[Tagging] Clarify tag access doc

[Kytömaa Lauri]

Rob Nickerson wrote:
>Although I don't know the history of the access 
>tag, I would expect that "designated" and
>"permissive" might have something to do with 
>Public Rights of Way in the UK:

Just a recap on how the values have evolved,
not to open the "path controversy", but just to 
give some background:

'Designated' is a result of the path controversy.

Back in 2008, or thereabouts, there was only
yes, permissive, destination, private, no.

Permissive is (originally, in the OSM sense) a UK thingy,
as it seems to matter there. Back then very few used 
the tag designation=*, if any. Apparently, it's easier
there for a land owner to legally limit outsiders from 
using any road on their property (no matter how big), 
unless it's legally designated as a public highway (or 
any of the other designations) - in other words "it's
a right of way", as it's described at Key:access.

There was no need for designated or official; either
- you have a right to use a way, or
- the land owner has given a general allowance for 
   anybody, or
- you have a right to use a way, but only if your 
destination is along said way, or
- you can use the way if you really know the owner
   allows you specifically to use it.
This was thought to be sufficient for any case.


When some non-UK mappers felt that 
highway=cycleway + foot=yes somehow "prefers"
or favours cyclists over pedestrians, they suggested 
highway=path.

x=designated was originally meant solely to record 
_for which users any such highway=path is_ 

(where x=foot/bicycle/snowmobile/hazmat/whatever,
but not access=designated).
Generally this is always somehow signposted; if it's
not signposted, the way looks and works like a 
footway/cycleway/track or any other highway, and
could be tagged as such.
Without at least one tag x=designated, one can 
tell very little about the form and practical use of 
any single highway=path.

Some months later, users in Germany, iirc, noticed
that new mappers had used the value 'designated' 
where there was no specific traffic sign (i.e. the 
blue "compulsory use" kind), so they started using
x=official and defined it solely as:

"official = has a compulsory use traffic sign for that 
transport mode"

Tool/rendering support for x=official is less common,
than the support for =designated.


Later, mappers noticed that besides agricultural=yes
("tractors allowed/not allowed"), sometimes a traffic
sign "no motorvehicles" has a supplementary sign
"agricultural traffic allowed", to allow those maintaining
the farm fields along that road to use any vehicles
they need to. Hence, there's the value 'agricultural',
most likely used with vehicle= or motor_vehicle=.
Both agricultural=* and motor_vehicle=agricultural
have about 18 000 uses.

Likewise, there's apparantly a lot of "no motor 
vehicles, but allowed for forest maintenance" signs 
somewhere. So they've used x=forestry.

I don't remember exactly when was 'delivery' added 
as a value, but that's not one of the "original" values,
either. Deliveries can happen with any vehicle, but 
it's not a general allowance for destination traffic;
like agricultural, forestry and customers, it's a "role",
as the various proposals for describing complex
access restrictions would label these. 

Roles don't belong in the value, IMO:
motor_vehicle=customers;delivery;garbage_hauling.

(I've seen one place with a sign "no motor vehicles, but 
dog park waste collection allowed." After that dog park 
there's a regular 'combined cycle/footway' sign. 
Effectively, even the first part is a cycleway).


-- 
Alv