[Talk-GB] inferred single-carriageway NSL?

[Peter Miller]

On 15 March 2011 14:56, MarkS <OSM at redcake.co.uk> wrote:

> Is this because roads with a national speed limit don't have a single
> maxspeed. For example a motorway has a maximum speed of 70mph for some
> vehicles and 60mph for others.
>
> Thus tagging a motorway with say "maxspeed:70mph" (and no other speed
> related tags) doesn't fully represent the speed for all vehicles.
>
> I'm guessing therefore that where roads are tagged this way he is trying to
> setup tags to indicate that 70mph may not be the complete picture and that
> 70mph is taken from national speed limit (the source tag) but that this
> needs checking (the Fixme tag).
>

Mopeds are speed limited to 30mph and there are lots of different maxspeed
rules for other classes of vehicles. See Wikipedia article for all the gory
details
http://en.wikipedia.org/wiki/Road_speed_limits_in_the_United_Kingdom

My understanding is that the signed speed limits are those that must be
obeyed by those classes of vehicles that are not limited by some other rule.
I don't consider that we need to do more that we are which is to reflect the
street sign in the data.


> It could be that case that once it has been checked he is expecting
> something more like maxspeed:national to be used.
>
>
> Certainly, I can see that in the areas round me the "maxspeed:60mph" ways
> have been updated by him, but the "maxspeed:national" haven't.


Same here. Incidentally, I have been updating maxspeed:national to either 60
mph or 70 mph as appropriate in various places over the past week by hand
and sorting out other tagging issues.

I would love it is a bot could find all the occurrences of '30 Mph' and
convert them to '30 mph' etc.

Also, occurences of '30's (ie 30 km/h) in the UK which can reasonably be
deeded to be '30 mph'. Slightly tedious to do by hand.

Also there are many occurrences of speed of around '48.2' which can
reasonably confidently be treated as '30 mph' and other obvious speed
ranges.

Then there are the '30mph' which should for consistency be '30 mph' (with a
space).


Finally, I have a technical question on speed limits. What exactly is a dual
carriageway? Are the slip-roads between two dual carriageways also dual
carriageways (and therefore have 70mph limits) or are they not and are they
therefore 60mph limits? Similarly for short sections where a single
carriageway road divides for a short section.

A technicality for sure, but I find myself being a bit arbitrary in these
cases.

Regards,



Peter




>
>
> On 13/03/2011 12:27, Dave F. wrote:
>
>> Hi
>>
>> You've probably seen the numerous edits by chriscf. Can anyone explain
>> the purpose of these edits & what the the tags below even mean?
>> I've had no reply to an email sent to him a couple of days ago
>>
>> In my locality, each of his edits already had a maxspeed (with units)
>> tag accurately mapped by people on the ground. I don't understand what
>> these extra tags add to the OSM's quality
>>
>> I'm most concerned about the 'inferred' references, which, to me, is no
>> better than guessing; something that should not be a part of OSM.
>>
>> Comment: units in speed limts, add/remove special road status, attempt
>> to infer NSL status
>>
>> Tags:
>> FIXME:nsl = inferred single-carriageway NSL - remove this tag once
>> verified
>> source:maxspeed = UK:nsl_single
>>
>> Cheers
>> Dave F.
>>
>
>
>
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