[talk-au] How do I map left only turning lanes on a motorway?

cleary osm at 97k.com
Mon Jan 29 10:09:50 UTC 2018

I am no expert on mapping lanes and I defer to those with better
knowledge. However common sense suggests to me that vehicles are able to
move between lanes, whether into other lanes for vehicles travelling in
the same direction or overtaking in a lane normally used for traffic in
the oppisite direction.
However if it is not possible or permissible for traffic to move into a
nearby way, then I think it is a separate way, not a lane. I mapped one
location in suburban Sydney where the left lane was for traffic turning
left a couple of hundred metres further along, but traffic was not
permitted to change in that last 200 metres. The left lane traffic had
to turn left while other lanes could not move into the left lane or vice
versa. I think it correct to map a separate way for that 200m.
The most extreme example I know is on the Sydney Harbour Bridge where
the most eastern lanes are physically separated from other lanes for a
couple of kilometres and they are signposted with different names Cahill
Expressway and Bradfield Highway. They may be physically adjacent but
there is no crossover except one place for buses in the buses-only lane.
It would only confuse people if the two ways were merged and regarded as
lanes of the same way.
I don't know the road about which this discussion started but, if not
possible to change lanes, then I think it is correctly mapped as a
separate way. If it is possible to change lanes, then they would be
correctly mapped as lanes.
I would say that physical proximity is not the determining
characteristic. However I defer to those with better knowledge, if they
hold a different view.

On Mon, Jan 29, 2018, at 8:20 PM, Joel H. wrote:
> Hey everyone scrap that last message, I found out myself it has to be> turn:lanes=slight_left|left;through

> On 29/01/18 17:02, David Dean wrote:
>> Hi Joel, 
>> I believe that that example is not mapped correctly, as the turning
>> lane should only become a separate way when it reaches an actually,
>> physical separation. While it is just a turning lane, it should just
>> be indicated by lane tagging on the main way.>> 
>> I'd move the separation up to the physical separation, and map the
>> turning lane information on the main way.>> 
>> We have a few of those in the Brisbane area where intersections are
>> overly complicated because an early (no longer active) mapper
>> really liked mapping turning lanes as separate ways, and not all
>> have been fixed.>> 
>> - David
>> On Mon, 29 Jan 2018 at 16:59 Joel H. <95.5.radio at gmail.com> wrote:
>>> Hello, I'm adding lane data to the Inner City Bypass in Brisbane.
>>>  In this spot here: https://www.openstreetmap.org/way/23615424
>>>  there is 3>>>  lanes, however the left turn only lane is already mapped as a
>>>  separate>>>  motorway link. My intention is to add turning lane data to this
>>>  part of>>>  the ICB.
>>>  Should I map this third left lane on the ICB and move the
>>>  linking lane>>>  closer to the turn off. Or should these lanes be as separate
>>>  roads, as>>>  it is now with the linking lane having 1 lane and the ICB having 2.>>> 
>>>  _______________________________________________
>>>  Talk-au mailing list
>>> Talk-au at openstreetmap.org
>>> https://lists.openstreetmap.org/listinfo/talk-au
>> --
>> http://dbdean.com
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