[OSM-talk] [tagging] Current access rules

[Dave Stubbs]

On Sat, Jun 28, 2008 at 4:20 PM, Ben Laenen <benlaenen at gmail.com> wrote:
> On Saturday 28 June 2008, Dave Stubbs wrote:
>> On Sat, Jun 28, 2008 at 1:10 PM, Ben Laenen <benlaenen at gmail.com>
> wrote:
>> > I'm getting issues with the fact that access rules are never
>> > formally defined. For example, does this make a oneway road
>> > accessible for bicycles in two directions or not:
>> >
>> > oneway=yes
>> > bicycle=yes
>>
>> No, it doesn't.
>> It says bicycles are allowed on the road.
>
> Well, you must understand the problem that this is nowhere described how
> multiple tags work together. This is just your interpretation. I see
> for example the Key:access page and I read that bicycle=yes means that
> bicycles have access, with no legal restrictions.

Hmm... "with no legal restrictions" is the problem here. It doesn't
say that, and certainly isn't how I've ever thought of it.
It doesn't say anywhere in access tags that they have any bearing on
onewayness at all. As far as I can tell oneway and access are
completely unrelated tags. access tags determine what vehicles are
allowed, and oneway/max_speed determine what they can do.

So yes, it's interpretation, but a fairly logical one. I think you've
been thinking about the problem too much ;-)


>
> And there are lots of small problems like this. If we want osm to be
> usable for routing, we need to have the formal definitions of each tag.
> So again, I invite everyone interested to
> http://wiki.openstreetmap.org/index.php/Proposed_features/Access_restrictions
> so we can finally fix this thing.
>
>
>> > For those saying that it doesn't, how would they propose a tag for
>> > allowing bicycles in two directions
>>
>> cycleway=opposite
>
> As you mention, it can't be extended to arbitrary vehicle types.
>
> That said, we could define cycleway=opposite and not try to look for
> simple tags for other vehicle types, they just have to use the complex
> scheme as mentioned on the page I'm mentioning above.
>

Yeah, the important thing is to not lose the cycleway=opposite_lane value.

>> bicycle:oneway=no, oneway:bicycle=no, bicycle_oneway=no...
>
> I'm not sure, I always get the feeling when I see those that it opens a
> whole new can of ambiguity problems, something I'm trying to fix
> here :-)

For the simple cases it seems to me that the only thing we're missing
is the ability to apply things like oneway and max_speed to specific
vehicle types. The max_speed:hgv style tags solve this.

It's obviously not enough to cope with max speeds for different weight
vehicles or with time restrictions etc., but I'm not convinced its
ambiguous at all.

Dave