[Tagging] access in the wiki: move psv to "by use"

[martinq]

Hi,

>         I propose to move "psv" (including "taxi" and "bus") from the
>         vehicle classes section to the section "by use", because that's
>         what it is.

maybe that is what it should have been in the past.

Sadly the actual use in real world tagging seems to interpret "bus" also 
as vehicle category (means the vehicle is registered as "bus", in Europe 
class M2 or M3). Example: 3000 uses of maxspeed:bus, I am pretty sure 
these uses refer to vehicle category and not the use...

See also 
http://wiki.openstreetmap.org/wiki/Talk:Key:access#Bus_has_multiple_meanings 
for an older discussion on the meaning of "bus". There was no final 
agreement.


Possible solution:

"use/purpose" goes into the value, as we have already done it in 
"agricultural" or "forestry" (agricultural=* means vehicle type, 
*=agricultural means agricultural use), the key gets a vehicle category:

bus=* refers to a vehicle registered as "bus"
*=public (or "public_transport", which is clearer but longer) if the 
vehicle in the key is used for public transport (public access, driving 
with strangers, no private negotiation needed)

Example:
bus=public_transport -- a registered bus is only allowed to access if it 
is used for public transport, excluding for example rented tour buses.
bus=yes -- all registered buses can access, including hired buses

Obvious issue: 200,000 uses of "bus"...

Further refinement, e.g. bus:m2 or bus:m3, is possible, but I hardly see 
any need for this.

--

Similar for taxi:
taxi=* refers to vehicles registered as taxi.
*=taxi (or taxi_service for clarity) refers to the use as taxi

Examples:
vehicle=taxi(_service) --> Only vehicles providing taxi service (no 
matter if small buses or special passenger cars) can access, so empty 
taxis cannot pass

taxi=taxi(_service) --> Only vehicles registered as taxi AND providing 
taxi service can access

taxi=yes --> Vehicles registered as taxi can access, including "empty" 
taxis without passengers


Also here further hierarchical refinement is possible, e.g. taxicab and 
taxibus, but I do not see the need for this at the moment.


There is a drawback of the "use in values" approach, but only for rare 
cases:

1) There is still no supported/accepted way to tag multiple values for 
the same key. But the more values we define, the more likely the demand 
for multiple values.

2) If other restrictions (maxweight or - more precisely - maxgcweight, 
maxgcweightrating or maxactualweight) are made conditional, we need an 
update of our conditional tagging, for example by introducing "use":

A maximum weight rating of 7.5 for everyone except public transport bus 
or agricultural traffic
maxgcweightrating=7.5
maxgcweightrating=none @ use=agricultural
maxgcweightrating:bus=none @ use=public_transport

martinq