[talk-au] Mapping interchanges levels or turn restrictions

[Roy Rankin]

The example I gave was a simplification to demonstrate the issues. From 
Johns response I did realize I had gotten the directions which I assumed 
is why it did not make sense to him.  If you want to visualize the 
situation look at the link I supplied 
(http://www.openstreetmap.org/?lat=-33.82907&lon=151.21494&zoom=17&layers=0B00FTF 
) and consider east bound traffic on Falcon Street turning right to go 
south crossing the west bound way and onto the freeway, this was my 
simple example. It might be clearer if you are use to JOSM to look at it 
rather than the slippy map.

There is a third solution which I have seen. Typically the interchange 
ways cross 2 other ways. Normally I think of the via in a turn relation 
being a node. I am not sure the routers work this way, but if the right 
turn lane is a separate way with a common nodes with ways it crosses 
(but turns are not allowed).The right hand turn then becomes a separate 
way as the on-ramp.

An only_straight_on relation is used with
from east bound way (ending where right hand way takes off)
via right hand turn lane
to freeway on-ramp

The question is will this stop routers from allowing turns on common 
nodes between right hand turn way and other crossing ways.

An example of this can be found here 
http://www.openstreetmap.org/?lat=-33.73853&lon=150.91979&zoom=17&layers=0B00FTF

Roy Rankin

On 01/12/2010 04:12 PM, Roy Wallace wrote:
> On Tue, Jan 12, 2010 at 2:57 PM,<cam_daw at fastmail.fm>  wrote:
>>
>> Would anyone else like to comment?
>
> Yes, but as John asked can you point us to the example? Would make it
> easier to follow...
>
> As for "2>  The ways cross without a common node but are on different
> layers. (Although physically using the same pavement where they
> cross).".....
>
> This doesn't sound like a good idea. IMHO they should only be on
> different layers if one way physically crosses over/under the other
> (i.e. at different "altitudes").
>
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