I can't comment whether this is "proper" usage or not, but I can illustrate how I've personally tagged lanes at freeway exits:
Take, for example, this freeway interchange close to where I grew up (note: left-hand drive): https://goo.gl/maps/5eF35SVed452 There's no lane markings to indicate direction itself, but there is a solid line starting a few hundred metres out and continuing just past the ramp, indicating no lane changes from lane 2 to lane 1 (where lane 1 is the left-most lane). There is, however, overhead signage for this particular interchange as follows: https://goo.gl/maps/ApFqTg7vRQT2 (1 km out) https://goo.gl/maps/FTtiG5UHaxx (500 m out) https://goo.gl/maps/VMw9Rcpsua62 (at the ramp) The sign 500 m out is the key one -- that's the one that has the turn lane information on this. As such, were I to add turn lane data in this area (I wouldn't, as I moved out of that city in 2010 and don't consider myself to have sufficient local knowledge there any more), I'd tag as follows: From 500 m out until the point where the ramp separates: turn:lanes=slight_left;through|none|none The section with the painted lane restriction: change:lanes=yes|not_left|yes Now, this is an urban setting and the overhead signage makes (to me, anyway!) the tagging rather unambiguous. In a rural setting however, all you're likely to get is this: https://goo.gl/maps/ajR1ccg6g252 (signage 1 km from ramp) https://goo.gl/maps/NLm9VMNskKK2 (signage at the ramp) https://goo.gl/maps/6aE1NbsuguG2 (overhead view of the ramp) There's no explicit lane markings here, but once again, there's a painted line indicating no lane changes from lane 2 to lane 1 around the vicinity of the ramp, which implies turn:lanes=slight_left;through|none (and of course, explicitly specifies change:lanes=yes|not_left), so even through turn:lanes are implicit on the ground, I'd explicitly tag it. I personally see this as unambiguous as per the urban example. Now, when it comes to the US example that Jack posted (http://mapillary.com/map/im/7igAGXSa6EsUYlTIujXchw), it seems like there's nothing explicit or implicit, either from painted markings (either arrows or lane change restrictions) or signage (I jumped on Streetview and the only other sign I noticed was an "exit in 0.5 mi" sign, similar in nature to my rural "exit in 1 km" sign). In this case, I would side with "through;slight_right" -- even though there's nothing explicitly or implicitly specifying as such, the reality on the ground appears that one can only exit from the right-most lane while continuing to continue through, and the remaining lanes are for through traffic only. I can, however, see the rationale behind tagging "none;slight_right", as well as tagging nothing at all, and as such, I think that this is an issue that we need to find consensus on. That said, I believe Paul is quite correct with his statement that machines "need to be told about these restrictions in order for them to be able to provide useful feedback from it" -- something that isn't explicitly present (or maybe not even implicitly so) but appears obvious to a human on the ground isn't necessary obvious to a machine. --K On 26 August 2016 at 08:37, Paul Johnson <ba...@ursamundi.org> wrote: > On Thu, Aug 25, 2016 at 11:06 PM, David Mease <meas...@gmail.com> wrote: >> >> Road markings are both beneficial and useful for navigation. Cities and >> governments have paid a lot of money installing them all over globe >> precisely for these reasons. OSM would be well served to include them >> exactly as is. I don't hear a lot of people complaining about how those >> arrows on the roads led them astray. > > > Arrows on the road, at least in North America, are typically only installed > to indicate relatively unusual lane restrictions, with the typical lane > restrictions assumed to be common knowledge. This is where this trips up > automation, as machines need to be told about these restrictions in order > for them to be able to provide useful feedback from it or lane guidance will > be a NP-complete thing for data consumers to deal with. I mean, I get it, > don't tag for the data consumer. But on the other hand, don't break the > data consumer with stupid tagging schemes, either. > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
