Viewing footage of the crash site on the BBC news website, it seems that the concrete barriers (Jersey Barriers?) didn't provide much, if any, resistance to the vehicles crossing the central reservation. I had assumed that they would have been at least capable of doing so. Weren't the metal armco barriers capable of this?
So what is the drive to concrete barriers for? Anyone know?
Cheers.
In article , David Paste writes
If you want to promote discussion on website footage, it might be an idea to provide a link to that footage or a news article.
Unless you bolted those concrete barriers together yourself then it would be nice if you had marked your post with an 'OT:' prefix.
or better still, post in the correct newsgroup.
In article , Andrew Gabriel writes
Fair comment but diy aside, this is fundamentally an engineering newsgroup.
Armco and tensioned wire barriers are designed to slow vehicles that impact them at a shallow angle, without throwing them back into the carriageway. They were never intended to resist a direct impact by a heavy vehicle.
They take up less width. The original specification called for a central reservation of at least 15 feet wide, which gave plenty of room for two rows of Armco. However, as motorways are being expected to carry far heavier traffic than many were originally designed for, central reservations and emergency vehicles lanes (aka hard shoulder) are being sacrificed to fit more lanes in.
Not especially. I have seen concrete mixers and the like go through them like they were not there. Bad one not far from me a few years back.
A house not far away used to regularly get partially demolished by armco penetrating muppets that entered a bend too fast. That hasn't happened since they replaced it with a solid concrete buttress so I guess they are more resilient. The new solid defences and >>>> livery would appear to intimidate people into slowing down for the tight bend.
Stopping cars and glancing incidence events. I doubt there is anything realistic you can do to stop a 40T HGV with a narrow central barrier if it is travelling at the speed limit and a closing angle >30 degrees.
I did wonder if the idea is to intimidate the outside lane. The only advantage they seem to have is that they block oncoming headlights more effectively than the armco but that is all I can see as an advantage.
I also think that the Armco barrers were too low for many modern vehicles where the CofG is too high. They roll over the barrier into the oncoming carriageway.
Interesting page here
and from it
On impact with a concrete barrier, any vehicle up to 13.5t in weight, which includes most buses, coaches and 4x4s, will be contained and redirected back to the highway. Steel barriers, on the other hand, are only able to contain a 1.5t car, such as a Ford Focus.
That would be the standard familiar "Armco". I don't think many people realise how limited its capacity is.
There is a slightly stronger version which is an open box section, and there are also assemblies with multiple horizontal members, sometimes seen protecting bridge supports, or preventing incursion onto railway tracks.
Chris
They built a new bypass near here a few years ago (the "New Thanet Way") and the opening was delayed by a day when they realised they needed the multiple one in front of a large electricity pylon! And this is a very solid pylon - an "end of the line" one with cables down to a large substation. Hate to think of the consequences if that were hit.
Not really a problem in the days when few cars weighed over a ton and there were two rows of Armco, on a wide central reservation.
Note that the concrete barrier redirects the vehicle back onto the carriageway, while Armco was intended to keep it from doing that, to reduce the risk of it colliding with another vehicle.
Wrecking more cars so they can sell new ones? I'd imagine the cheaper the barriers can be built the better. However the ones you mention which used to be the norm give and buckle to absorb the energy, Concrete does not it seems.
Brian
I think it's perfectly in order to post here about such things.
Bill
I read somewhere that this was now seen as a benefit; Armco supposedly slows stuff down more quickly than a glancing impact with concrete, so that with Armco any secondary impacts are more severe, with more chance of multiple shunts. With modern car construction and airbags, being side-swiped by something bouncing off the concrete might be more survivable.
From the third photo here
it looks as though they are simple gravity structures, not tied down to the ground at all.
In article , newshound writes
Thanks for the link.
In that respect they would be similar to the tensioned cable crash systems where the cables are only fixed and tensioned at something like km intervals. In-between, some cables weave in and out of the relatively light supporting poles and I think there are others that rest in deep U shaped cups on top. They absorb the energy by dissipating it along a long length.
I'm not familiar with the particular thin design in the pics but wider ones in temporary use on motorway roadworks are keyed and bolted through with multiple 20 odd mm studs to form a long continuous barrier and gain a similar effect.
I suspect, and the pictures appear to indicate, that the individual slabs are fixed together and that in the extreme forces of the collision, the barrier gave way. I'd suggest that nothing short of tank traps will stop a 32 ton artic and there needs to be some kind of cost - benefit trade off.
I don't think other barrier types would have survived or performed any better.
There was a documentary programme a very long time ago that showed the testing and evaluation they carry out on new crash protection systems. They are very thorough and do actually crash fully laden vehicles into them at the speeds and angles that they are designed to resist.
Those look like the temporary type used during roadworks, rather than the continuous slip-formed barriers.
Whilst sawing motorcyclists into small pieces.
Not being hit by something not bouncing off the Armco is even more survivable.
I'm thinking of Ronan Point, and I wonder whether an enquiry will find that some/many of the bolts were not properly tightened, or even bolted at all.
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