[OSM-talk] [Talk-us] Am I mapping this wrong, or should the router be fixed for this?

Mike Thompson miketho16 at gmail.com
Mon Jul 27 17:10:40 UTC 2015

In reality there is only one set of stop lights there, correct? In other
words, if one were headed south on McKnight Road turning east on Seibert,
one would not have to stop (assuming red lights) three different times.

1) A routing engine should have some heuristics to interpret the three (in
this case) nodes tagged "highway=traffic_signals" as one.

2) There should be some cost in a routing engine for making a u-turn so as
to discourage such routes even if there was an extra set of signals. Making
a u-turn does take time (one can not go from the posted speed limit in one
direction to the posted speed limit in the other direction instantly). The
presence of other traffic in the opposing directly would add further to the
time needed to make a u-turn as one would have to wait for an opening.


On Mon, Jul 27, 2015 at 9:58 AM, James Mast <rickmastfan67 at hotmail.com>

> I've been normally mapping slip lanes as '_link' highways at intersections
> since the beginning.  However, as most fellow US mappers know, they almost
> never have 'speed limits' posted for them, and that seems to help cause
> problems in some routing programs when they give those slip lanes a speed
> limit higher than the main highway.
> Anyways, I've been using OSMAnd recently for occasional offline routing on
> my tablet and have come across weird routing (I'd like to call them 'bugs')
> at some intersections that have 3+ traffic lights nodes at them because of
> the roads being divided.  Here, OSMAnd routes me onto a slip lane, makes a
> U-Turn on the side road, and then continues the across the main road to
> accomplish what a simple 'left turn' could have done [1], all to avoid '1'
> traffic light node.  So, I go report the 'bug' on the OSMAnd Google group
> [2], and then somebody forwards it to the GitHub site [3].
> In the response I get back on GitHub, one of the maintainers of OSMAnd
> says it's a 'map data' issue and closes it.  Claims that in the 'maneuver',
> since it avoids an extra traffic light node, it's the shortest route, even
> though it does that funky U-Turn.  Say what?!  I mean, honestly, if both
> MapQuest Open & OSMR can do that left turn 'normally' without needing to
> make a funky U-Turn, something has to be wrong in OSMAnd, right??  Sure,
> there isn't a 'NO U-Turn' sign posted for this maneuver, but still, the
> routing engine shouldn't be suggesting it since there isn't a 'NO Left
> Turn' relation there preventing the left turn from McKnight SB to Siebert
> EB.
> So, that leads me to my question.  Does anybody think I've tagged the
> intersection incorrectly?  This is how I've been tagging intersections like
> this from since the start, and I know most other US mappers have been doing
> the same.  Or should I start adding 'false' U-Turn restrictions to prevent
> the routing bugs and then be called out as 'tagging for the router', or
> even maybe start putting traffic light nodes at the stop lines for
> intersections that have both roads divided (and just leave simple one-node
> intersections as-is)?
> I'm very curious to see what others have to say about this to see how I'll
> move forward when I map in the future.  Also, don't hesitate to respond at
> the Google Group post or the GitHub one too as I get the e-mail
> notifications from them as well.
> -James
> [1] - (MapQuest routing, OSMAnd suggestion in [2] link) -
> <https://www.openstreetmap.org/directions?engine=mapquest_car&route=40.53204%2C-80.01073%3B40.53002%2C-80.00614>
> https://www.openstreetmap.org/directions?engine=mapquest_car&route=40.53204%2C-80.01073%3B40.53002%2C-80.00614
> [2] - https://groups.google.com/forum/#!topic/osmand/XJ-HVOHhKEM
> [3] - https://github.com/osmandapp/Osmand/issues/1501
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