[Tagging] lanes=x vs. xxx:lanes=a|b|c
imagic.osm at gmail.com
Mon Dec 15 13:04:37 UTC 2014
As I received a lot of questions lately, I want to point something out
relating to the values of the lanes key and the number of lane-dependent
values within any xxx:lanes key.
* The number of lane-dependent values within any xxx:lanes key is equal to
the number of lanes on the road, no matter if those lanes are full- or
half-width and no matter what kind of traffic they are designated to. 
* The value of the lanes key is equal to the number of full-width(!)
traffic lanes which are available to motorised(!) traffic. There are even
more exceptions - please see .
Therefore the value of the lanes key must be equal to or less than(!) the
number of values in any xxx:lanes key.
turn:lanes=through|through|right <- three values
bicycle:lanes=yes|designated|yes <- three values
This example is correct as there are only two lanes available for motorised
I want to make clear that I'm not happy with the definition of the lanes
key. But the definition is this way for ages and I definitively will not
try to change it (current usage: 4.5 mio times).
Therefore I would like to ask everyone not to ask me to change the JOSM
style  to show an error in the above example or any similar situation.
It is very hard to interpret access conditions within a style, so I can not
interpret all of them within a simple drawing style and therefore the style
only shows an error if the value of lanes is larger than the number of
P.S: If you want to change the definition of the lanes key and achieve
worldwide consensus, I will update the style within a minute.
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