[Talk-GB] maxspeed field - what units should we use. etc

[Peter Miller]

On 4 Jun 2009, at 17:11, WessexMario wrote:

> Robert Naylor wrote:
>>>> On Thu, 04 Jun 2009 11:13:28 +0100, David Earl
>>>> <david at frankieandshadow.com> wrote:
>>>>
>>>>
>>>>> I also came across someone tagging maxpeed=NSL yesterday. If it  
>>>>> gives
>>>>> someone happiness, fine, but I don't really think it should be
>>>>> necessary
>>>>> to tag the default situation, only when there is an exception to  
>>>>> the
>>>>> general rule
>>>>>
>> This page seems to confirm this:
>> http://www.abd.org.uk/know_your_speed_limits.htm
>>
>>
> There is a major problem with using maxspeed=NSL.
> Dual Carriageways.
> How will the applications know that a way is part of a dual  
> carriageway
> or is just one oneway way that happens to be near another oneway way?

Here is a proposal for using relations to combine carriageways and  
also one for collecting together all the slip-roads into a single  
feature called 'junction':-

"To avoid duplication, the name/ref of the street should continue to  
be placed on the Ways of the street or in the Relation for the  
collected ways of a street. This relationship is only intended as a  
hint to renderers that the adjacent ways are actually part of the same  
street/road so the name could be positioned between the carriageways  
rather than in both, or the road number rendered only once for  
adjacent pairs of ways and similar applications.
http://wiki.openstreetmap.org/wiki/Relations/Proposed/Dual_carriageways

And this one for interchanges
"The main purpose of the Relation at present is to give renderers or  
route planners a name and or number for a junction. It also means that  
a staggered cross roads controlled by linked traffic signals can be  
grouped into the one junction while still maintaining the geometry of  
the streets correctly.
http://wiki.openstreetmap.org/wiki/Relations/Proposed/Junctions


Regards,


Peter


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