Road enthusiasts get a bit itchy about this. Two lanes each way - that's a dual carriageway, isn't it? To which the answer is: no, absolutely not.
Certainly lots of roads with two lanes each way are dual carriageways. And lots of dual carriageways have two lanes each way. But to be sure what constitutes a dual carriageway, we need to pick it apart a little bit. In a moment, we'll also take a short trip to Wales to see one of the UK's most bizarre dual carriageways, and perhaps see the true essence of dual carriagewayness.
Maybe the question we should start with is this one: what's a carriageway?
What's a carriageway?
Excellent question.
A carriageway is a paved surface for wheeled vehicles to travel on - literally, a way for carriages. A carriageway can be as wide or as narrow as necessary, and its width can be (but doesn't have to be) divided up by painted markings into multiple lanes. A lot of people think the "dual" in "dual carriageway" refers to two lanes side by side, but it doesn't.
So: a single carriageway road is a road made up of one paved surface. A dual carriageway road has two separate paved surfaces side-by-side, with some sort of physical divider or barrier between them.
What does it matter? Well, it becomes a bit more interesting when we look at a couple of examples. I promised you a trip to Wales a moment ago, and you will have one, but we're going to pop in to Birmingham first if that's OK. Let's go to Aston.
What's in Aston?
Why, the A38(M) Aston Expressway, of course.
The Aston Expressway is a tidal flow motorway, so it normally has three lanes each way, but electronic signals mounted over the road are used to operate four lanes one way and two the other during each rush hour. For that reason, it's a motorway without a central reservation.
The result is that the A38(M) has three lanes each way (or, sometimes, four one way and two the other), but it's still just a single carriageway road, because it has one unbroken paved surface.
Aston is home to the most extreme example of a single carriageway. To go the other way - and see a dual carriageway that looks nothing like a dual carriageway - we will make our long-awaited trip to Wales, and specifically to the village of Llywel.
Where?
Llywel. It's in the Brecon Beacons, lying just off the A40 between Sennybridge and Llandovery. It's at the foot of a steep hill, at the top of which is an expanse of moorland crossed by a military road that travels to the even more remote village of Tirabad.
The main thing in Llywel is a stone church. In fact, virtually the only thing in Llywel is a stone church, the rest of the village comprising two farms and about three houses.
Leading away from the church is a public road up the hill, which leads on to the military road, and - against all expectations - it's a dual carriageway.
The military road, built on relatively open moorland, is a conventional two-lane strip of tarmac, but the local road leading to it started life as a single-track country lane meandering its way between the fields. Whoever was given the job of widening it, presumably at the time the military road was built and in anticipation of it carrying lots of heavy army vehicles, decided not to make the existing road wider, but instead to put a new single-track lane alongside it. Perhaps that was thought easier, or perhaps it was done so that people wouldn't be tempted to try overtaking a platoon of slow army trucks grinding up the hill.
Whatever the reason, Llywel is home to the unusual spectacle of a single-lane dual carriageway stretching for over a mile up the hillside towards Tirabad.
It's indisputably a dual carriageway for three reasons.
- There are, physically, two road surfaces laid side by side with physical separation between them.
- There's a blue "keep left" sign at each end, which is the legal requirement for a dual carriageway to exist.
- The signs say "dual carriageway" on them in two languages.
Among other things, that means the speed limit on it is 70mph - as if such a thing were remotely possible here.
Let's take a short journey down the hill from the end of the military road back to Llywel.
At the top of the hill, the "keep left" sign marks the start of the dual carriageway.
The alignment of the road is basically that of a rural farm track, because that's what it is, complete with blind crests.
Field accesses and the occasional driveway are served by crossovers through the central reservation.
Occasionally the other half of the dual carriageway is visible ahead, like here.
It's going to keep dropping us off blind summits, isn't it?
Yes. Yes it is.
In the distance, across the valley, traffic is visible on the A40.
At the bottom of the hill, the church is suddenly in the way and the road swerves to the right.
With the churchyard on the left, we reach Llywel, and the end of the dual carriageway.
All of this is the long way round to make the point that a dual carriageway is all about physical road surfaces and not about the number of lanes, and it's not nearly as prescriptive a term as some people often think.
That is why engineers and people writing about roads in a professional capacity will use more specific language, like describing a "two-lane dual carriageway" or "dual three-lane carriageways". It's why roads like the A556 west of the M6, that have two lanes each way but no physical barrier down the middle, are subject to the single carriageway speed limit of 60mph and not the dual carriageway limit of 70.
And it's why, if you go to the Brecon Beacons, you should definitely make a trip to Llywel.
Comments
Sometimes even the highways department can't get it: A66 Bowes already is a dual carriageway.
https://www.google.com/maps/@54.5181524,-2.0161608,3a,20.6y,236.47h,85…
Not at this point it isn't
https://www.google.com/maps/@54.5181042,-2.0158013,3a,75y,273.65h,96.23…
That's very definitely a dual carriageway... the blog post above explains what the term means and it's not about having two lanes!
In Blackpool, Seasiders Way becomes D1 for all of a few hundred meters, probably to avoid the bridge pillars of Waterloo Road. It was built as access for Yeadon Way and has street lighting so would be 30mph.
Theres an interesting bit of dual carriageway on the A59 in Hutton near Preston. Its a dual carriageway with not only a footpath but also separate cycle lanes(these arent new, theyve been there since the road was made a dual carriageway). But it goes past a school, and there is a temporary 30MPH limit whilst pupils are leaving and arriving. Theres orange flashing lights as well so theres no excuse for speeding. And the speed limit for the whole stretch up to the roundabout at Hutton is 50MPH.
So is a central traffic island 3-4 metres long with keep left signs from both directions a very short dual carriageway, or not? Common sense would suggest not but it seems to satisfy the definitions of a physical barrier dividing two carriageways and correct signage, so if not, why not?
And what about a roundabout?
Surely in both cases its a moot point anyway...
The principle difference would be the speed limit and there's no way you could get up to 70mph and back down to 60mph again on a 4-metre stretch of tarmac reliably, nor would there be any point in doing so. The same applies to most roundabouts (though I grant there are a very few large enough where it might be possible, though again definitely ill-advised).
In any case, I would imagine that legally speaking there's some weasel-words in the legislation that says this is all considered in terms of the "principal character of a stretch of road" or some such, i.e. the road is still considered single or dual carriageway for its whole length, regardless of short commonplace interruptions for things like pedestrian crossing islands, unless there is signage to advise otherwise.
Surely a roundabout is a perpetual, single carriageway, one-way road?
I agree, but even then I feel like that's splitting hairs as almost any roundabout would be incredibly dangerous to travel around at either of 60 or 70 mph. That being said, I think a roundabout under motorway regulations would theoretically be legal to travel around at 70mph, if not signed with an alternative limit. Again, that's assuming it wouldn't be classed as illegal under "dangerous driving"!!
There's a tiny stretch around some trees on the edge of Salisbury.
https://www.google.co.uk/maps/place/Salisbury/@51.0612101,-1.8071377,19…
I have a hazy recollection about Dual Carriageway Signage. I recall from a good few years ago that to have a speed limit of 70 mph, a dual carriageway needed to have the Blue Dual Carriageway sign at the start otherwise the speed limit remained at the National Soeed limit of 60 Mph… is my recollection right or wrong ??
I don’t think that can be right, for two reasons. One is that many NSL dual carriageways begin at roundabouts or other junctions, so there will be no “dual carriageway ahead” sign - those only appear where a single carriageway road develops into a dual carriageway away from a junction. Another is that “dual carriageway ahead” is not a sign with regulatory or legal meaning, it is only for information, which is why it’s a rectangular sign with a blue background.
You state this yourself in this very article:
"2. There's a blue "keep left" sign at each end, which is the legal requirement for a dual carriageway to exist."
That’s not a “dual carriageway” sign, that’s a “keep left” sign that can be used anywhere you must keep to the left of something. I didn’t think that’s what we were talking about - when the other poster wrote about a “blue dual carriageway sign” that suggests to me the blue rectangular signs with the wording “dual carriageway ahead”.
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Picture credits
- Photograph of the A38(M) is taken from an original by Chris Whippet and used under this Creative Commons licence.
Conversely, an odd bit of road that looks like a dual carriageway, but isn't, can be found in the suburbs of Halifax. Cross Street West and Highfield Gardens run parallel to each other, with a wide grass verge between them, but they are two separate two-way streets.
To make things interesting, the local DVLA test centre exits onto Cross Street West, and the unusual layout provides multiple ways for unprepared drivers to fail their test within the first minute, particularly as Cross Street West usually has parked cars blocking one side, making it less obvious it's a two-way street.
https://www.google.co.uk/maps/@53.7297833,-1.890881,19z