[OSM-talk] Turn restriction docs

[Nic Roets]

On Sat, Nov 29, 2008 at 8:31 PM, Erik Johansson <erjohan at gmail.com> wrote:

>
> Ok.. so do you use two via nodes to resolve the left/right turn  issue
> with out using lat/lon?
>

No. gosmore expects exactly one 'via' object and it must be a node. So
complicated (multistate) restrictions aren't supported (yet) e.g. specifying
no U-turn at traffic_signals where another road cross.

At T junctions the ambiguity is resolved using
restriction=no_left_turn/no_right_turn. Where slipways join bidirectional
roads (at high speed), the ambiguity is resolved with restriction=no_u_turn
(only_straight_on ).

At 4 way junctions you should one of the ways (making 2 Ts).

Some people want us to split ways whenever an ambiguity arises, but it will
mean we have to split a number of major roads at every little intersection
where a service road joins.

So a better solution would be to resolve the ambiguities with tags like
from/to_direction=forwards/backwards (unimplemented). Routing engines
already need to know about forwards / backwards. And it will be a lot easier
to write a user friendly visual editor for turn restrictions.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20081129/5ecec167/attachment.html>