[Tagging] Zone 30 (maxspeed)

Sebastian Klein bastikln at googlemail.com
Wed Jul 7 09:15:34 BST 2010


Colin Smale wrote:
>  On 06/07/2010 21:02, Ulf Lamping wrote:
>> Am 06.07.2010 20:38, schrieb Colin Smale:
>>> On 06/07/2010 18:44, Richard Mann wrote:
>>>> I'm not really clear what is the value of tagging a "zone", except in
>>>> a note. Why not just use the standard maxspeed tag?
>>>
>>> +1
>>>
>>> Here in NL it warns you that the given road sign (could be maxspeed,
>>> could be some other restriction) is valid "until further notice" i.e.
>>> until you leave the Zone. Without the Zone indication the restrictions
>>> lose their official validity at the next junction, which leads to speed
>>> limits etc. having to be repeated very frequently. So it is really only
>>> a shorthand notation to save money on signs and to reduce the clutter of
>>> street furniture. The default speed limit in built-up areas is 50kph so
>>> that actually rarely needs to be signed at all. But to make an area
>>> limited to 20kph means it has to be signed explicitly.
>>>
>>> It sure would make life easier if you could just draw a (temporary)
>>> polygon and get Potlatch to set maxspeed=20 on all enclosed roads 
>>> though...
>>
>> Well, no. Two different things here:
>>
>> a) What's the actual maxspeed value
>> b) What's the cause of the actual maxspeed value
>>
>> Wether b) needs to be tagged or not is a matter of personal opinion - 
>> further discussions on this are therefore pretty much pointless ...
>>
>> It was a long and hard discussion on talk-de that b shouldn't be 
>> replacing a altogether - I'm personally very glad that this concensus 
>> was made.
>>
>> If someone want's to specially tag b), I don't see a reason not let 
>> him do it that way. I'm not doing it but it won't harm anyone and will 
>> save us from ongoing discussions if we want to tag the actual value OR 
>> the inherent cause of it (sign, zone, ...).
>>
> Despite your opening sentence we agree. I was trying to make clear that 
> there is nothing special about the actual max speed in a "30 Zone", only 
> the way it is signed on the ground is different (for reasons I 
> explained). 

Well, almost. Example for German laws for "30 zone":
* Obligatory bicycle paths (sign 237 and 240) are forbidden, so as a car 
driver you have to be more wary of bikes on the street.
* The right of way is always right before left (no traffic lights or 
priority roads), so depending on your driving style, this might speed 
you up or slow you down.

Also it could be a good idea to give a negative bias for routers as 
these zones are usually residential areas not intended for through traffic.

> So IMHO all ways should have their maxspeed indicated 
> individually in the traditional way, and if someone wants to draw a 
> polygon to indicate the limits of the zone, well, OSM won't stop them. 
> The polygon I was talking about was only a simple way of selecting a 
> whole bunch of streets in one go with the intention of making a simple 
> edit (e.g. add maxspeed=30) to all of them as I can see the manual 
> one-by-one method getting rather tedious. As John Smith mentioned, there 
> appears to be some support in JOSM for this.

See [1] for the reasons why we don't use polygons for traffic zones. 
(Note that contrary to what is found on this wiki page, maxspeed=xx is 
always tagged explicitly in the traditional way and never implied by 
other tags.)

[1] 
<http://wiki.openstreetmap.org/wiki/Proposed_features/trafficzone#Frequently_asked_questions_.28FAQ.29>

--
Sebastian




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