Re: [Talk-GB] Motorway junctions where the slow lane seperates from the through lanes

[Paul Jaggard]

Hi


I would suggest that the motorway should not be split until the point 
where the two halves physically diverge; instead, where there's a drop 
lane, use turn:lanes and destination:lanes tags to indicatethe presence 
of the drop lane.


My reasoning for this:

- firstly, there's no physical separation between the drop lane and the 
main line of the motorway, and it's still physically and legally 
possible to change between the two, and


- secondly, splitting a motorway based on different lanes having 
different destinations sets an awkward pattern, which taken to extremes 
means we end up splitting roads all over the place based on lane 
markings.  Sometimes that's necessary to make routing work sensibly 
through complex junctions, but I'd argue that this isn't one of those cases.



Best illustrated with examples:

Drop lane starts here.  Before this point, a single way with lanes=3.  
After this point, still a single way, with lanes=3, 
turn:lanes=slight_left|through|through :


https://www.mapillary.com/app/?pKey=v4H-uhxh9QQYjzL1b_BNMg=photo

The drop lane then runs for 300 metres, where there's no physical (or 
legal) barrier between the lanes, so still a single way with lanes=3, 
turn:lanes=slight_left|through|through :


https://www.mapillary.com/app/?pKey=S-dGYQdsR7olODRufbB5bg=photo

Then the actual split, where first there's a legal barrier (solid white 
paint), then a physical one (grass, barrier, trees, hillside, etc):


https://www.mapillary.com/app/?pKey=1WY5HbP5K-vpUnAT0voYGw=photo

It's here where I'd suggest we'd split into highway=motorway_link, 
lanes=1 (lanes=2 shortly thereafter), and highway=motorway, lanes=2, 
with a shortish Y-shaped transition to make it look sensible.  Of 
course, at this point the main line of the motorway loses the turn:lanes 
tag, and you can then add turn:lanes tags to the slip road as it widens 
out for the roundabout at the end.  The middle point of the Y (and not 
the start of the drop lane) carries the highway=motorway_junction and 
associated tags.


You could also add destination:lanes tags to label up the signed 
destinations, and destination:ref:lanes=A4174|M32|M32.



Incidentally, for me, /this/ is the sort of situation justifying 
separate, parallel ways on a motorway: 
https://www.mapillary.com/app/?pKey=AL0RC-DyWe27PMQEAS1uZA=photo



TL;DR?  Don't split based on lane markings, it's not a 300-metre-long 
physically separate way, it's just a lane with a different destination.  
Instead use turn:lanes, destination:lanes and destination:ref:lanes tags 
to indicate the drop lane.



Cheers,


Paul ("southglos")



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Re: [Talk-GB] Motorway junctions where the slow lane seperates from the through lanes

[Neil Matthews]

This is a changeset that is under discussion:
https://www.openstreetmap.org/changeset/79260663#map=16/51.5089/-2.5232

The disagreement is that there may be the start of an "exit lane", but
there is no physical separation where the junction has now been modified
-- see the changeset dicsussion for background info.

Local mappers would prefer that the junction were to be split where
there is a physical, rather than a logical separation,
https://wiki.openstreetmap.org/wiki/Editing_Standards_and_Conventions#Divided_highways

Cheers,
Neil


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Re: [Talk-GB] Motorway junctions where the slow lane seperates from the through lanes

[Mike Parfitt]

Have a look at www.openstreetmap.org/changeset/79582073

On my Samsung Tablet I have been using Bing satellite images with the Vespucci 
editor, but other images also show the road markings quite clearly.

From: Ed Loach 
Sent: 14 January 2020 13:45:34
To: 'Paul Berry' ; 'Mike Parfitt' 
Cc: talk-gb@openstreetmap.org 
Subject: RE: [Talk-GB] Motorway junctions where the slow lane seperates from 
the through lanes


See also

https://wiki.openstreetmap.org/wiki/Lanes

which has some quite good notes on how to map lanes. I suspect this is how 
OsmAnd knows to give me lane guidance (can’t think how else it could know).



I suspect based on that you’d want to begin your new way for the drop lane 
where the lane splits away from the main carriageway, with an earlier split for 
lanes=3, turn:lanes=slight_left|through|through with lanes=1 on the new way and 
lanes=2 on the main way after the split.



Ed



From: Paul Berry
Sent: 14 January 2020 13:15
To: Mike Parfitt 
Cc: talk-gb@openstreetmap.org
Subject: Re: [Talk-GB] Motorway junctions where the slow lane seperates from 
the through lanes



Hi Mike,



Interesting points and no easy answer I fear.



I think in mapping terms the midlines of each carriageway after the diverge 
will look more like a upside-down Y and I tend to do a bit of smoothing to make 
it look less abrupt. I think this is what you're getting at (apologies if not). 
It's not dissimilar to the situation where a single-carriageway road splits 
around an island: because the way is drawn as a line—not an area—the 
carriageway split is always going to look more dramatic drawn that way compared 
to the smooth continuous reality of what's on the ground.



In the situation of a lane drop don't forget to keep track of the lanes= 
in the keys.



It might be easier if you just go ahead and map as you see fit then post the 
changeset link if you want further commentary.



Regards,

Paul



On Tue, 14 Jan 2020 at 08:26, Mike Parfitt 
mailto:m_parf...@hotmail.com>> wrote:

The technical term is a drop lane.  This might later intersect with a 
roundabout, join with another motorway or primary road etc.  Between junctions, 
a single way for each direction is commonplace.  At junctions, there are ways 
for the through lanes and for traffic exiting and entering the motorway.

For example, on a 3-lane motorway with 3 lanes going in one direction and no 
junction anywhere near, the way would typically be placed along the centre of 
lane 2.

However, when lane 1 is designated as a drop lane, what was being mapped as 1 
way needs to split into 2 ways.

The question is where ?

There are various anticipatory changes in road markings well ahead of the 
physical separation of the asphalt, together with blue and white signs, some of 
which precede the first of the changes in road markings.

In the case described above, my convention is to pick the start of the shorter 
dashes between the drop lane (1) and the through lanes (2 and 3).  From then 
onwards, the way for the through lanes is mapped along the longer dashes 
dividing lanes 2 and 3, while the way for the drop lane is mapped along the 
centre of lane 1.

Others do it differently.

See "https://www.gov.uk/government/publications/traffic-signs-manual; from 
where you can download "Traffic signs manual chapter 5 road markings (2019)" 
which is a PDF.  Page 82 contains figure 7.7 and text documenting drop lane 
road markings.

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Re: [Talk-GB] Motorway junctions where the slow lane seperates from the through lanes

[Ed Loach]

See also 

https://wiki.openstreetmap.org/wiki/Lanes

which has some quite good notes on how to map lanes. I suspect this is how 
OsmAnd knows to give me lane guidance (can’t think how else it could know).

 

I suspect based on that you’d want to begin your new way for the drop lane 
where the lane splits away from the main carriageway, with an earlier split for 
lanes=3, turn:lanes=slight_left|through|through with lanes=1 on the new way and 
lanes=2 on the main way after the split.

 

Ed

 

From: Paul Berry 
Sent: 14 January 2020 13:15
To: Mike Parfitt 
Cc: talk-gb@openstreetmap.org
Subject: Re: [Talk-GB] Motorway junctions where the slow lane seperates from 
the through lanes

 

Hi Mike,

 

Interesting points and no easy answer I fear.

 

I think in mapping terms the midlines of each carriageway after the diverge 
will look more like a upside-down Y and I tend to do a bit of smoothing to make 
it look less abrupt. I think this is what you're getting at (apologies if not). 
It's not dissimilar to the situation where a single-carriageway road splits 
around an island: because the way is drawn as a line—not an area—the 
carriageway split is always going to look more dramatic drawn that way compared 
to the smooth continuous reality of what's on the ground.

 

In the situation of a lane drop don't forget to keep track of the lanes= 
in the keys.

 

It might be easier if you just go ahead and map as you see fit then post the 
changeset link if you want further commentary.

 

Regards,

Paul

 

On Tue, 14 Jan 2020 at 08:26, Mike Parfitt mailto:m_parf...@hotmail.com> > wrote:

The technical term is a drop lane.  This might later intersect with a 
roundabout, join with another motorway or primary road etc.  Between junctions, 
a single way for each direction is commonplace.  At junctions, there are ways 
for the through lanes and for traffic exiting and entering the motorway.

For example, on a 3-lane motorway with 3 lanes going in one direction and no 
junction anywhere near, the way would typically be placed along the centre of 
lane 2.

However, when lane 1 is designated as a drop lane, what was being mapped as 1 
way needs to split into 2 ways.

The question is where ?

There are various anticipatory changes in road markings well ahead of the 
physical separation of the asphalt, together with blue and white signs, some of 
which precede the first of the changes in road markings.

In the case described above, my convention is to pick the start of the shorter 
dashes between the drop lane (1) and the through lanes (2 and 3).  From then 
onwards, the way for the through lanes is mapped along the longer dashes 
dividing lanes 2 and 3, while the way for the drop lane is mapped along the 
centre of lane 1.

Others do it differently.

See "https://www.gov.uk/government/publications/traffic-signs-manual; from 
where you can download "Traffic signs manual chapter 5 road markings (2019)" 
which is a PDF.  Page 82 contains figure 7.7 and text documenting drop lane 
road markings. 

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Re: [Talk-GB] Motorway junctions where the slow lane seperates from the through lanes

[Paul Berry]

Hi Mike,

Interesting points and no easy answer I fear.

I think in mapping terms the midlines of each carriageway after the diverge
will look more like a upside-down Y and I tend to do a bit of smoothing to
make it look less abrupt. I think this is what you're getting at (apologies
if not). It's not dissimilar to the situation where a single-carriageway
road splits around an island: because the way is drawn as a line—not an
area—the carriageway split is always going to look more dramatic drawn that
way compared to the smooth continuous reality of what's on the ground.

In the situation of a lane drop don't forget to keep track of the
lanes= in the keys.

It might be easier if you just go ahead and map as you see fit then post
the changeset link if you want further commentary.

Regards,
*Paul*

On Tue, 14 Jan 2020 at 08:26, Mike Parfitt  wrote:

> The technical term is a drop lane.  This might later intersect with a
> roundabout, join with another motorway or primary road etc.  Between
> junctions, a single way for each direction is commonplace.  At junctions,
> there are ways for the through lanes and for traffic exiting and entering
> the motorway.
>
> For example, on a 3-lane motorway with 3 lanes going in one direction and
> no junction anywhere near, the way would typically be placed along the
> centre of lane 2.
>
> However, when lane 1 is designated as a drop lane, what was being mapped
> as 1 way needs to split into 2 ways.
>
> The question is where ?
>
> There are various anticipatory changes in road markings well ahead of the
> physical separation of the asphalt, together with blue and white signs,
> some of which precede the first of the changes in road markings.
>
> In the case described above, my convention is to pick the start of the
> shorter dashes between the drop lane (1) and the through lanes (2 and 3).
> From then onwards, the way for the through lanes is mapped along the longer
> dashes dividing lanes 2 and 3, while the way for the drop lane is mapped
> along the centre of lane 1.
>
> Others do it differently.
>
> See "https://www.gov.uk/government/publications/traffic-signs-manual;
> from where you can download "Traffic signs manual chapter 5 road markings
> (2019)" which is a PDF.  Page 82 contains figure 7.7 and text documenting
> drop lane road markings.
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[Talk-GB] Motorway junctions where the slow lane seperates from the through lanes

[Mike Parfitt]

The technical term is a drop lane.  This might later intersect with a 
roundabout, join with another motorway or primary road etc.  Between junctions, 
a single way for each direction is commonplace.  At junctions, there are ways 
for the through lanes and for traffic exiting and entering the motorway.

For example, on a 3-lane motorway with 3 lanes going in one direction and no 
junction anywhere near, the way would typically be placed along the centre of 
lane 2.

However, when lane 1 is designated as a drop lane, what was being mapped as 1 
way needs to split into 2 ways.

The question is where ?

There are various anticipatory changes in road markings well ahead of the 
physical separation of the asphalt, together with blue and white signs, some of 
which precede the first of the changes in road markings.

In the case described above, my convention is to pick the start of the shorter 
dashes between the drop lane (1) and the through lanes (2 and 3).  From then 
onwards, the way for the through lanes is mapped along the longer dashes 
dividing lanes 2 and 3, while the way for the drop lane is mapped along the 
centre of lane 1.

Others do it differently.

See "https://www.gov.uk/government/publications/traffic-signs-manual; from 
where you can download "Traffic signs manual chapter 5 road markings (2019)" 
which is a PDF.  Page 82 contains figure 7.7 and text documenting drop lane 
road markings.
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