[Talk-GB] Maxspeed tagging for the UK

Peter Miller peter.miller at itoworld.com
Sat Apr 9 12:47:48 BST 2011


On 9 April 2011 11:46, Chris Hill <osm at raggedred.net> wrote:

> On 09/04/11 08:20, Peter Miller wrote:
>
>>
>>
>> On 9 April 2011 08:15, Peter Miller <peter.miller at itoworld.com <mailto:
>> peter.miller at itoworld.com>> wrote:
>>
>>
>>
>>    On 6 April 2011 16:53, Ed Loach <ed at loach.me.uk
>>    <mailto:ed at loach.me.uk>> wrote:
>>
>>        Richard wrote:
>>
>>        > I'd put the number for cars (ie 70mph for a dual
>>        carriageway), and
>>        > the source if it's not the number that's on the sign.
>>
>>        This is similar to what I've done. For areas where a national
>>        speed
>>        limit applies I have used
>>               maxspeed= (maximum speed for cars, which is the maximum
>>        maximum I believe, if you see what I mean)
>>        I was also tagging
>>               maxspeed:type=national
>>        or
>>               maxspeed:type=national_dual_carriageway
>>        (no others apply locally). I added these mainly for my use in case
>>        the government ever change the maximum speed for cars on such
>>        roads,
>>        as has been rumoured on occasion in the press, so that I can use
>>        XAPI or JOSM or similar to update the maxspeed values more
>>        easily).
>>
>>
>>    We seem to be nudging towards something close to a conclusion.
>>
>>    Can I suggest that the following two methods are valid, however
>>    the second one should be considered to be 'better' and where it is
>>    used then it should be retained to avoid edit warring.
>>
>>    I have worked a bit on the 'type' tagging to allow it to include
>>    the county which might be GB or UK depending on how Northern
>>    Ireland interprets the rules - is it always the same as the rest
>>    of the UK?
>>
>>    On reflection the convention used elsewhere to put the IT:urban or
>>    whatever into the source:maxspeed tag seems to be misunderstanding
>>    the purpose of source tag which should be for such explanations as
>>    'survey' or 'TfL open speed data' or whatever. Notice that I am
>>    have used 'GB:urban' for the 30mph no sign situation to match up
>>    better with 'IT:urban' etc.
>>
>>
>> I have added some more examples for each method for clarity
>>
>>    Method 1
>>    maxspeed=national
>>    source:maxspeed=survey
>>
>>
>> maxspeed=xx mph
>> source:maxspeed=survey
>>
>>
>>    Method 2
>>    maxspeed=60 mph
>>    maxspeed:type=GB:dual_carriageway (or GB:motorway, GB:rural, GB:urban)
>>    source:maxspeed=survey
>>
>>
>> maxspeed=70 mph
>> maxspeed:type=GB:motorway
>> source:maxspeed=survey
>>
>> maxspeed=60 mph
>> maxspeed:type=GB:rural
>> source:maxspeed=survey
>>
>> maxspeed=60 mph
>> maxspeed:type=numeric sign
>> source:maxspeed=survey
>>
>> maxspeed=30 mph
>> maxspeed:type=GB:urban
>> source:maxspeed=survey
>>
>> maxspeed=30 mph
>> maxspeed:type=numeric sign
>> source:maxspeed=survey
>>
>>  I *hate* the idea that signed speed limits that currently just need
> maxspeed=x would now need two extra tags. That is exactly what I meant by
> think of the mapper. Why should I add extra tags?
>
> I have surveyed an area, added the road type, name, and a source tag, now
> to add a speed limit I need to double the number tags?!? This is ill
> conceived.
>
> My suggestion:
> maxspeed= x mph where it is signed.
>
> maxspeed=national where NSL applies, with
> national=single / dual to distinguish between single and dual carriageway
> limits. Motorways fall out automatically from the highway tag.
>
> Please think of the mapper, and keep it simple. This will also be
> consistent with existing tagging / renderers etc and stands a chance of
> being used.
>

I am not suggesting that you need to go and change anything. I am only
suggesting that if someone 'upgrades' the tagging by doing that work that it
is just fine and dandy and it shouldn't be reverted.

There are not 'two extra tags' anyway. The source:maxspeed tag is good
practice for any tag and can be considered optional for basic mapping.

Lets now consider default values for the maxspeed:type tag to cut down work
further. We could agree that the default value for maxspeed:type is numeric.
We could go further and say that the default value for maxspeed:type for a
single carriageway road with maxspeed=60 mph is 'GB:National' and also that
the default value for motorway and motorway_link with with maxspeed='70 mph'
is 'GB:motorway'. That way the extra tagging is only required in very few
places.

With 'Method 1' however there is much less work for application writers and
less chance that they misinterpret the rules for some country or other and
give out bad data or indeed don't implement that part of the code at all and
the mappers work is wasted. ITO, for example are not about to review all the
rules around the world in order to convert 'IT:urban' into km/h unless it is
made very easy to do.


Regards,

Peter


> --
> Cheers, Chris
> user: chillly
>
>
>
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