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

[Tod Fitch]

> On Jul 27, 2015, at 8:58 AM, James Mast <rickmastfan67 at hotmail.com> wrote:
> 
> 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

I use OSMand for a couple of reasons, but I am really beginning to think that the developers are confused with their routing logic and assumptions. I’ve largely fixed the routing via _link ways by changing routing.xml for my personal use. My changes delete all their odd penalty logic when changing from one class of highway to another and simply set a reasonable default assumed speed for ways without maxspeed tagging. Basically, I set the maxspeed assumptions to be that for my state and then set the _link speeds to 1/2 that of the associated highway class. That fix has been mentioned by several posters on the OSMand discussion area and has been routinely ignored over several OSMand releases.

So my opinion is that you are mapping correctly (as evidenced by other routing engines giving reasonable results) and that the OSMand team is getting confused about how to actually fix the routing issues that are routinely being posted on their Google Group area.

Cheers,
Tod
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