[OSM-talk] Complex turn restrictions

[Shaun McDonald]

On 24 Apr 2009, at 15:01, Dirk-Lüder Kreie wrote:

> Aun Johnsen (via Webmail) schrieb:
>> On Thu, 23 Apr 2009 22:19:39 -0700, Paul Johnson  
>> <baloo at ursamundi.org>
>> wrote:
>
>> http://maps.google.com/?ie=UTF8&ll=44.92934,-123.02527&spn=0.000872,0.002414&t=k&z=19
>>> For those who aren't familiar with why this is a hard question:
>>>
>> This is not a turn restriction, as you are allowed to turn left  
>> from the
>> road, but rather a lane change restriction. This must be handled in  
>> the map
>> somehow as well, but there is no way to tag it at the moment to my
>> knowledge. I suggest somebody start working on a lane relation, as  
>> much
>> information lies in lanes, such as specified lanes for left and  
>> right turn,
>> off-ramps, where you can change lane, where you cannot change lane,
>> differented restrictions in different lanes (such as you cannot  
>> change
>> between the left-most lanes where an onramp comes on right-hand  
>> side of a
>> motorway, restrictions applying only for one movement, not the  
>> other (i.e.
>> you can change lane to the left, but not to the right). I am more  
>> than
>> willing to help you form such a relation, but doesn't have time to  
>> do the
>> work myself.
>
> I tend to create a way per lane if the lanes are separated by legal or
> physical means that prohibit lane change.
> so this intersection would encompass some oneway segments that will  
> not
> allow any router to send people coming from the north (22, 99?) to  
> turn
> left onto the 17th St SE.

I would agree, that it would be far simpler to split this road into  
several parallel ways, with a way for the cyclist at an appropriate  
point. It may be worth adding a note=There are parallel ways here due  
to lane movement restrictions. To prevent someone merging the ways to  
what they think is correct.

Shaun