Armco vs concrete barrier

[PeterA5145]

The safety barriers on the M56 Sharston Spur are currently being replaced, but in the central reservation they're re-installing conventional armco. This seems to go against the current trend for using a concrete barrier.

Does anyone know what the criteria are for deciding which to use in new schemes? Is it maybe something to do with D2 vs D3 roads?

[wrinkly]

My guess in this case is that it's a matter of sightlines. The road is quite curvy and the central reservation is not very wide. It may be that in order to maintain the specified visibility distance you have to allow drivers to see over the central barrier.

There's a stretch of Armco barrier remaining around M1 J33 which I suspect may be for the same reason.

[Bryn666]

DMRB specifies concrete step barrier on the basis of traffic volumes.

The M56 here certainly should have one but a departure from standard will have been sought; entirely on cost grounds it seems because the only thing stopping the barrier being concrete is the presence of existing street lighting which would have to be reinstalled on top of the barrier due to extremely restricted verges.

Area 10 really can be embarrassing sometimes.

[wrinkly]

So what's the reason in the M1 J33 case?

[Bryn666]

I would imagine cost, as is usually the reason for these things.

With the exception of smart motorway schemes where has a motorway recently been retrofitted with a step barrier?

[Pendlemac]

I would imagine cost, as is usually the reason for these things.

With the exception of smart motorway schemes where has a motorway recently been retrofitted with a step barrier?

M65 J10 - J14 ( Which is the section NOT under HE control. )

[Conekicker]

So what's the reason in the M1 J33 case?

I think it's to do with how the centre piers of the junction bridges are constructed, something to do with them being articulated at the base. I hasten to add that I'm not a bridge engineer and could well be wrong.

[Bryn666]

I would imagine cost, as is usually the reason for these things.

With the exception of smart motorway schemes where has a motorway recently been retrofitted with a step barrier?

M65 J10 - J14 ( Which is the section NOT under HE control. )

Of course! Although as a non-trunk motorway it's excluded

[darkcape]

I would imagine cost, as is usually the reason for these things.

With the exception of smart motorway schemes where has a motorway recently been retrofitted with a step barrier?

Quite a few when the Armco is expired...M54, parts of the M1 near J20, M42 south of J10, probably loads more I can't remember now.

So what's the reason in the M1 J33 case?

I think it's to do with how the centre piers of the junction bridges are constructed, something to do with them being articulated at the base. I hasten to add that I'm not a bridge engineer and could well be wrong.

The bridges look like they have precast beams sat on the piers so I'd expect the movement joint to be at the top of the piers. It does look like the street lighting for the overbridges are in the M1 central reserve, and there are also drainage pipes running down the piers - perhaps there were drainage chambers that couldn't be relocated.

[wrinkly]

With the exception of smart motorway schemes where has a motorway recently been retrofitted with a step barrier?

A1(M) from J59 to a mile south of J60, currently in progress.

Previously it was tensioned wire, like most of the stretch from J59 to Chester-le-Street.

[wrinkly]

With the exception of smart motorway schemes where has a motorway recently been retrofitted with a step barrier?

A1(M) from J59 to a mile south of J60, currently in progress.

Previously it was tensioned wire, like most of the stretch from J59 to Chester-le-Street.

Now well advanced, due for completion circa November. My guess is that this might be the first phase of a programme to replace all the wire barrier on the A1(M) in the NE with concrete, with a phase every year for 5 or 6 years.

Some random short bits towards the north end have already been done, possibly as repairs?

[Halmyre]

A large-ish stretch of the M90 around Kelty has just had its tensioned wire replaced by shiny new Armco. Has tensioned wire been declared not up to the job? Looking at GSV, it does look pretty insubstantial.

[wrinkly]

A large-ish stretch of the M90 around Kelty has just had its tensioned wire replaced by shiny new Armco. Has tensioned wire been declared not up to the job? Looking at GSV, it does look pretty insubstantial.

No idea but the stuff that's being replaced on the A1(M) is probably about 48 years old. What's its lifespan?

There's still a lot of tensioned wire on the A74(M) and the M62 J22-23.

[NICK 647063]

I think the powers that be are very keen to get rid of tension wire as it’s basically a cheese wire to motorcyclists, I suspect it’s replaced as it becomes life expired, still a good section of it on the M1 around East Leeds.

In the last year or so Armco barrier seems to be getting installed at quite a rate, I know the A64 just had all it’s central barrier renewed from the A1(M) to York but is now also getting new verge barriers from Tadcaster to York which are Armco, really not sure why this section is getting barriers along the full verge it’s pretty level with the adjoining fields, seems HE have got a cheap deal on Armco.

I did also raise the question about expressways needing concrete central barriers and HE response was pretty shortsighted, they did confirm the A64 was a planned expressway and when this is upgraded the section from Tadcaster east to York will need significant reconstruction to provide alternative access to and from adjoining properties at which time a concrete barrier would be installed but surely the A1(M) to Tadcaster East is already up to standard so a concrete barrier would have made sense instead of Armco but the response was it will come from a different budget, this was simply a like for like renewal.

[Owain]

My guess in this case is that it's a matter of sightlines. The road is quite curvy and the central reservation is not very wide. It may be that in order to maintain the specified visibility distance you have to allow drivers to see over the central barrier.

There's a stretch of Armco barrier remaining around M1 J33 which I suspect may be for the same reason.

DMRB specifies concrete step barrier on the basis of traffic volumes.

The M56 here certainly should have one but a departure from standard will have been sought; entirely on cost grounds it seems because the only thing stopping the barrier being concrete is the presence of existing street lighting which would have to be reinstalled on top of the barrier due to extremely restricted verges.

Whatever the reason - traffic volumes, or cost - I think that sight-lines should always be taken into consideration!

In Britain we used to be very good at this; there are many sections of motorway where there is a hatched area wide enough to add an extra lane next to the central reservation - such as the M5 in Worcestershire, before it was smartified - or a wide grassed area before the barrier. Both of these features used to provide excellent vision of the road ahead for traffic in the outside lane. Sadly, this seems to have disappeared on the section I'm thinking of on the M5 because of the smartification, which resulted in a fourth lane being added.

The width of many British central reservations - or the width of the carriageway thanks to the inclusion of a hatched area next to the reservation - often compares very well with many of the Italian roads I've driven, where the outside lane can be quite terrifying at speed on account of the proximity of the barrier. This is often the case, irrespective of whether the barrier is armco, such as here, or here, where it is concrete. In both cases, where the driver of a car is obviously seated much lower than the camera on the Google car, the proximity of the barrier to the driver significantly reduces the sight-line, and I've often found it an advantage to be driving my own right-hand-drive car rather than a left-hand-drive hire car!

[Johnathan404]

I think the powers that be are very keen to get rid of tension wire as it’s basically a cheese wire to motorcyclists, I suspect it’s replaced as it becomes life expired, still a good section of it on the M1 around East Leeds.

I think the cheese grater thing is exaggerated. Whether it’s a tensioned sure or an Armco, the posts will cause life-threatening injuries anyway.

[Glenn A]

A large-ish stretch of the M90 around Kelty has just had its tensioned wire replaced by shiny new Armco. Has tensioned wire been declared not up to the job? Looking at GSV, it does look pretty insubstantial.

No idea but the stuff that's being replaced on the A1(M) is probably about 48 years old. What's its lifespan?

There's still a lot of tensioned wire on the A74(M) and the M62 J22-23.

Speaking of the A74, long sections of the old D2 were like this well into the eighties and there were several serious accidents involving vehicles skidding across the grass central reservation. Tensioned wire might not be brilliant, but this former section of A74 looks lethal.
http://www.geograph.org.uk/photo/289855

[jabbaboy]

Speaking of the A74, long sections of the old D2 were like this well into the eighties and there were several serious accidents involving vehicles skidding across the grass central reservation. Tensioned wire might not be brilliant, but this former section of A74 looks lethal.
http://www.geograph.org.uk/photo/289855

https://goo.gl/maps/oFAdUSQWGZL2 - There's still a bit of the A19 like that, assuming there's no barrier there so you can see what's coming out of the junctions at Sheraton.

[Bryn666]

I think the powers that be are very keen to get rid of tension wire as it’s basically a cheese wire to motorcyclists, I suspect it’s replaced as it becomes life expired, still a good section of it on the M1 around East Leeds.

I think the cheese grater thing is exaggerated. Whether it’s a tensioned sure or an Armco, the posts will cause life-threatening injuries anyway.

The wire could potentially rip a limb off but colliding with a Z post WILL cause substantial internal injuries and likely blunt force trauma resulting in death.

[mikehindsonevans]

I think the powers that be are very keen to get rid of tension wire as it’s basically a cheese wire to motorcyclists, I suspect it’s replaced as it becomes life expired, still a good section of it on the M1 around East Leeds.

I think the cheese grater thing is exaggerated. Whether it’s a tensioned sure or an Armco, the posts will cause life-threatening injuries anyway.

It has always been my experience (witnessed on two occasions over the decades) that motorcyclist versus stationery object at 70mph is usually a 1-0 result and a call to the organ-donor team. A solid, smooth, concrete barrier gives the (fractional) chance of bouncing back onto the carriageway, shedding speed and shredding leathers.

Not sure what the ultimate answer is, but instinctively I'd vote for solid barriers between carriageways; it also gives our eyes *some* respite from the "let's light up the next count(r)y" LED floodlights which some modern cars seem to have. Oh lord, I'm turning into a grumpy middle-aged man!