On Mon, Sep 19, 2011 at 7:33 PM, Stephen Hope <slh...@gmail.com> wrote: > On 20 September 2011 00:39, Gerhard Hermanns <herma...@ptt.uni-due.de> wrote: >> >> Traffic simulation (e.g. by cellular automata) is a use case for this. At >> crossroads it can make a huge difference for traffic engineering to know if >> a (turn) lane can contain 3 or 30 vehicles. >> To determine the "capacity" of a turn lane one would need information about >> its length - and one would get this easily if start and end point of the >> lane are known. Otherwise one would have to tag something like >> "turn_lane_left_1=xx" and "turn_lane_left_2=yy" (indicating length or >> capacity or whatever) in case of two turn lanes with different lengths. > > I'm not sure I would say "easily". What you're looking for here is > the number of cars that can be stored in the turning lane without > blocking flow in the through lanes, correct? Where do you mark the > extra lane width as starting? Where the lane first splits off? Where > the centre of the lane splits off? Where the lane is wide enough for > a car to fit? Where the line markings for a normal lane start? In > some places, these are all close enough that it wouldn't matter much > for your purposes, but there are places near me where these different > places would make a big difference in car count - 30 - 50m is not > unusual, and some are more. > > For a road splitting off from the main road, we would mark the split > in the centre of the road, so for consistency should lane count > changes be done the same way?
I'd say the lane count should be changed when the lane is completely there. So lanes=2 becomes lanes=3 when there are 3 full lanes. If you wanted you could even split off a way between lanes=2 and lanes=3 and call it lanes=2.5. Renderers could then interpolate in this zone. On Mon, Sep 19, 2011 at 3:45 PM, Nathan Edgars II <nerou...@gmail.com> wrote: > Ah, http://wiki.openstreetmap.org/wiki/Relations/Proposed/turn_lanes . Would > it be possible to modify this to allow a node for the beginning of the lane > rather than its length? If you split the way, to change the lanes=*, then you necessarily have a node at the beginning of the lane. And it's obvious what the node represents, rather than having to dig through relations to figure it out. A node in the middle of a way with no tags of its own, and no split in the way, is apt to get inadvertently moved or deleted. _______________________________________________ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
