[Talk-GB] inferred single-carriageway NSL?

[Peter Miller]

On 16 March 2011 18:58, Richard Bullock <rb357 at cantab.net> wrote:

>
>  In summary, this little tag is much less simple than it may appear at
>> first
>> glance! I am very interested in getting a fuller set of this data into
>> OSM.
>> Thanks for the 'pedantic' examples of 60mph limits on dual carriageways.
>> Being pedantic back can anyone demonstrate the existence of a 60 mph sign
>> on
>> a single carriageway road?
>>
>
> I can certainly do that. I believe this one was places to "remind" drivers
> that, despite having four lanes, it's still a single carriageway and =>
> 60mph max
>
> http://tinyurl.com/6x5u4la
>
> In this case, it's probably technically "national", but specifically signed
> at 60.
>
> I know of a couple of examples of cases on a dual-carriageway where it's
> specifically signed 70mph AND most definitely not the national speed limit.
>
> http://tinyurl.com/66pucm7
>
> curious. I know that there was a proposal recently to replace all
'unrestricted' signs by numeric signs to reduce confusion.


> The reason it's not the national speed limit, is because of the way that
> the legal orders that created this stretch of road were drawn up. In this
> particular example, this type of road has no national speed limit - and a
> white sign with black diagonal line would mean genuinely derestricted. (It's
> a non-motorway special-road in case you're asking - and special-roads only
> have a national speed limit if they are also motorways - hence a specific
> 70mph speed limit order had to be drawn up).
>
> Back to the point in question, however;
>
> Do we *really* need to be tagging national speed limits on individual ways?
> E.g. the vast majority of roads ought to be one of;
> *residential roads subject to 30mph
> *rural roads subject to NSL
>
> (I realise a lot of councils have been cutting lots of roads from NSL -> 50
> in recent years, but I'm sure NSLs outnumber 50s on the whole)
>
> Perhaps we could tag the ones that differ from the above - and let
> post-processors add national defaults as necessary?
>
> Taken to its extreme, are we going to bother adding surface=paved to every
> motorway, motorcar=yes to every road?
>

I think it is reasonably to assume that motorway are paved, that most road
types can be used by car and that two-way roads have 2 lanes unless
otherwise stated and that residential roads are 30 mph unless otherwise
stated for the time being. Having said that a lot more 20 mph limits are
possibly on the way. In time we might wish to me more explicit about more
road classes.

As an example I am tagging two-way roads as lanes=2 to make it clear that I
have checked them and they are indeed definitely 2 lane.

I suggest that we focus on tagging tertiary roads and upwards for speed
limits for now as well as any 20 mph zones.

The maxspeed wiki page does request that maxspeed is a number and not just
'national' or whatever which I think makes sense given the number of
countries and rules and details of how the rule are defined and how they
change over time.



Regards,


Peter


>
> _______________________________________________
> Talk-GB mailing list
> Talk-GB at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk-gb
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk-gb/attachments/20110316/b882cd5f/attachment-0001.html>