[mkgmap-dev] question about ignored no_u_turn restriction

Tue Jul 28 16:38:34 BST 2015

Hi Gerd,

I guess I was a little to 'quick' with that example. ;-) Thanks for looking
into this.

Ben

On Tue, Jul 28, 2015 at 5:22 PM, Gerd Petermann <
gpetermann_muenchen at hotmail.com> wrote:

>  Hi Ben,
>
> okay, I did not yet think about the case that the device knows in which
> direction you are currently driving
> when it re-calculates a route. I did only consider the case that you are
> planning while standing still.
> If I remember correctly, this case will produce a message like "please
> make a u-turn",
> I never saw that it tells me to make a u-turn at a specific place.
>
> It's not easy to test if Garmin uses this restriction (when written by
> mkgmap), I have to think
> about it.
> @Steve: Do you see these restrictions in Garmin maps?
>
> Gerd
> PS: Your example is not good, as Quick Avenue is a (wrong) oneway, but
> that shouldn't matter here ;-)
>
> ------------------------------
> Date: Tue, 28 Jul 2015 16:50:30 +0200
>
> From: ben at bagu.org
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] question about ignored no_u_turn restriction
>
> Hi Gerd,
>
> In this example, if you're travelling southbound on North Harlem Avenue
> and you miss your right turn onto Quick Avenue, the GPS might suggest that
> you make a u-turn at the North Harlem Avenue / Ontario Street intersection
> so that you can double back get back to your original route. The traffic
> rule is saying that you're not allowed to make a u-turn at this
> intersection and the OSM data is capturing the traffic rule correctly.
>
> I've never been to this area so I can't actually test to see if the Garmin
> routing algorithm would try to do this u-turn. This is just an example that
> I'm using to try to figure if why the restriction is being ignored. I don't
> actually know the details Garmin routing algorithm but I have been routed
> on such u-turns in the past when I've missed a turn.
>
> Given that this is a legitimate type of 'no u-turn' restriction, if the
> Garmin map format or routing algorithm can't deal with it, there should be
> a message that says so in the warning. In this case, maybe an info message
> makes more sense - but you should probably decide how you want to present
> it since you wrote it. :-) The other side of this is that the Garmin map
> format or routing algorithm can actually handle this specific type of 'no
> u-turn' restriction, in which case it would be nice to have the restriction
> included in the maps.
>
> Thanks for your help and all your hard work on mkgmap!
>
> Ben
>
> On Tue, Jul 21, 2015 at 10:44 AM, Gerd Petermann <
> gpetermann_muenchen at hotmail.com> wrote:
>
> Hi Ben,
>
> unfortunately I did not add a comment to that part of the source which
> would explain
> why I coded it, but I think the reason is that the restriction has no
> effect on route calculation.
> I can't think of any case where the Garmin algo would route you along that
> u-turn.
> Do you have an example that proves this assumption to be wrong?
>
> If not, I can change the msg to say something like "has no effect", or
> please suggest a better text.
>
> Gerd
>
> ------------------------------
> Date: Mon, 6 Jul 2015 13:34:12 +0200
>
> From: ben at bagu.org
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] question about ignored no_u_turn restriction
>
> Just to follow up ... Does anybody know concretely that the Garmin format
> cannot handle and u-turn restriction with the same from and two way?
>
> Thanks, Ben
>
> On Sun, Jul 5, 2015 at 9:20 PM, Ben Konrath <ben at bagu.org> wrote:
>
> Hi Anor,
>
> Thanks for the tip but it seems that your suggestion breaks the OSM rule
> of manipulating the map for specific renderers (the renderer here being
> mkgmap). If the Garmin format truly doesn't support the u-turn restriction
> with the same to and from way at an intersection, we should come up with
> another solution.
>
> Ben
>
> On Sun, Jul 5, 2015 at 4:01 PM, A. Carlos <anorcarlos at hotmail.com> wrote:
>
>
>  Ben
>
> There I draw two routes, one in each direction, since there is a false
> median, then with 2-way, it's easy for a restriction
>
>
>
>
>
>
>
>
>
>
>
> *_______________________________________________________________________________________________________*
>
>  *Anor                                                              Co*
> *ncórdia SC *
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> ------------------------------
> Date: Sun, 5 Jul 2015 15:53:50 +0200
> From: ben at bagu.org
> To: mkgmap-dev at lists.mkgmap.org.uk
> Subject: Re: [mkgmap-dev] question about ignored no_u_turn restriction
>
>
> Hi Thorsten,
>
> Thanks for your reply. This type of restriction is probably a country
> specific thing. In Ontario Canada, you can make u-turns at intersections
> (regardless of the road is separation) if there is no sign indicating that
> you can't make the u-turn. Here's the information directly from the Ontario
> Ministry of Transportation:
>
> http://www.mto.gov.on.ca/english/dandv/driver/handbook/section2.6.11.shtml
>
> I realize that the link I sent previously is in the US but I suspect that
> it's the same policy there which is why the restriction is tagged like it
> is.
>
> Since the tagging seems to be valid, does the Garmin format support this
> type of restriction? If not then it's probably a good idea to indicate this
> in the warning message. Maybe the message should also be changed to an info
> message if there's no problem with the data. Does anybody have other
> insights?
>
> Thanks, Ben
>
> On Sun, Jul 5, 2015 at 2:47 PM, Thorsten Kukuk <kukuk at suse.de> wrote:
>
> On Sun, Jul 05, Ben Konrath wrote:
>
> > Does anybody know why this particular restriction is being ignored?
>
> Beside that this particular type of restrictions doesn't make
> any sense to me, I would guess the GARMIN format does not support it.
>
> If the to and from ways are the same, I have never seen a sign forbidding
> u-turns. Only, if you have two ways, structural seperated. But then I
> should tag the street that way and the restriction will not be ignored.
>
>   Thorsten
>
> --
> Thorsten Kukuk, Senior Architect SLES & Common Code Base
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nuernberg, Germany
> GF: Felix Imendörffer, Jane Smithard, Dilip Upmanyu, Graham Norton, HRB
> 21284 (AG Nürnberg)
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