M4/M5 Almondsbury/Filton 'Improvements'

[Jonathan B4027]

Up until Charlton Hayes really kicked off, there was still some of it to be seen on the ground. Google Earth wound back to 1999 shows the line better with the mobile home area built on top.

[jackal]

From a recent NH report:

Severn Resilience Package -
Developing a package of possible improvements to sections of the M4, M5 and M32
on the eastern side of the Severn Crossings near Bristol. This project is currently on
hold pending review of the traffic flow impacts of removal of the Severn tolls.

[AAndy]

A video both ways on the M4 of the barrier works current progress between the M32 and M5 junctions : https://youtu.be/Vi9UElO0Q5c

[DB617]

You know, I never thought to ask - does anyone understand the purpose of the central barrier replacement? They didn't seem to be out of life. Is it just the increased crashworthiness? It's a strange one, because I cannot quite see how smart motorways would require crossover prevention any more than conventional - or is it compensation for the narrower lanes?

[nowster]

You know, I never thought to ask - does anyone understand the purpose of the central barrier replacement? They didn't seem to be out of life. Is it just the increased crashworthiness? It's a strange one, because I cannot quite see how smart motorways would require crossover prevention any more than conventional - or is it compensation for the narrower lanes?

In general, it seems that Armco is no longer favoured as it can't contain HGVs from crossing over to the other carriageway as well as continuous concrete can.

[Chris5156]

You know, I never thought to ask - does anyone understand the purpose of the central barrier replacement? They didn't seem to be out of life. Is it just the increased crashworthiness? It's a strange one, because I cannot quite see how smart motorways would require crossover prevention any more than conventional - or is it compensation for the narrower lanes?

I think one aspect is that, if you're setting up roadworks for 2+ years to install a Smart Motorway, it's best to roll up as much other maintenance and renewal work as possible into that, so it's all done in one hit. One of the reasons Smart projects started to take longer and longer, and cost more and more, is that they started to be bundled up with central reserve works, drainage renewal, earthworks reconstruction and a load of other opportunistic works. Some of those might not have been needed for a few years, or even longer, if you're setting out the cones and spending the money you might as well do it in one shot.

All of which seems remarkably sensible until you consider the number of Smart schemes that declined to replace the existing carriageway, leaving all sorts of burned-off markings and rough patches everywhere, only for new roadworks to be set out shortly afterwards for resurfacing. You can't win them all.

[MotorwayGuy]

You know, I never thought to ask - does anyone understand the purpose of the central barrier replacement? They didn't seem to be out of life. Is it just the increased crashworthiness? It's a strange one, because I cannot quite see how smart motorways would require crossover prevention any more than conventional - or is it compensation for the narrower lanes?

I think one aspect is that, if you're setting up roadworks for 2+ years to install a Smart Motorway, it's best to roll up as much other maintenance and renewal work as possible into that, so it's all done in one hit. One of the reasons Smart projects started to take longer and longer, and cost more and more, is that they started to be bundled up with central reserve works, drainage renewal, earthworks reconstruction and a load of other opportunistic works. Some of those might not have been needed for a few years, or even longer, if you're setting out the cones and spending the money you might as well do it in one shot.

All of which seems remarkably sensible until you consider the number of Smart schemes that declined to replace the existing carriageway, leaving all sorts of burned-off markings and rough patches everywhere, only for new roadworks to be set out shortly afterwards for resurfacing. You can't win them all.

I seem to remember the when the widening of the M25 in Essex was completed, the surface looked like something you'd expect to find in a third-world country, with patches of old and new surface strewn with burnt off markings and filled in stud holes. I can't seem to find it on Google so it must have been resurfaced within a year of completion.

[KeithW]

In general, it seems that Armco is no longer favoured as it can't contain HGVs from crossing over to the other carriageway as well as continuous concrete can.

Indeed, they busily replacing the Armco on the A1(M) north of Darlington with concrete apart from the mass the concrete is apparently more likely to deflect an out of control back into the running lane rather break through it causing a head on collision, they also require less maintenance.

[DB617]

I contacted National Highways a few days ago with some nitpicks regarding this scheme, as I have been driving through their TM every day:

A couple of issues have been raised... firstly, the overhead gantry on the eastbound M4 just before J19 suggests - in contradiction with the yellow temporary signs - that two lanes leave for the M32. As the road carries a lot of tourist, far field and European traffic it's likely that many are not going to realise in time that there is actually a lane gain before the junction and it seems to be causing lots of drivers to make last minute panic lane changes. Surely get the gantry covered properly to reduce congestion and bad lane changes?

Secondly, the lane arrangement: why retain three lanes through J19 westbound when there are two lanes joining at the other side - making it a five-into-three lane motorway merge? Don't the joining and leaving traffic numbers justify a lane drop so the main carriageway through the junction is D2 and joining traffic could benefit from a tiger tail lane gain, thereby reducing the number of merge points on the mainline by one? Was this considered in planning?

On the eastbound side, is there a reason the mainline regains its lost 3rd lane just before the M32 >M4 EB onslip rather than the onslip becoming lane 1? My experience so far is that drivers (illegally, of course) begin to accelerate to NSL as the 3rd lane inexplicably reappears from lane 2 (I am aware that this is also how it was before the roadworks... again, inexplicably), and also because of the 2m width restriction on lane 3 through the roadworks, HGVs coming through the junction are piped into lane 1 in conflict with the joining traffic?
I must admit here, I am basically criticising them for maintaining the original layout. However if you drive through the works and compare it to the old StreetView you will notice that lane 2 splits into lane 2 and 3 almost at the same time as the slip road rises to meet the motorway, whereas it used to split right after the M32 lane drop. There's just a lot going on for drivers merging in and I stand by my comment about HGVs being spat into conflict. When the works first started I didn't realise the HGV drivers were trapped in lane 1 and didn't take the risk seriously when one was keeping pace with me as I joined and got a horn blast.

I am concerned - and wish to put it on the record if nothing else - that the merge arrangement is substandard and bordering on dangerous in places. At best, it is my experience that it is causing excessive congestion at peak times, and I say that having driven frequently through some of the similarly challenging M1 ALR schemes such as the A42/M1 complex.

It is my feeling, and I'm sure I'm not alone in this, that the priority has been placed on maintaining the existing lane configuration as much as possible through M4 J19/M32 J(0?) without due regard for the extra complications of the roadworks - meaning you have inherited the terrible bodge job made of J19 on the DHSR scheme.

Thank you for your email of 6 July 2023 regarding the overhead gantry signage on the eastbound M4 before junction 19 and the lane arrangement. We’re sorry you find our signage unclear and appreciate you raising this with us. We’re also sorry to hear you feel our lane merge arrangement at junction 19 westbound is substandard and could be causing safety concerns, as well as congestion.

I’ll try my best to answer each point you raise and explain why we’ve taken the decision to configure the lanes and signage in the way we have.

The first point you make is about the overhead gantry on the eastbound M4 just before J19 suggests and you feel contradicts the yellow temporary signs. Your suggestion to cover the gantry sign is a very valid one, but unfortunately, we are unable to do this. We are limited to what we can and can’t do with the existing overhead gantry signage, as such, we’ve had to reach a compromise between practicality and safety. In terms of the lanes, there are two lanes which can exit for the M32 from the M4 eastbound, both access this slip road.
They never really explained why they can't properly cover the signs. Perhaps some of our temporary works experts might understand the rules here a bit better. Also, to be fair, covering the signs may not entirely work as 'locals' and regulars might still assume that LBS1 and LBS2 both exit with the M32 leaving one mainline lane.

The second point you raise is concerning the lane arrangement: why retain three lanes through junction 19 westbound, when there are two lanes joining at the other side? We’ve had to maintain three running lanes on the M4 westbound above junction 19 due to daily traffic volumes reaching 55,000 per day. If we reduced the M4 westbound at junction 19 down to two lanes, we’d see extreme queuing at junction 19 back towards junction 18. The traffic flow and volumes just wouldn’t cope. With regards the M4 junction 19 westbound entry slip road, we’ve designed this in order to maintain the existing two lane merge, again to allow as much capacity flow as possible, albeit with a slower, controlled and safer environment. We have not made any decisions lightly, we have looked at all possible options and considered many factors, and our final layout went through a detailed design-stage process.
I felt like this shows a fundamental misunderstanding of what restricts capacity. Having three lanes across the junction bridges would be nice, but even nicer for the 55k VPD would be not having to slow to <5mph for the double merge at the onslip. Over-capacity onslips are really common across the network and cause far more delay than an early warning of a lane drop, but the long tiger tail and DHSR used to go a long, long way to addressing that on the M4 and perhaps lulled the contractor into a false sense of security. As far as the need to merge over into LBS2/3 goes, there are two miles between J19 and J20 for that to resolve itself. Which is more than you can say, for example, between Lofthouse Interchange and the M621 in Leeds.

Their argument also doesn't hold water when on a rail strike day or just about any Friday, the M4 now backs up most of the way to J18 which is approximately 5 miles, the congestion clearing about 200 yards after the merge. I suppose it does function as an excellent throttle, reducing the flows through the 3-lane section, but it most certainly does not relieve a possible bottleneck as it actually is the bottleneck...

The final point you make is concerning the eastbound side, is there a reason the mainline regains its lost third lane just before the M32 >M4 eastbound on slip, rather than the on slip becoming lane one? We’ve tried where possible to maintain the existing road layout, wherever possible, taking into consideration design capacity.
Again... quite the cop out, but I'll admit that they did almost maintain the existing road layout. The 2 up to 3 lane gain eastbound on the M4 above J19 is an abomination but not really the contractors' job to change. However I would argue that they have the power to make changes for the duration of the works that increase the safety within their area of responsibility, even if they have to reinstate an awful bodge afterwards.

I am honestly quite pleased that the PR department here took the time to reply to me. I emailed fully expecting to be ignored as a busybody, so I must have spoken at least some sense. That or I am becoming known for being a local activist and thorn in the side of other engineers trying and sometimes failing to do a good job...

[dallardice]

The first point you make is about the overhead gantry on the eastbound M4 just before J19 suggests and you feel contradicts the yellow temporary signs. Your suggestion to cover the gantry sign is a very valid one, but unfortunately, we are unable to do this. We are limited to what we can and can’t do with the existing overhead gantry signage, as such, we’ve had to reach a compromise between practicality and safety. In terms of the lanes, there are two lanes which can exit for the M32 from the M4 eastbound, both access this slip road.
They never really explained why they can't properly cover the signs. Perhaps some of our temporary works experts might understand the rules here a bit better. Also, to be fair, covering the signs may not entirely work as 'locals' and regulars might still assume that LBS1 and LBS2 both exit with the M32 leaving one mainline lane.

A very simple thing I think they could do there would be to move the yellow temporary signs to before the gantry. If I remember rightly, there are two gantries showing the single lane for the M4 before either of the yellow temporary signs. On the westbound, the temporary signs are before the amended gantries.

[DB617]

The first point you make is about the overhead gantry on the eastbound M4 just before J19 suggests and you feel contradicts the yellow temporary signs. Your suggestion to cover the gantry sign is a very valid one, but unfortunately, we are unable to do this. We are limited to what we can and can’t do with the existing overhead gantry signage, as such, we’ve had to reach a compromise between practicality and safety. In terms of the lanes, there are two lanes which can exit for the M32 from the M4 eastbound, both access this slip road.
They never really explained why they can't properly cover the signs. Perhaps some of our temporary works experts might understand the rules here a bit better. Also, to be fair, covering the signs may not entirely work as 'locals' and regulars might still assume that LBS1 and LBS2 both exit with the M32 leaving one mainline lane.

A very simple thing I think they could do there would be to move the yellow temporary signs to before the gantry. If I remember rightly, there are two gantries showing the single lane for the M4 before either of the yellow temporary signs. On the westbound, the temporary signs are before the amended gantries.

Even an early set of signs would suffice. The cost of the signs would be negligible compared to that of the whole scheme TM. One wonders if the people who design these schemes actually drive, because all it takes is one person to get the sign blocked by an HGV and flow breakdown occurs when they panic.

[DB617]

As if by magic, I arrive at J19 today to find an IPV indicating 'move right' and a NHTO car recovering a blown up old car, and lo and behold (though I acknowledge it is now the school holidays) the traffic through the junction was totally smooth despite the disruption.

It's almost as if I was talking sense...

[dallardice]

Signs at these works seem to have been amended to show "Completion Summer 2024" - I had thought that the original plan was to complete by the end of this year.

[DB617]

Signs at these works seem to have been amended to show "Completion Summer 2024" - I had thought that the original plan was to complete by the end of this year.

Yes, I noticed too, I haven't bothered them again to clarify but it could be delays to the barrier scheme or equally, they could be keeping restrictions on the M4 due to the refurbishment of the interchange bridges which was indeed programmed to finish mid-24.

It needs to, as well, because otherwise the yearly migration from Birmingham to Cornwall is going to be utter carnage...

[DB617]

The M4 seems to be on schedule for completion by 'Summer 2024'. Last week I noticed the WB hard temporary barriers had come out, replaced by cones, I guess that means there won't be any more personnel or machinery in that carriageway from now on. There is still some spoil piled up near the M32 junction.

Next question really is whether the WB smart motorway is Iikely to be handed back over any time soon. It doesn't look like there's much need for the lane closure anymore, unless there is something going on at the Almondsbury end as I always exit towards the M5 SB.

It was quite remarkable how quickly the concrete barrier was cast, considering it rained for most of the winter and most of us know that can be havoc for sensitive concrete jobs. Then the lighting columns seemed to go up in a fortnight. Not bad. The drainage works appeared to take up over two-thirds of the scheme duration.

Edit: Headed WB today after work. All TM gone, back to NSL but no sign of hard shoulder running.

[AAndy]

Video heading East https://youtu.be/hBdI02iGK6c?si=aY6xIpvrHfmZ3FR8