[Tagging] Dispute prevention: meaning of lanes tag

Alan Mintz Alan_Mintz+OSM at Earthlink.Net
Thu Apr 19 20:33:00 BST 2012

At 2012-04-19 04:38, Martin Vonwald wrote:
>* PSV lanes SHOULD be included (also [2]). Example: lanes=3 and
>lanes:psv=1 means we have three lanes and one OF THEM is for PSV only.

Same goes for HOV (high-occupancy-vehicles) lanes, unless they are 
separately mapped (which is a better solution for routing, given their 
controlled access).

>* Turn lanes SHOULD be included (see [2] and [5]).
>* The lane count should change, as soon as a) new lane has reached its
>full width or b) a lane starts to disappear (usually a merge with
>another lane) (also [5]).

Technically, yes, but it doesn't seem practical in developed areas in the 
US, which typically change lane configurations at every major intersection 
and then change back again. A typical secondary artery might be 2 lanes in 
each direction with a raised center island, expanding to 2 lanes in one 
direction and, in the other direction, a left-turn "pocket" (in place of 
the center island), 2 straight-ahead lanes, and a right-turn "pocket" (in 
place of some land or sidewalk on the right side). While these additional 
lanes can be added individually or the way broken to tag them, I just don't 
see people doing this. It seems like routers could just as easily assume 
these types of configuration between various road classes, unless told 
otherwise. I would tag such a road as lanes=4 (lanes=5 if the center island 
is, instead, a center turn lane).

>   - Two-way roads with a specified lane count, but without a specified
>lanes:forward OR lanes:backward and a lane count, that is divisible by
>two, are assumed to have half of the lanes in each direction, e.g.
>lanes=4 means two lanes in each direction if not specified otherwise.
>I will add a recommendation for this situation, to add explicit

If an odd number, assume a center turn lane (e.g. lanes=5 means 2 forward, 
2 backward, 1 center).

+1 to the rest.

Alan Mintz <Alan_Mintz+OSM at Earthlink.net>

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