Dual carriageway or no dual carriageway?

[jamei303]

Swervin_Mervin said:

Whether it is or not, there's signage to indicate it's d/c, but I'm guessing you know that

The signs don't make it a dual carriageway though.

[jamei303]

The TSRGD quoted above defines a dual carriageway as "a road which comprises a central reservation"

However the Road Traffic Regulation Act 1984 says a bit more:

“dual-carriageway road” means a road part of which consists of a central reservation to separate a carriageway to be used by vehicles proceeding in one direction from a carriageway to be used by vehicles proceeding in the opposite direction;

So I think a central reservation to separate vehicles waiting to turn right doesn't necessarily make a dual carriageway.

[Cat]

jchesh said:

Cat said:

The terms "single lane dualling" and "central reservation island" are not referred to in the legislation so relying on them to support your position is pointless.

They are both mentioned in this http://www.standardsforhighways.co.uk/ha/standards... cited earlier by Riley Blue, as follows: '1.16 Single Lane Dualling. An at-grade junction, usually a T- or staggered junction, within which central reservation islands are shaped and located so as to direct traffic movement (Fig 1/3).' [my highlighting]

That is not legislation and has nothing to do with whether a particular stretch of road does or doesn't meet the definition of a dual carriageway.

jchesh said:

Have I misunderstood you here then:

Cat said:

If it was a dual carriageway the warning signs would be for end of dual carriageway not as they are for 2 way traffic.

It would appear so. Signs don't define if the road is single or dual carriageway, its physical features do. If the physical layout meets the definition of a dual carriageway it should be appropriately signed. The road linked to in the OP doesn't have dual carriageway way related signs because it doesn't fit the definition of a dual carriageway.

Cat

[jchesh]

Cat said:

The road linked to in the OP doesn't have dual carriageway way related signs because it doesn't fit the definition of a dual carriageway.

Cat

...in your opinion. I would consider that extended section of kerbed grass a central reservation (or series of 'central reservation islands'); others would consider it a series of very large traffic islands. Hence this discussion.

The section of A5 I posted ( http://goo.gl/maps/2zT32GstXtq ) features an end of dual carriageway sign but nothing at the beginning of it (approaching from the SE) or to herald the beginning of it, not even a keep left sign. Would you consider that a piece of dual carriageway, and if so, what about it makes it one versus the OP's? I know that its central reservation is different from the OP's bit of A30 - it doesn't feature junctions and is longer, and has crash barriers - but nowhere in this thread has any of these differences been mentioned as a factor that determines whether a piece of road is dual carriageway.

Edited by jchesh on Friday 11th January 17:05

[PF62]

So going by the above this is definitely a dual carriageway -

https://goo.gl/maps/ZLfCgPQPRzz

No idea why it exists though.

[jchesh]

PF62 said:

So going by the above this is definitely a dual carriageway -

https://goo.gl/maps/ZLfCgPQPRzz

No idea why it exists though.

To physically prevent overtaking?

[Cat]

jchesh said:

...in your opinion.

And presumably that of the relevant roads authority who otherwise would have placed the appropriate signage.

There is a specific warning sign which guidance states should be used to indicate the end of a dual carriageway ahead. Any suggestions as to why, if, as in your opinion, the road is a dual carriageway the appropriate warning sign hasn't been used?

jchesh said:

what about it makes it one versus the OP's? I know that its central reservation is different from the OP's bit of A30 - it doesn't feature junctions and is longer, and has crash barriers

You've answered your own question, the layout of the two roads is completely different, one has a central reservation the other has a series of traffic islands.

jchesh said:

but nowhere in this thread has any of these differences been mentioned as a factor that determines whether a piece of road is dual carriageway.

Other than the fact that traffic islands are explicitly excluded as forming a central reservation.

Cat

[jchesh]

Cat said:

jchesh said:

...in your opinion.

And presumably that of the relevant roads authority who otherwise would have placed the appropriate signage.

There is a specific warning sign which guidance states should be used to indicate the end of a dual carriageway ahead. Any suggestions as to why, if, as in your opinion, the road is a dual carriageway the appropriate warning sign hasn't been used?

For the same reason that the bit of A5 I cited has none of the signs required for the start of a dual carriageway - shoddiness, a failure to comply with signage regulations.

They have, however, included the 'two-way traffic' warning at each end here, which are required in two scenarios: at the end of a dual carriageway and at the end of a one-way road. Since this isn't a one-way road, it's a......

Cat said:

jchesh said:

what about it makes it one versus the OP's? I know that its central reservation is different from the OP's bit of A30 - it doesn't feature junctions and is longer, and has crash barriers

You've answered your own question, the layout of the two roads is completely different, one has a central reservation the other has a series of traffic islands.

jchesh said:

but nowhere in this thread has any of these differences been mentioned as a factor that determines whether a piece of road is dual carriageway.

Other than the fact that traffic islands are explicitly excluded as forming a central reservation.

Cat

So because you've decided to call these 'traffic islands', that's what they are? Why are they not 'central reservation islands'?

Going back to the TSRGD definition of a central reservation,

(a) any land between the carriageways of a road comprising two carriageways; or

(b) any permanent work (other than a traffic island) in the carriageway of a road,

which separates the carriageway or, as the case may be, the part of the carriageway, which is to be used by traffic moving in one direction from the carriageway or part of the carriageway which is to be used (whether at all times or at particular times only) by traffic moving in the other direction

could you argue why those grass areas are not 'any land between the carriageways of a road comproising two carriageways'?

The hatched road markings leading up to each end of the grass areas, and the solid-edged hatched areas joining them up in between also make the whole lot look like a central reservation to me. If each area of grass were an island, wouldn't each one have a keep left arrow on? There's only one keep left arrow in each direction - at the beginning of the grassed area (aka central reservation, aka series of central reservation islands).

Edited by jchesh on Friday 11th January 18:32

[anonymous-user]

Cat said:

jchesh said:

Cat said:

The terms "single lane dualling" and "central reservation island" are not referred to in the legislation so relying on them to support your position is pointless.

They are both mentioned in this http://www.standardsforhighways.co.uk/ha/standards... cited earlier by Riley Blue, as follows: '1.16 Single Lane Dualling. An at-grade junction, usually a T- or staggered junction, within which central reservation islands are shaped and located so as to direct traffic movement (Fig 1/3).' [my highlighting]

That is not legislation and has nothing to do with whether a particular stretch of road does or doesn't meet the definition of a dual carriageway.

jchesh said:

Have I misunderstood you here then:

Cat said:

If it was a dual carriageway the warning signs would be for end of dual carriageway not as they are for 2 way traffic.

It would appear so. Signs don't define if the road is single or dual carriageway, its physical features do. If the physical layout meets the definition of a dual carriageway it should be appropriately signed. The road linked to in the OP doesn't have dual carriageway way related signs because it doesn't fit the definition of a dual carriageway.

Cat

It would seem odd (at least to me) if features built to make junction between a major road and a minor road safer had the automatic effect of raising the speed limit on the major road at that junction.

Whoever wrote para 2.24 of the Standards for Highways doc linked to upthread seems to think that single lane dualling doesn't result in an increased speed limit.

[zarjaz1991]

mac96 said:

Given that this thread has been debated since last night (by people with an interest in the subject) without reaching agreement, it would seem grossly unfair to a random driver to penalise them for exceeding the speed limit, assuming their speed was under 70mph.
Surely should have 60mph signs if that is the intention. I am not saying 'according to regulation X, there should be a sign'- I am saying you can't expect anyone to know what the limit is otherwise.

Prosecuting people isn't about what's fair, it's about what will secure a conviction.

[PF62]

jchesh said:

PF62 said:

So going by the above this is definitely a dual carriageway -

https://goo.gl/maps/ZLfCgPQPRzz

No idea why it exists though.

To physically prevent overtaking?

Yes, but why would you want to. It is a straight road with no junctions.

[TallPaul]

PF62 said:

jchesh said:

PF62 said:

So going by the above this is definitely a dual carriageway -

https://goo.gl/maps/ZLfCgPQPRzz

No idea why it exists though.

To physically prevent overtaking?

Yes, but why would you want to. It is a straight road with no junctions.

Its there because an overhead runway (or taxiway) was going to be built linking the two airfields. It was going to be the base for the supporting pillars but the project got cancelled after the road was modified.

[Cat]

jchesh said:

So because you've decided to call these 'traffic islands', that's what they are? Why are they not 'central reservation islands'?

I've explained why I believe they are traffic islands, the road layout in the OP shows that they are there not to separate vehicles travelling in opposite directions but to provide protection to traffic turning right and to allow it to do so without interrupting the progress of following vehicles.

'Central reservation islands' is not a term which features in the definitions of a dual carriageway so I'm not sure why you keep bringing it up.

jchesh said:

could you argue why those grass areas are not 'any land between the carriageways of a road comproising two carriageways'?

Certainly - the grass areas are bounded by kerbs so they fall within the permanent works definition not the any land definition.

Cat

[Cat]

jchesh said:

For the same reason that the bit of A5 I cited has none of the signs required for the start of a dual carriageway - shoddiness, a failure to comply with signage regulations.

Or the road designers and engineers knew that it wasn't a dual carriageway and so didn't sign it as one.

Cat

[jchesh]

Greg66 said:

It would seem odd (at least to me) if features built to make junction between a major road and a minor road safer had the automatic effect of raising the speed limit on the major road at that junction.

Whoever wrote para 2.24 of the Standards for Highways doc linked to upthread seems to think that single lane dualling doesn't result in an increased speed limit.

However, that same document says

Single lane dualling is formed by widening the major road to provide a central reservation, a right turning lane and space for vehicles waiting to turn right from the major road into the minor road (Fig 2/3).

If the section in question is a case of single lane dualling, then according to this document the grassy area is a central reservation, and therefore the section fits the description of a dual carriageway. Not a continuous dual carriageway, or a 'full' dual carriageway, but nevertheless a road with a central reservation i.e. a dual carriageway.

I think most have agreed that accelerating up to 70 through this area would not be the best idea, but nevertheless I am yet to be convinced that the speed limit in this section is 60 mph.

Edited by jchesh on Friday 11th January 19:50

[jchesh]

Cat said:

'Central reservation islands' is not a term which features in the definitions of a dual carriageway so I'm not sure why you keep bringing it up.

Because it's a term used in the design manual cited above in reference to single lane dualling (of which we seem to have established that this is an example), and 'central reservation' is a term used in the definition of a dual carriageway.

Cat said:

jchesh said:

could you argue why those grass areas are not 'any land between the carriageways of a road comproising two carriageways'?

Certainly - the grass areas are bounded by kerbs so they fall within the permanent works definition not the any land definition.

Cat

So, because you say so, kerbs = permanent works and no kerbs = any land?

I actually think that possibly the point (b) in that two-fold definition of a central reservation is to allow for situations where there is continuous tarmac across the whole road but with a structure such as a crash barrier acting as a central reservation. This is not the case here - there is a not-insignificant strip of 'land' between what to me look like two carriageways.

Regarding your point about these islands and their only function being to protect turning traffic - why then is there a section at the other end from the location brought up by the OP where the area extends far further than necessary for this, without any junctions either side?

You haven't addressed my point about the lack of a new keep left arrow per island and the fact that the islands are all connected by solid-bordered chevrons, which I believe makes the whole arrangement constitute a central reservation.

I am enjoying this debate even if it's a relatively academic one. Having said that, there must be a police force somewhere in the country who's thought of siting a fixed or mobile camera in an area of ambiguity like this, so perhaps for someone somewhere it hasn't been or won't be merely academic!

Edited by jchesh on Friday 11th January 20:12

[anonymous-user]

jchesh said:

However, that same document says

Single lane dualling is formed by widening the major road to provide a central reservation, a right turning lane and space for vehicles waiting to turn right from the major road into the minor road (Fig 2/3).

If the section in question is a case of single lane dualling, then according to this document the grassy area is a central reservation, and therefore the section fits the description of a dual carriageway. Not a continuous dual carriageway, or a 'full' dual carriageway, but nevertheless a road with a central reservation i.e. a dual carriageway.

I think most have agreed that accelerating up to 70 through this area would not be the best idea, but nevertheless I am yet to be convinced that the speed limit in this section is 60 mph.

Edited by anonymous-user on Friday 11th January 19:50

But there are numerous sections of road in central London with a central reservation: forex from the new US Embassy to Vauxhall Cross, Waterloo Bridge, Park Lane, Kingsway, the pinch points where one enters the City of London are just off the top of my head. They “inherit” for want of a better word the speed limits of the roads that feed onto them. Why would this layout be any different?

[Dr Jekyll]

Greg66 said:

But there are numerous sections of road in central London with a central reservation: forex from the new US Embassy to Vauxhall Cross, Waterloo Bridge, Park Lane, Kingsway, the pinch points where one enters the City of London are just off the top of my head. They “inherit” for want of a better word the speed limits of the roads that feed onto them. Why would this layout be any different?

Because the central London roads aren't NSL, so the question of dual or single carriageway doesn't affect the limit.

[jchesh]

Greg66 said:

But there are numerous sections of road in central London with a central reservation: forex from the new US Embassy to Vauxhall Cross, Waterloo Bridge, Park Lane, Kingsway, the pinch points where one enters the City of London are just off the top of my head. They “inherit” for want of a better word the speed limits of the roads that feed onto them. Why would this layout be any different?

Because the areas you mention are urban dual carriageways with prescribed speed limits (30 by default unless otherwise signed), whereas this is an area of National Speed Limit which varies by number of carriageways and by vehicle type.

[redjohn]

Cat said:

I've explained why I believe they are traffic islands, the road layout in the OP shows that they are there not to separate vehicles travelling in opposite directions but to provide protection to traffic turning right and to allow it to do so without interrupting the progress of following vehicles.
Cat

As above. It really isn't complicated.

A two mile dual carriageway with traffic island in middle to allow turn right does not make the whole dual carriageway a traffic island. Equally a traffic island that is extended doesn't make it a dual carriageway. It is just case of taking a holistic look at the purpose for the carriageway separation.