[OSM-talk] turn restriction relations: via
gregory.williams at purplegeodesoftware.co.uk
Tue Mar 31 10:53:31 BST 2009
> -----Original Message-----
> From: talk-bounces at openstreetmap.org [mailto:talk-
> bounces at openstreetmap.org] On Behalf Of Shaun McDonald
> Sent: 31 March 2009 10:39
> To: Ed Loach
> Cc: talk at openstreetmap.org
> Subject: Re: [OSM-talk] turn restriction relations: via
> On 31 Mar 2009, at 10:05, Ed Loach wrote:
> > This talk of turn restriction relations reminds me of a junction
> > where I think I need to add loads of relations, but to date haven't
> > as many of them will include a roundabout as the from or to part.
> > http://is.gd/pOrJ (shortened permalink)
> > As you can see there is a roundabout, but there is also a dual
> > carriageway through the middle with the flow controlled by traffic
> > lights. If you are in the lanes which go through as the dual
> > carriageway you can't turn onto the roundabout, and if you are in
> > the lanes that lead onto the roundabout you can't turn onto the dual
> > carriageway lanes. I think for the relations to work I might have to
> > split the roundabout from a closed way into a number of sections,
> > but I've always drawn roundabouts as closed ways before. Will
> > splitting it cause issues with anything else? Although I might not
> > have to split as the via (node) will indicate where the restriction
> > actually applies, even when the dual carriageway lane crosses the
> > roundabout at two nodes. Or perhaps I could just split the dual
> > carriageway lanes somewhere in the middle of the roundabout to make
> > things easier for me to work out what restrictions I need to add.
> I have seen some people splitting roundabouts so that the bridge can
> be shown properly.
Also, there's a roundabout that's split into three separate ways in
Canterbury, because it's actually a different road name for each of
those ways. I've also seen several examples of roundabouts being split
to accommodate bridges, particularly at motorway junctions.
> > Comments welcome. I'm undecided between only_straight_on and
> > no_left_turn on the dual carriageway segments where they cross the
> > roundabout (and on the roundabout where it crosses the dual
> > carriageway). I think perhaps the first. Which I think means I need
> > to add 8 relations to the junction.
> I think the only straight on restriction might be a better option.
> > Ed
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