There is a general "access=<access_type>" tag on Map_Features#Restrictions. There are also a number of "<vehicle>=<access_type>" tags for specific classes of vehicle. However, there is none for "motor_vehicle=<access_type>" because that's the general case, covered by the general tag.
It seems to me that on waterways, where you find boats, "boat" is the equivalent of "motor vehicle". So having "boat=private" seems redundant given that we have "access=private". I suggest deprecating it in favour of the more general tag.
With highways the highway type denotes what the default "vehicle" is for that way:
- Bicycles for highway=cycleway
- Pedestrians for highway=footway|pedestrian|steps
- Horses for highway=bridleway
- Motorvehicles for all other types
Next it is assumed that the default "vehicle" has access unless noted otherwise. This is probably because the mappable roads without access are a minority.
For waterways you get a completely different picture. My guess is that the majority of mappable rivers is non-navigable. Hence the use of boat=yes to denote navigability. The tagging of boat=private is just shorthand for boat=yes plus access=private. You can maybe get this removed from the map features page with this proposal, but I think this shorthand is so convenient, that you will see people keep using it. Therefore any renderer or other application better keep having a "rule" for it.
--Cartinus 23:28, 4 February 2008 (UTC)
I agree with the first half of your logic. But, by analogy, the default "vehicle" on a canal is a boat, and it also has access until noted otherwise. I doubt people are going to tag every waterway=canal with boat=yes, because it's obvious. A canal was built to take boats, just as a road was built to take motor vehicles. <shrug> I guess I don't care too much about this, it just seemed a consistency cleanup.
Gerv 09:21, 16 February 2008 (UTC)
I don't agree that access=* implies motor vehicles. In fact, to me it implies all vehicles(+pedestrians and equestrians). Any exceptions must be explicit. For waterways, consider a swimming area, which might be boat=private, swimming=permissive (Leaving aside that there is no key 'swimming' as yet, I assume you take the point). The only reason that there is no access key for motor_vehicle is that no one has seen a need for it, presumably because all the roads that do not allow motor vehicles are other special classes (like bridleway)
--Hawke 22:19, 18 February 2008 (UTC)
OK, then. Proposal abandoned.
Gerv 18:33, 5 March 2008 (UTC)
...is not open yet.