We already knew that the M4 around Newport (between J24 and J28) was getting Variable Speed Limits, but I have just come across this document (dated April 2010 and containing a map) which shows that further measures are proposed:

This was linked to from this page but it does not really have any further details on these new proposals.

Anyone know any more, or have any comments on the new proposals?

As the Artilleryman said in War of the Worlds side 2: This is my territory

Widening between Junctions 27 (High Cross) and 26 (Malpas)
Yes this is being done. The central reservation is currently a big concrete block, and the VSL signs are slowly being installed.


Widening between Junctions 29 (Castleton) and 28 (Tredegar Park)
This was completed recently as an extra phase of the 29-32 widening, complete with new bilingual (i.e. Llundain) signs.

Hard shoulder running/widening between Junctions 28 (Tredegar Park) and 27 (High Cross)
Again, this is a building site at present. Lots of cones. Narrow lanes at the moment with the HS completely blocked off. They were ripping trees down the other day so I'm assuming they're going to demolish the retaining wall and move it back.

Improvements to Junction 29A (St Mellons)
Done - new signs on Westbound and new merge/tigertailing on eastbound.

Modification to Junction 27 (High Cross)
I think this is just improving the merges as a result of the new widening either side.

Modification to Junction 26 (Malpas)
See above.

Modification to Junction 25 (Caerleon)
God knows what they're doing to this - although there is a new Sainsburys in the vacinity, so it may be linked to creating link roads for that. This junction should just be levelled and started again, it's completely wrong in EVERY way.

In what way is J26-29 being "widened"? It is already D3M with discontinuous hard shoulder, so are they going to widen it to D4M, or just make the HS continuous? Even doing that would be expensive, because there are bridges where only 3 lanes fit under them, so they would need to be demolished and rebuilt...

I look forward to anyone suggesting that they merely widen the road at Brynglas....

Is the Welsh Assembly affected by the spending cuts? If not, I suppose it's feasible to widen the tunnels so long as all other road projects planned for the next 10 years are cancelled

Seriously though, a more realistic option is to mark out the existing tunnels each with three very narrow lanes and have a permanent SPECS enforced 20mph limit

But even better to follow Plan A: convert the M4 to the M48 as we have discussed on here many many times- and build a new M4 south of Newport.

No widening has taken place or is currently taking place!

Aren't they going for the cheap option with the Llanwern Steelworks road?

"Bows and arrers against the lightning!"

Ulla!

I've said it before and I'll say it again: the cheapest solution would be to buy out the small number of houses that remain on top of the tunnel and turn it into an open cutting. Then you can make the motorway as wide as you like down there. There's barely anything left on top anyway, thanks to the subsidence the tunnels have caused.

If you really want to, you can make it a cut and cover tunnel once you're done widening and restore the land on top.

That has to be cheaper than a southern bypass.

Would it be possible to convert the tunnels into an open cutting over the space of, say, a weekend closure? I think the need to keep the M4 open would be the biggest barrier to Chris's suggestion.

Interesting question, and there has to be some good reason why this hasn't actually been considered by those in charge. Not sure if it's just politically unacceptable to turf out the residents of what appears to be quite a nice area of Newport or if there really are some serious engineering problems to overcome.

However, one thought that occurs is that the tunnels have thick concrete linings. Would it be possible to excavate everything on top while leaving the actual tunnel structures intact? You can then do a weekend closure or a series of overnights or contraflows or whatever else, in order to dismantle that concrete shell.

Again, I'd be very interested to hear what those with civil engineering knowledge make of it as an idea.

It's certainly novel.

The other option is of course a third bore for tidal-flow purposes... but with the Usk flyovers to the east that would be very exciting to see put in place!

Interesting idea. Looking at the overheads, it would involve demolishing upto 10 houses and a hotel, as well as building a bridge for Brynglas Road (Brynglas Avenue could be rerouted to avoid a second bridge). You would probably have to build an access road for construction, but there looks to be space for a suitable road from the A4051. Certainly looks like a feasible plan, as long as you could excavate the hill without disturbing the motorway. Of course, the fear of a tunnel collapse would probably kill the plan - I wouldn't like to be the person who signs off the risk assessment for that !!!

Jim.

I wouldn't go so far as to describe that area as quite nice -- it's a bunch of hastily thrown up houses that seem to derive most of their structural integrity from pebbledash. The reasonable stuff is what they put junction 26 through as much of as possible (why on earth didn't they use loops here?).

My suspicion as to why the obvious solution hasn't been adopted is just how deep the cutting would have to be -- taking the difference between 12m above sea level at the canal towpath west of J26 and 49m at the junction of Brynglas Road and Brynglas Avenue, we're looking at a cutting about 120ft deep -- that's getting on for being a similar scale as the massive ones on the M62. That would need some serious retaining walls and probably some sort of cross-bracing.

Does anyone know why sets of traffic lights (one per lane) have been put into the VSL gantries at the entry portals to the Brynglas tunnels, complete with massive traffic light warning signs?

EDIT: Found reference to it here but not much else:
http://www.pistonheads.co.uk/gAssing/to ... 20on%20M4!!

It seems to be the done thing where tunnel works are happening - presumably it's a way to quickly stop traffic in an emergency, that motorists will readily understand. The A1(M) at Hatfield has had traffic lights both ways, always showing green on the occasions I've been through, for at least 18 months now while the tunnel refurbishment works are ongoing.

Ditto all the A55 tunnels- either green arrows or a normal set of traffic lights at each entrance and always on green when I go through.

Used the M4 round Newport a few days ago. Noticed after all the gantries there are "Gatso markings". On my return I was surprised to find the motorway between junctions 24 and 28 open after 8pm. A lane was closed and the overheads were showing 40.

Hi Jam35. I live in one of those houses that were hastily thrown up and rely on pebbledash for structural integrity above the Brynglas Tunnels. One of the houses that are now being threatened with demolition. Anyway I am officially inviting you to my disposable trash home in this godforsaken awful area so you can explain to my wife and child that their home that I have worked so hard to create is just a minor inconvenience to be demolished to make a road a bit wider.