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The problem with repeaters is that it still is not clear whether it is a single or dual carriageway. There are certainly dual carriageways with a 60 mph limit (indicated by a ). This does not pose an issue of understanding the limit for car drivers - 60 mph is the limit, but since it's 40 mph for HGV's on a single and 50 mph on a dual, this doesn't help them much. They still have to stick to the lower limit, whether the sign says or .Similarly a lower limit applies to towing vehicles etc. and this is different for single and dual carriageways.

Not sure if I see the room for doubt in that definition, Ian. Under part (a), any strip of land which is not part of the carriageway makes a D/C. Under part (b) a (say) concrete barrier would be a "permament work" (therefore D/C) but a line of posts is not (therefore S/C).

That's not right.

A dual-carriageway is a road with some physical obstruction between the 2 carriageways - be it a raised kerb, grassy area, fixed armco barrier etc. This applies regardless of the number of lanes the road has in each direction. A dual-carriageway has a NSL of 70mph for cars regardless of whether it has a fixed crash-barrier or not.

Painted lines don't count.

OK.

My point is that by putting up 60mph signs rather than the NSL, you effectively change the speed limits for HGVs.

This is perilously close to a circular definition. Any land between the carriageways makes it a dual carriageway, but ONLY if it's a dual carriageway already?

No you don't. Many single-carriageway roads have 50mph limits, yet the limit for HGVs is still 40mph, regardless of the 50 signs.

In the UK, a specific speed limit sign can never raise the limit above the national speed limit for a certain vehicle.

The Highway Code says

103: You MUST NOT exceed the maximum speed limits for the road and for your vehicle [referring to the national speed limits].

There are some categories of vehicle whose national speed limit is less than 20mph on some roads, so the presence of any speed limit signs doesn't raise their limits above their NSL any more than a 60 sign does to an HGV on the A556.

That's another one I use from time to time and invariably see traffic going faster than the limit. That bit of the A30 from the Crooked Billet up to the airport as well, though not as fast there. Then there's the Egham bypass, particularly the eastbound bit. Actually quite a few round the Staines area, isn't there?

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For the sake of argument :



Would that include land at the same level and covered in tarmac? Basically, would this (cobbled together from Highway Code images ) be a dual carriageway?



Physically it's clearly a single piece of tarmac, but each pair of lanes is marked by a solid white line which, according to the Highway Code, defines the edge of the carriageway. If there's any road like this in the real world defintion (a) would presumably make it a dual carriageway even though there's nothing between the two but paint and tarmac. A 70 NSL then?

Edit: OTOH presumably this almost identical layout would be a single carriageway and have an NSL of 60, even though the painted markings are the only difference.

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Make everything as simple as possible, but not simpler - Einstein

Maybe so. What you do however is create sufficient uncertainty so that the presence of such signs can be used as a defence.

So said the legal advice to the Highways Agency at the time.

This is a great thread as it shows just how poor our understanding is of what is the applicable speed limit. If a dual carriageway is so poorly defined then what hope have we got? Still "Ignorance of the law is no excuse".

To follow up Gatsobait's question, what would be the correct interpretation if the hatched area in the second sketch had solid lines around it instead of broken lines?

In my experience, very few people know that there are two sorts of hatched "island" type markings anyway.

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Malcolm W.
The views expressed in this post are personal opinions and do not represent the views of Safespeed.

No. Paint doesn't count. It's one continuous carriageway (and besides, I think that this road layout would need hatching - as I don't think TSRGD 2002 would prescribe this layout without hatching).

In reality, it's the same situation as shown below



The number of lanes in each direction is irrelevant. All that is different (apart from the number of lanes) is that the gap between the white lines is smaller. This road is a single-carriageway, and would have an NSL of 60mph for cars.

Nice pictures there Gatsobait!

The second one is quite close to being a 5 lane single carageway, would it really be legal to have 5 cars going in the same direction there?

I would agree with your descriptions.
A road does not have to have tarmac on it to be a road. You can physically drive on tarmac, you can also physically drive on grass. If you have a tank you can physically drive on armco
It's the definition of what is the carageway that is important.

Push the top one together and you get a double white line...

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Andrew.

But you can only have land between the carriageways if a road has at least two of them

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

I don't think it is poorly defined, to be honest - the problem is that a lot of people don't understand the definition, which is not the same thing.

Also that some modern road markings tend to blur the distinction in people's minds.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

Just as long as the lanes travelling in different directions are not on the same piece of tarmac it is a dual carriageway. A relatively narrow grass verge without any kerbs can be classified as a central reservation.

Hmm. I've had a beef with this wording in the HC for a while.

What it actually says is those are the speed limits for those types of vehicle unless signs show otherwise. I would definitely interpret that as meaning that a 60 sign means 60 applies to all vehicles, rather than their NSLs.

I know the HC isn't law, and the actual law is clearer, but I think the HC is misleading.

Thanks, but it's just a combination of images from the "along the carriageway" section here. I can't take much credit for nicking them off the HC site and playing around in Photoshop.


Not what I intended. I should have put some arrows on it to show what I meant, but you have the two lanes on the left going in the same direction of travel and the two lane on the right going in the opposite direction. Each pair sits between solid white lines defining the edge of carriageway, making the middle No Mans Land rather than another lane.


AFAICT if it was it would be a dual carriageway due to the solid single white lines at the sides of each pair of lanes. I don't think they can be treated as synynomous with double white central lines as they seem to be wider sometimes and have rumble strips embedded in them. But if it's a layout that is not permitted by the regulations you mention then it's a moot point. If it can't exist it's kind of irrelevant. With dashed hatching it becomes much the same as my second image, in which case it's unquestionably a single carriageway. With solid hatching... ? Does a solid line around hatching indicate a border to the hatching or the edge of the carriageway? If the former, which is what I think, then it would always be single carriageway when there's hatching down the middle whether with solid or broken lines.

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Make everything as simple as possible, but not simpler - Einstein

Having a rethink about this, and Observer's sotonsteve's and Peter E's views, and the implication in the above definition, I am now inclined to the view that one carriageway means from edge to edge of the same piece of carriageway, irrespective of paint. Two carriageways (dual carriageway) would have to have some physical change of surface between them.

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Ian

Fair definition of dual carriageway on

http://en.wikipedia.org/wiki/Dual_carriageway


Not quite so informative - but worth a look see all the same is:

http://www.passplus.org.uk/modules.asp

Grass, kerbing, continuous barriers constiutute a central reserve whish physically separates each direction of the the carriageway. If there is only paint - solid line/hatch or broken line/hatch or red paint between these road lines or simply a double white line.... it's a single carriageway and the single carriageway NSL of 60 mph then applies.

Do think European NSL signage has the edge over the UK here given the differering NSL for goods vehicles exceeding 7.5 tonnes, coaches/buses above 12 metre length, and caravanners/trailers ...in that there sign does depict a lorry in the centre thus reminding of the speed limit difference.


As rule of thumb - tend to regard the carriageway on any road or direction of each carriageway in the case of a dual as the tarmac between each side of the solid white which usually runs alongside the kerb - at the edge of the road or carriageway (usual on A roads and dual A (M) roads) , and from edge to edge in the absence of such paint

Useful boook to supplement Highway Code, Road Craft and other books on improving driving is

"Know Your Traffic Signs" - yellow book published by the DfT and published by HMSO. ISBN 0-11-552612-3 on my copy - eigth impression 2003 and not updated as far as am aware.

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So my first hypothetical one would not be a dual carriageway (and now that I think about it I seem to recall the Ashton Expressway is considered a single carriageway and isn't a lot different in principle to that first image). But this would be a dual carriageway because of the surface change in the central reservation, right?



Incidentally, this is about what the bit of the A320 that I mentioned earlier used to look like before the barriers went up and the limit went down. Presumably if they'd carted the gravel away and tarmaced over the whole instead they'd have turned it into a single carriageway?

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Make everything as simple as possible, but not simpler - Einstein