[Tagging] no_u_turn restrictions for every entry/exit into a roundabout when the way is split because of physical separation?

Thu Apr 5 04:09:39 UTC 2018

Actually, it’s not just relatively harmless “noise”. Because such no_u_turn restrictions are indistinguishable from e.g. this one: https://www.openstreetmap.org/relation/8182004 (which I just created), that actually has a sign “on the ground”: https://www.google.com.au/maps/@-27.2141567,153.0014115,3a,75y,100.42h,82.68t/data=!3m6!1e1!3m4!1s-vnw60jwbq7XyR_-zZfreg!2e0!7i13312!8i6656 (excuse the streetview link, don’t have another photo of it right now, but I’m driving past it almost every day and am well aware of it).

From: Tod Fitch <tod at fitchdesign.com> 
Sent: Thursday, 5 April 2018 09:50
To: Tag discussion, strategy and related tools <tagging at openstreetmap.org>
Subject: Re: [Tagging] no_u_turn restrictions for every entry/exit into a roundabout when the way is split because of physical separation?

Seems like tagging “noise” to me. I’d expect a router to use the roundabout itself because exiting, making a U turn and then re-entering the roundabout will be longer and thus slower. Since the no U turn relations are there to make routing work and a reasonable router won’t need them, I’d say they are “noise”. If I were to go in to fix something on that intersection, I’d probably remove the no U turn restriction(s). But I don’t think I’d go out of my way to find them.

Cheers!

On Apr 4, 2018, at 4:36 PM, osm.tagging at thorsten.engler.id.au <mailto:osm.tagging at thorsten.engler.id.au>  wrote:

I’ve noticed that someone from the Microsoft Open Map team is very busy adding turn restrictions all over the place (  <https://www.openstreetmap.org/user/shawat94/> https://www.openstreetmap.org/user/shawat94/ ).

In my local neighbourhood, I noticed that he added no_u_turn restrictions to all the nodes where a road into in/out of a roundabout is splitting (because of physical separation). Which basically amounts to 4 no_u_turn restrictions for every single roundabout.

e.g. here:

 <https://www.openstreetmap.org/changeset/57747093> https://www.openstreetmap.org/changeset/57747093

 <https://www.openstreetmap.org/changeset/57674063> https://www.openstreetmap.org/changeset/57674063

There is no actual no_u_turn sign in any of these locations, it’s just (mostly) physically a bad idea to attempt a u-turn here.

Just a few weeks ago I discussed exactly this in #osm and the conclusion was that it was neither necessary nor desirable to do this.

I made a comment about that to the first of the two changesets linked above, but haven’t gotten a reply.

So, what is the general opinion about this here? Should these turn restrictions be created or not?

Cheers,

Thorsten

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