[OSM-talk] Turn left restriction on two way highways

[Alan Mintz]

At 2011-01-04 11:08, =?UTF-8?Q?M=E2=88=A1rtin_Koppenhoefer?= wrote:
>2010/12/30 Steve Bennett <stevagewp at gmail.com>:
> > On Thu, Dec 30, 2010 at 9:00 AM, Nic Roets <nroets at gmail.com> wrote:
> >> I know it may look like a lot of work adding all the no_left_turns, 
> but it's
> >> the right way.
> >
> > I have to disagree. OSM happens to have started in the UK, but that
> > doesn't mean that UK defaults make sense everywhere.
>
>
>I agree with Nic. AFAIK there are no defaults in OSM, not UK ones, and
>not others. Any not given Information is simply not yet entered.

There are defaults that are documented. Off the top of my head:

highway=*_link implies oneway=yes
junction=roundabout implies oneway=yes
no layer tag implies layer=0
no turn restriction at an intersection implies traffic can flow between the 
ways

Undocumented:
power=line implies layer=1 more than whatever it crosses (i.e. no crossing 
way error)


> > I think we definitely need to define defaults that make sense for each
> > country, and formalise this in some way. Preferably in the database,
> > perhaps as tags on the country boundary: "default:no_left_turn=yes" or
> > something.

Yes. Not just country, but at least one more level down.

--
Alan Mintz <Alan_Mintz+OSM at Earthlink.net>