or 70 mph for every vehicle, lorries have lower limits for example. I
> currently don't tag maxspeed on national speed limits, but this absence
> encourages the nonsense that chriscf came up with, so if pushed I'd use
> maxspeed:national . All of the roads being discussed are in the UK, so they
> do not need UK: or GB: namespaces. This is a geo-database after all.

I have a number of concerns:

1) We have no agreement on maxspeed tagging in the UK which means there is
potential for edit warring as we have seen on the A1 which will discourage
further work.

2) Our use of 'national' doesn't fit within schemes being used in other
countries which suggest a two letter country code first. UK:national would
be a recognition that this is an issue and would avoid the need to accurate
borders for all countries which is I assume why the two letter code has been
adopted in the first place.

3) There is no established mechanism that I can see to turn the 'national'
text into a numeric speed even if one does know that it applies to the UK
(similarly for a value of BE:motorway incidentally).

4) If the same text (for example 'national') is used for motorways, dual
carriageways and single carriageways then it seems to be very difficult to
establish if one is talking about a one-way street that happens to also be a
primary or trunk road (and should therefore be 60 mph) or if it forms half
of a dual carriageway (and should therefore be 70 mph). The only reliable
method is to look for a parallel way next to the way in question with same
ref, the same class and the opposite direction. Decisions relating to slip
roads is also troublesome and will vary by country.

5) With reference to the fact that not all vehicles are allowed to travel at
the maximum speed then that also applies to 50mph and numeric 60 mph limits
where some vehicles (such as mopeds) cannot legally travel at those speeds.
How do you suggest that these should be tagged?

All in all, speed limits tagging still seems pretty flakey which is a shame!



> --
> Cheers, Chris
> user: chillly
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