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2 plus 1 road layout

Post by bprob
Since I had just posted about the N20, I figured I should start this thread to see if there is any consensus about mapping 2 plus 1 road layouts, before I started editing the 2 plus 1 section of the N20.
2+1 is not common in Ireland, (the attached link mentions 4 sites).
It is basically an otherwise normal stretch of road with a crash barrier down the middle. The number of lanes alternates every few kilometres in either direction to give opportunity for overtaking.
Most junctions are limited, (i.e. no right turn allowed), as the barrier carries on through the junction, but some have turning lanes provided.
It is NOT a dual carriageway. Houses still have (turn-restricted) access onto the road.
The link to the Cork Roads Office is here:
http://www.corkrdo.ie/2_plus_1_road_layout.php

I would be inclined NOT to separate the road into 2 lanes, one in either direction, because there is no margin between the lanes, but the difficulty with that is that the junctions would need extra careful attention, (and would have to be locked i would think, though there is no area manager for that section of road named in the cartouche).
However, some could justifiably argue for the section of road to be mapped as 2 separate roads as you can't navigate from one direction of travel onto the other like you could on a normal road.

Has anyone any opinions?
Or experience of the other 2+1 in ireland:
Co.Cork N20 Rathduff to Mallow Retrofit 9km
Co. Leitrim N1 Dromod Roosky Green field site 8km
Co. Monaghan N2 Clontibret to Castleblayney Green field site 15km
Co. Donegal N15 Ballyboffey Stronolar Green field site 16km

or abroad?
The link mentions it is used a lot in sweden
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Post by bprob
Thanks!
That is in line with my own thoughts on it, but wanted to double-check before making any changes to the road (the current mapping doesn't have most junctions linked, and seems to be double-mapped also - might need to go to support first to sort that out!)
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Post by bprob
fvwazing wrote:Support can hardly help you with that. Read the wiki on how to fix errors, connect junctions etc. by yourself.
From my original post:
the current mapping doesn't have most junctions linked, and seems to be double-mapped also - might need to go to support first to sort that out!)
.

Also is a topic currently being discussed elsewhere on the "Ireland" forum.

Thanks for the tip though: Really useful to read all available information before typing something foolish
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Post by bprob
llayden wrote:I'd agree with all the above! The road mentioned at Dromad is not a 2 plus 1. Its a 2 plus 2 with a wire & in places a crash barrier between the carriageways. There is only one road crossing and that is at a roundabout. It's in as a two directional road. I have changed some dual carriageways into two directional roads (in one case to have it changed back by an irate editor within 48 hours). For me the test is whether the GPS points show two distinct tracks. More irksome are the people who split roads coming into roundabouts to match the paint on the road!
The n20 is a wire barrier too but has 6 or 7 junctions.

It looks like there is a reasonable consensus on the matter of 2+1/2+2 roads.

the painted separation can be problematic alright. i find the bigger the roundabout, the more likely that a road forks at it, so the more likely it is that the gps points diverge too. I'd say the GPS should rule: if they diverge enough so that they look separate on the tracks, separate on the map?
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Post by davidg666
bprob wrote:Since I had just posted about the N20, I figured I should start this thread to see if there is any consensus about mapping 2 plus 1 road layouts, before I started editing the 2 plus 1 section of the N20.
[...]
I would be inclined NOT to separate the road into 2 lanes, one in either direction, because there is no margin between the lanes, but the difficulty with that is that the junctions would need extra careful attention, (and would have to be locked i would think, though there is no area manager for that section of road named in the cartouche).
My opinion: I agree with your inclination: definitely do not separate the road into two lanes, but have a single two-way road, and set turn restrictions accordingly. I don't see any need to lock road segments around junctions.

As others have remarked, such a road certainly wouldn't be wide enough for the GPS on a phone to be able to tell which side a user is on. In fact, I think we probably have a few dual carriageways in Ireland that need to be un-split - practice so far seems to have been to split all divided roads, even urban ones, no matter how wide or narrow the median.

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Post by dmcconachie
These should be done as a continuous single 2-way road. Even with 2 on each side the median is rarely wide enough to warrant splitting. Remember your mapping a satnav here, not some real life representation of the road system!

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Post by fvwazing
Support can hardly help you with that. Read the wiki on how to fix errors, connect junctions etc. by yourself.
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Post by fvwazing
Exactly so. If the GPSlayer, at the 200ft scale, shows clear white between the lanes - split. If not, dont. I found that by this rule I hardly leave any segments shorter than 10-12m in the map. Does not hurt a bit and the database with the Wazemap, the routing, the next editor of the area, the trafficdetection, the datatransmission to the clients: everything benefits.
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Post by llayden
I'd agree with all the above! The road mentioned at Dromad is not a 2 plus 1. Its a 2 plus 2 with a wire & in places a crash barrier between the carriageways. There is only one road crossing and that is at a roundabout. It's in as a two directional road. I have changed some dual carriageways into two directional roads (in one case to have it changed back by an irate editor within 48 hours). For me the test is whether the GPS points show two distinct tracks. More irksome are the people who split roads coming into roundabouts to match the paint on the road!
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