[OSM-talk] Complex turn restrictions

Paul Johnson baloo at ursamundi.org
Fri Apr 24 06:19:39 BST 2009


In Salem, Oregon, I have encountered a ramp that I can't quite seem to
make a restriction that JOSM thinks is valid, so I'm wondering what the
expected way to handle such a situation is.  The area in question is
visible at
http://www.openstreetmap.org/?lat=44.929397&lon=-123.024784&zoom=18&layers=B000FTF

Coming from the flyover ramp to Mission Street eastbound, as well as
from the Mission Street bike lane ramp where that lane rejoins the road,
drivers and cyclists alike are faced with a No Lane Change line that
prevents a legal movement to the left turn lanes onto 17th Street.
Effectively, this means that you may or may not be able to turn left at
17th depending on how you entered from the next intersections west.  You
can see the pavement markings as they are on the ground at
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:

1) JOSM doesn't seem to want to have more than one "via" or have a way
as a "via" in a restriction relation; I'm not sure if this is right or
wrong for JOSM to expect.  What's the live use on this?

2) Solid white lane lines mean you can't change lanes in this area
(exception being bicycles are allowed to enter or leave their restricted
lane over the solid line adjacent to the bicycle restricted lane).

3) Only one lane change is allowed per vehicle per 1000 feet.  Lane
changes are unrestricted between all lanes for 60 feet between the two
intersections, and traffic moves at expressway speeds (40-50MPH).

So how does one handle such awkward turn restrictions (other than
slaughtering the civil engineer who came up with such a bogus
interchange to begin with)?

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 260 bytes
Desc: OpenPGP digital signature
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20090423/c04654ee/attachment.pgp>


More information about the talk mailing list