[Tagging] Dispute prevention: meaning of lanes tag

Martin Vonwald imagic.osm at gmail.com
Mon Apr 23 09:35:57 BST 2012

Very good thoughts and examples - thanks for that.

I fully support you, that the lanes tag should not be another
estimation of width. I also agree, that we should not tag lanes, when
they are not obvious in some way.

Regarding the example with the parked cars: I think this case should
be handled by the parking-tags. If we start to reason "ok, there are
two lanes, but as cars are parking here, I dont tag this" it's getting
more complicated than necessary. I always recommend "clean" tags:
"lanes" count the lanes. End of story. Otherwise we put more meaning
in the value as there should be and just like it is right now with
lanes=1.5 (-> "there are two lanes, but they are narrow so I don't tag

Regarding width:lanes=2.0|2.0 . I don't agree. If the width is
evenly(!) distributed over the existing lanes, don't use the lanes
suffix, simply tag: lanes=2 and width=4. But if the width is NOT
evenly distributed, one has to use the lanes suffix, so
width:lanes=2.0|2.75 should never-ever be tagged (only) as width=4.75.

One last question: what would you recommend for estimations of the
width? width=x together with source:width=estimated or only est_width?


2012/4/22 martinq <osm-martinq at fantasymail.de>:
>> I've had a look for uk guidance as the uk's ordnance survey was
>> mentioned, and a lot of older uk advice appears based around a now
>> historic view that 'cars = saloon cars' and were 1.8m or less. If cars
>> were assumed to be 1.8m wide then implied OS figure of 4m for two lanes
>> makes sense.
> I am not sure we should base the lanes tag value on typical car width.
> IMO the lanes tag should *not* be another kind of estimate for the width.
> A further problem is the definition: For example the "euro track" has a
> maximum allowed width of 2.55m without mirrors (refrigerated ones even
> 2.60m). This would be as fair as basis as a "average" car in UK or a UK
> guide. And in US or India we may find another situation again.
> My opinion:
> If the width of the road can be estimated and no lanes are marked: We should
> tag the width (of the carriageway(*)) only (or est_width or
> width+source:width) and no lanes tag.
> (*) Sadly the width itself is pretty ambiguous tag at the moment (e.g. is it
> the width of the complete street or just the carriageway, etc.). But this is
> a topic for its own.
> When you look at following example:
> http://wiki.openstreetmap.org/wiki/File:Bangalore_India_traffic.jpg
> then I conclude: If there are no marked lanes, it lanes gets simply too
> subjective.
> My current practice:
> On non-residential areas (tertiary, etc.) I typically tag lanes=2 only if
> the road allows *two* trucks (that don't require police escort because they
> are wider than allowed, means >2.6m) to pass. In my area this means >5.2m.
> In residential areas/streets I omit lanes if they are not marked. Parking
> allowance and parking cars on the street/carriageway make the situation very
> complicated. Look here:
> http://bit.ly/I2hna7
> While the carriageway in this example is more than 6m wide and allows two
> trucks to pass, you also see parking cars in this street (I don't know the
> German law, but they might be allowed to do that). What would you do now?
> And if the parking allowance is time limited? For me lanes is simply not
> applicable here.
> --> I would tag the parking information with parking:lane, width, but not
> lanes.
> What I also propose: If lanes are marked, but narrow for trucks (e.g. just
> 2m each), I would tag them width:lanes=2.0|2.0 now. If there is a dedicated
> maximum width road sign --> maxwidth.
>> Though I'd think a road 4.3m wide would
>> fall under the 'lanes=1.5' idea
> [...]
>> After reading through these emails I'm beginning to think the
>> lanes=1.5 would less confusing for narrow two lane roads.
> -1
> 1.5 makes no sense. If we can agree that a lane is a "strip, which is wide
> enough for one moving line of motor vehicles other than motor cycles" (from
> the Vienna Convention of Road Signs, used as basis for local law in many
> countries all over the world) -- then either one line of vehicles can move
> -- or two.
> --> For me this lanes=1.5 is a clear indication for an attempt to turn the
> lanes tag into a rough width-estimate. I think the width tag is the better
> tag for width-estimates.
> martinq
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