On Wed, Apr 5, 2017 at 6:29 PM, Tom Pfeifer <[email protected]> wrote:
> On 06-Apr-17 04:09 AM, Kevin Kenny wrote: >> >>> Do we have a scheme for tagging such a beast? >>> >> > You can combine turn:lanes [1] with change:lanes [2], the first describe > which lane you have to use for which turn, the second where you can change > lanes and where not. > > [1] https://wiki.openstreetmap.org/wiki/Key:turn > [2] https://wiki.openstreetmap.org/wiki/Key:change > > If you want to show us the current situation, you can drive along with the > mapillary app and upload, so you don't need to show outdated G***** > pictures ;-) > Before doing the Mapillary thing, I have to rig a dashcam first, or at least have a passenger. The one series of Google pictures showing the signs was at least to explain the idea. The combination of turn:lanes and change:lanes sounds plausible, if it will actually work. I presume that the routing and navigation systems[1] have some presuppositions about lane continuity through an intersection? Let's say that I have a setup where A is the stem of a T intersection while B and C are its left- and right-hand branches. On A I have tagged: lanes=5 lanes:forward=3 lanes:backward=2 turn:lanes=right|through|left|left|right change:lanes=yes|yes|no|no|no I suppose, given the signage, I could add direction:lanes=||Union Street|Seward Place|Union Street to indicate what the overhead signs say. On B I have lanes=4 lanes:forward=2 lanes:backward=2 turn:lanes=right||through|through;left|right change:lanes=yes|right_only|no|no In short, I have two lanes turning left from the forward direction of A into the forward direction of B, and the two lanes of B go through;left and right respectively at the next intersection. Presumably, a routing and navigation system will expect that the leftmost lane of A will become the leftmost lane of B after the turn, while the center lane of A will become the right lane of B? That's the only way I can see this scheme working. It would involve some fairly tricky graph-tracing to deduce that a vehicle planning to turn right after B must be in the center lane approaching A, but I suppose that sort of thing is what routers are good at. Then a navigation system could announce, "Take the center lane and follow signs toward Seward Place". I'm guessing, considering the diversity of responses, that this functionality is slightly beyond what our actual navigation systems have to offer at present, but it at least gives me hope for a path forward. I may or may not trouble to tag these things, since I suspect they will change again before there's an actual data consumer for them. At least, I can see that it's possible. I had either missed 'change:lanes' altogether, or else had seen that it was languishing in 'Proposed' status and moved on. ---- [1] Yes, I understand the difference, but don't always spell out the whole phrase - when I said 'router' I really meant the whole stack.
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