[Tagging] Tagging u-turn restriction with continuous painted line

Philip Barnes phil at trigpoint.me.uk
Tue Jul 3 13:01:49 BST 2012


In France, a solid line means do not cross. It is more than do not overtake. On French motorways, the line between the main carriageway and the hard shoulder is broken for this reason.

In this case it does mean no U-turns, and a left turn restriction will fix the problem.

The router does need fixing however as U-turns around a roundabout divider island are rarely sensible and should not be treated as a junction.

Phil

--

Sent from my Nokia N9



On 03/07/2012 12:29 Janko Mihelić wrote:

I think "no_left_turn" is the best solution. The line on the middle of the street is not a u-turn indicator, it is an overtake indicator which can be tagged with overtaking=no and overtaking=both.

Are you sure that the dotted overtake line allows you to make a u-turn?

Janko


2012/7/3 Pieren <pieren3 at gmail.com>

Hi all,

Someone on the help site is questioning about a missing u-turn
restriction on a roundabout junction with splitter islands ([1] in
French). The problem is when you take one roundabout exit and want to
come back to the roundabout, a router like OSRM is telling you to
immediatly turn left after the divider although it is not allowed on
the ground.
He is pointing one example on OSRM :
http://map.project-osrm.org/?hl=fr&loc=47.291040,-2.356550&loc=47.291970,-2.356720&z=18&center=47.291347,-2.357208&df=0

With the aearial imagery (can be enabled on OSRM), we can see that the
u-turn is forbiden on about 10..15 meters after the splitter island
with a painted continuous line on the ground. I don't think a
no-turn-left-restriction relation is the best solution here since we
just indicate the restriction at the splitter island node but we don't
say at which point it will be possible to u-turn. I think the best
solution is to represent the continuous painted line on the 15 meters
road segment. The best tag I've found so far is the "divider" proposal
on the wiki ([2]) but is not very popular ([3]). Any thought ?

Pieren

[1] http://help.openstreetmap.org/questions/13939/interdiction-de-tourner-sur-entreesortie-de-rond-point
[2] http://wiki.openstreetmap.org/wiki/Proposed_features/Divided_road
[3] http://taginfo.openstreetmap.org/keys/divider

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