[Talk-GB] Where does a motorway start?

[Jez Nicholson]

I don't think you should be too harsh to the editor,
https://assets.publishing.service.gov.uk/media/58170307ed915d61c5000000/the-highway-code-traffic-signs.pdf#page=7
states that the chopsticks sign is the 'Start of motorway and point from
which motorway regulations apply'. I also take Andy's point that there are
physical limits to where they can be sited, leading them to be further
round the curve of the motorway link.

On Wed, Aug 3, 2022 at 9:51 AM Paul Norman via Talk-GB <
talk-gb at openstreetmap.org> wrote:

> On 2022-08-03 1:18 a.m., Andy Townsend wrote:
> > Hello,
> >
> > The DWG has recently had an email from someone asking about some
> > recent motorway edits.  These have been in various places, so I'll
> > pick an example local to me, where the A64 joins the A1(M):
> > https://nrenner.github.io/achavi/?changeset=123673170 .
> >
> > The edit moved the start of the motorway from where the roads diverge:
> >
> >
> https://www.mapillary.com/app/?focus=photo&pKey=2478290038984023&lat=53.856169399972&lng=-1.3365381&z=17&x=0.48881009070232434&y=0.6403049169362514&zoom=3
> >
> >
> > to just after the “chopsticks” sign visible in front of the lamppost
> > at the right of the carriageway in edit mode at
> > https://www.openstreetmap.org/#map=18/53.85550/-1.33895 :
> >
> >
> https://www.mapillary.com/app/?focus=photo&pKey=493444768591097&lat=53.855654360067&lng=-1.3384409007607&z=17
> >
> >
> > I suspect that this is more a question of style than anything else -
> > no router is going to send non-motorway traffic down a oneway section
> > of trunk link which only exits to a motorway link. Personally, I'd say
> > that the motorway starts where the roads diverge, but I didn't feel
> > strongly enough to comment about it when I saw another of these
> > changes a few days ago.  I said to the DWG's correspondent that I'd
> > ask here, so here this message is.
>
> I would say this is fairly clear. There is a link road between a trunk
> and a motorway, and it should be tagged as a motorway_link. In some
> cases it can be difficult to say what a link is, but it's clear in this
> case.
>
> For routing, as you've said, it doesn't really matter much. Because
> there's no other roads connected where the two link sections join, they
> can be combined into one (along with the ones closer to the motorway)
> and the only difference is going to be a tiny cost difference. If you
> were trying to route to or from a point on the section in question with
> a mode of transport that is allowed on trunk_link but not motorway_link,
> it could matter, but in practice the access restrictions are the same
> for the entire link.
>
>
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