Odd dual carriageway

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Owain
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Re: Odd dual carriageway

Post by Owain »

jervi wrote: Wed Sep 18, 2019 14:53
Micro The Maniac wrote: Wed Sep 18, 2019 13:20
Chris5156 wrote: Thu Sep 12, 2019 21:08 That's D1, not D2!
As a total tangent, what is the Sabristi-speak for a D2 that has been hatched down to oblivion? D1 seems inadequate...
Road as described like this one https://www.google.co.uk/maps/@50.86459 ... 312!8i6656
I'd just say D1.
While the road surface may be wide, the actual driveable space is still restricted to one vehicle, although often I don't see overtaking restrictions (either signed or solid white lines) on these types of road, so I wouldn't call it an D1.5
Sure you could call them WD1 though.
I guess this is a grey area!

The examples given in this thread (whereby each carriageway is only wide enough for one vehicle to drive along it at a time) are obviously D1. However, where the outer lane has been hatched to discourage overtaking, but where the carriageway is still wide enough to overtake and there is no actual restriction in place to prevent overtaking (for example) I think we're probably still talking about a D2.

And, of course, there are also many examples of old stretches of D2 where one side has been hatched out (and restrictions against overtaking imposed) while the other side still allows overtaking. See here. Would that be a D2+1?

And what about this example: at one end it is indisputably D2, but at the other end it has been whittled down to a D1. It's all the same piece of road, and I'm not sure the width of the original carriageways (which were once D2 throughout) has ever been changed.
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Johnathan404
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Re: Odd dual carriageway

Post by Johnathan404 »

The D1/S2 abbreviations are an easy way to describe some common scenarios.

Inevitably SABRE will want to complicate things so that it precisely describes every possible set-up, in doing so losing all the simplicity and creating a complex new code with its own large manual.

Alternatively we can stick to using words when we need to describe something that's too complicated for a two-digit abbreviation! :D
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Re: Odd dual carriageway

Post by jervi »

Had a thought just now, was gonna start a new thread but this thread's name already suits it.
Are there any examples (preferably in the UK) of a dual carriageway, which has a permanent contraflow lane on one of the carriageways? In other words, carriageway A has two lanes northbound, and carriageway B has 1 lane southbound and 1 lane northbound. Or similar.
The closest I can think of is the perminater road at Heathrow, however that is more of two S2 running next to each other (but maybe many years ago it as a D2)
https://www.google.co.uk/maps/@51.47894 ... 312!8i6656
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Re: Odd dual carriageway

Post by Johnathan404 »

jervi wrote: Sun Sep 22, 2019 22:38 Had a thought just now, was gonna start a new thread but this thread's name already suits it.
Are there any examples (preferably in the UK) of a dual carriageway, which has a permanent contraflow lane on one of the carriageways? In other words, carriageway A has two lanes northbound, and carriageway B has 1 lane southbound and 1 lane northbound. Or similar.
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Re: Odd dual carriageway

Post by NottsLad »

Is the NSL on such rural D1s 70mph?
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Re: Odd dual carriageway

Post by Big L »

NottsLad wrote: Mon Sep 30, 2019 12:29 Is the NSL on such rural D1s 70mph?
Yes, and where sensible and possible I try to get to it.
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Re: Odd dual carriageway

Post by Moore_O »

Chris5156 wrote: Thu Sep 12, 2019 21:08 That's D1, not D2!

Yes, there's a few - one in Kent and a more famous one in Wales. I think we've had threads about them before, but "S1" is too short a search term for the forum software!
The 'more famous one' is in Kent, I think you'll find! :wink:

Assume you're thinking of the short section of the Pilgrim's Way near Aylesford - who can forget that bit of the Canterbury Tales where the Wife of Bath and the Shipman have a furious argument about what the speed limit is.

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Re: Odd dual carriageway

Post by Steven »

NottsLad wrote: Mon Sep 30, 2019 12:29 Is the NSL on such rural D1s 70mph?
It's also 70mph on single carriageway motorways.
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Re: Odd dual carriageway

Post by M4Simon »

Johnathan404 wrote: Sun Sep 22, 2019 22:35 The D1/S2 abbreviations are an easy way to describe some common scenarios.

Inevitably SABRE will want to complicate things so that it precisely describes every possible set-up, in doing so losing all the simplicity and creating a complex new code with its own large manual.

Alternatively we can stick to using words when we need to describe something that's too complicated for a two-digit abbreviation! :D
I believe that 'single lane dualling' is used in DMRB but I only recall seeing it in the context of a junction layout.

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Re: Odd dual carriageway

Post by Bryn666 »

Surely the winner is the access road to Sellafield. That's a weird as heck dual carriageway.
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Re: Odd dual carriageway

Post by jackal »

jervi wrote: Fri Sep 13, 2019 04:28 Just read the TSM, i'm not far wrong.
Chapter 4 - 5.3.2
Further advance warning up to a distance of two miles may also be given by a sign to
diagram 818.1. This sign may be used to encourage drivers to delay overtaking until the dual
carriageway is reached. Distances greater than two miles are not permitted, as this might result
in impatient drivers trying to overtake on an unsuitable length of road.
So either TSM is indulging the schoolboy error of thinking DC=overtaking opportunity, or it's making the error itself!
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Re: Odd dual carriageway

Post by jervi »

jackal wrote: Wed Oct 02, 2019 12:14
jervi wrote: Fri Sep 13, 2019 04:28 Just read the TSM, i'm not far wrong.
Chapter 4 - 5.3.2
Further advance warning up to a distance of two miles may also be given by a sign to
diagram 818.1. This sign may be used to encourage drivers to delay overtaking until the dual
carriageway is reached. Distances greater than two miles are not permitted, as this might result
in impatient drivers trying to overtake on an unsuitable length of road.
So either TSM is indulging the schoolboy error of thinking DC=overtaking opportunity, or it's making the error itself!
Well whoever wrote the TSM knows that DC doesn't necessarily mean two (or more) lanes, but I would agree that it reinforces the common misunderstanding of Dual Carriageway = 2 lanes in the same direction. Either Way the Dual Carriageway Ahead Sign isn't really fit for purpose in my opinion, but I TBH I can't think of a better alternative to it.
The most simple worded alternative would be "Overtaking opportunity ahead" OR "Overtaking opportunity 2 miles ahead", but this would have a few negatives, if 1.5miles ahead there a straight bit of S2 and drivers would use that opportunity to overtake, instead of a 2 lane Dual Carriageway half a mile beyond that. Also it could make drivers think they need to overtake, or reinforces the driving culture that overtaking is normal and encouraged, even if not needed. One positive is that it could be used on single and dual carriageways.

So in my view, the best way forward is to keep using the "dual carriageway ahead" sign where there is a D2 (or larger) with a speed limit of 50MPH and over with appropriate length for the majority of vehicles to overtake (400m+). Or in other words, where there is a genuine place to overtake due to the road becoming a DC, not just because the road is being a DC.

Also the creation of a new sign for SC with a dedicated overtaking lane. This would be the "Climbing Lane ahead" / "Climbing Lane x mile/yds ahead" signs, even though it may technically not be a "climbing lane", keeping it to those two signs would be simpler than all sorts of worded signs. Using a sign like "Overtaking Lane ahead" may again cause people to overtake unnecessarily, making it more dangerous for everyone.
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Re: Odd dual carriageway

Post by PhilC »

There's an unusual stretch of dual carriageway past Warwick University in Coventry.

https://goo.gl/maps/ksBcovjyKsFsF3zL8

There are also several unusual stretches along Broad Street, Birmingham. The central reservation is barely an inch above the level of the road surface and there are no keep left signs.

https://goo.gl/maps/xPJnxn4WkPxLawQr8
https://goo.gl/maps/c3f1uzsi8VDbiHr68
https://goo.gl/maps/6xY3qoGCqS78iftN8
https://goo.gl/maps/doo1bzMpDhG9KjNR6

Some of the central reservation has been removed recently and replaced with a painted hatched area.

https://goo.gl/maps/MJdHjrZFbT1Dw7Kq7
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Re: Odd dual carriageway

Post by jervi »

PhilC wrote: Fri Oct 04, 2019 00:38 There's an unusual stretch of dual carriageway past Warwick University in Coventry.

https://goo.gl/maps/ksBcovjyKsFsF3zL8

There are also several unusual stretches along Broad Street, Birmingham. The central reservation is barely an inch above the level of the road surface and there are no keep left signs.

https://goo.gl/maps/xPJnxn4WkPxLawQr8
I wouldn't really call that a dual carriageway. Even the first example you gave has a "two-way traffic" sign.
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Re: Odd dual carriageway

Post by belgarion »

This always amuses me, you get 2 lanes in each direction but not for long and they are not along side each other, don't know if there was a different layout previously.
Also pretty pointless as the whole lot lies right at the start of an average speed camera zone, so the cameras are there to catch you speeding, and its 50mph rather than national speed limit.

https://www.google.co.uk/maps/@53.42585 ... a=!3m1!1e3

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Re: Odd dual carriageway

Post by Robert Kilcoyne »

Yardley Wood Road in the Wake Green area of south Birmingham; the road has a section of D2/D1 here yet the dual carriageway does not extend either to the junction with the B4217 Wake Green Road to the north or to the B4146 Swanshurst Lane to the south:-

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Re: Odd dual carriageway

Post by Chris Bertram »

Robert Kilcoyne wrote: Fri Oct 04, 2019 13:51 Yardley Wood Road in the Wake Green area of south Birmingham; the road has a section of D2/D1 here yet the dual carriageway does not extend either to the junction with the B4217 Wake Green Road to the north or to the B4146 Swanshurst Lane to the south:-

https://www.google.co.uk/maps/@52.43869 ... 6656?hl=en
The formation for Yardley Wood Road south of Wake Green Road as far as the Yardley Wood roundabout is almost all wide enough to accommodate full dualling. Some of it has a service road in place, other parts just a wide grass verge; the main road is normally offset to one side. The section you mention functions more as an island for the junction with St Agnes Rd, with turning points near either end.
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Re: Odd dual carriageway

Post by jervi »

belgarion wrote: Fri Oct 04, 2019 13:30 This always amuses me, you get 2 lanes in each direction but not for long and they are not along side each other, don't know if there was a different layout previously.
Also pretty pointless as the whole lot lies right at the start of an average speed camera zone, so the cameras are there to catch you speeding, and its 50mph rather than national speed limit.

https://www.google.co.uk/maps/@53.42585 ... a=!3m1!1e3

Vince
That looks horrid, I'd guess it was a short stretch of D2/S4 (but longer than it currently is), however due to the bend at the bridge it was probably shortened to just the S4 part of it. If I was the local council I'd just make it S2 and change the lay-bys into a protected lay-by using the existing road space.

Few other ideas why it could be like that:
1. Maybe there were bus stops before the lay-bys were created, so they made the road extra wide to allow traffic to pass. Although there would be little reason to have a bus stop there.
2. Maybe it was extra roadspace after the bridge was built (if they built it beside the old bridge) and just decided to use that space as a S4.
3. It was expected for that corridor to become a dual carriageway, so when the bridge was built (/widened) only that short section to the east was upgraded in preparation of tying a D2 into the bridge in the future.
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Re: Odd dual carriageway

Post by marconaf »

Norfolktolancashire wrote: Thu Sep 12, 2019 20:53 On my latest sortie into Norfolk I was driving along a rural side road in the middle of nowhere near Wroxham when I came across a "Dual Carriageway Ahead" sign. Thinking it was a mistake I was surprised to find a sort of D2 separated by trees.

Are there other examples of these types of D2 on minor rural roads?

https://www.google.co.uk/maps/@52.75497 ... 312!8i6656
Fascinating example, I spent a couple of years recently in Norfolk and drove all over, the roads are random in that literally in the middle of nowhere with nothing at either end, you get a really decent stretch of straight, wide and even wider verges (places you could put the A1 through between the hedges! After a couple of miles reverts to narrow and twisty.

Having discussed it with colleagues I was told it was often a legacy of WW2 when Norfolk was an armed camp, not just the airfields but all the Army and both their mass of supporting infrastructure (fuel dumps, vehicle parks, accommodation, HQs, ammo dumps and so on and so on). Often roads and choke points were improved just in their local area to deal with congestion and the movement of outsize loads (stuff assembled locally at one depot and then moved to an airfield for instance).

In your case I note the field to the South at the Eastern end is left alone and has a large dark rectangle in it (concrete or asphalt pad under weeds?), with cross overs in the DC aligned with each end of that and a wide entrance with concrete looking bollards set well apart for a gate perhaps. I suspect some kind of WW2 depot with lots of vehicle moves and thus an emergency build of this lane just to help deconflict them in the vicinity. Be interesting to know the truth!

I’ve always been interested in the same stuff - Burnham Beeches near Slough is a lovely forested area now all closed off to vehicles, but criss-crossed with roads and verges/hardstanding - as the signs there say it was a vehicle (marinisation) preparation depot for dday and more.
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Re: Odd dual carriageway

Post by Robert Kilcoyne »

D1 on Moor Lane in Witton, Birmingham; the two carriageways are separated by columns supporting the M6 running directly above Moor Lane at this point:-
https://www.google.co.uk/maps/@52.52122 ... 6656?hl=en
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