New M5 Junction 10 Planned

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Bryn666
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Re: New M5 Junction 10 Planned

Post by Bryn666 »

booshank wrote: Fri Oct 16, 2020 15:18 Hasn't this been going on for many decades now, this "not invented here" attitude? For example the USA had already developed quite a bit of experience with freeways (and regional equivalents) when Britain started building its first motorways, such as the first part of the Hollywood Freeway opening in 1940. Yet rather than learning from and developing that experience, it seems Britain decided to reinvent the wheel, maybe even inventing entirely new terms. Not everything they came up with was bad or inferior of course, but it seems that a big opportunity to build on existing experience was missed. Other countries obviously took that experience on board and adapted it to local conditions, making improvements or compromises based on budget/space/traffic volumes etc.
James Drake visited both Germany (Organisation Todt hosted him and several other highway planners in 1938) and the USA after the war where he experienced the PA Turnpike (opened in 1940), which was America's first true intercity route. The influences were there for him, and he took on board the best bits. Other counties didn't seem to get the memo so whilst Lancashire pressed ahead with plans for a D3M motorway across the county with elegant interchange design, Worcestershire designed the M5 as if it was a 1930s autobahn (down to the straight sections and sharp curves) with single carriageway slip roads at most of its interchanges. Kent went ahead and did similar with the M2 and A20(M).

The exception was the M1, which was designed more akin to an Italian autostrade, ignore the hills, just go in a straight line over each one.

Motorway design wasn't really codified into a single national document until the mid 1970s - and that's where it's stubbornly remained since.
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Re: New M5 Junction 10 Planned

Post by Isleworth1961 »

Ross Spur wrote: Fri Oct 16, 2020 10:43 Opening Dates were:

J8 - J10 Strensham Interchange to Piffs Elm : 16 June 1970
J10 - J13 Piffs Elm to Stroudwater : 6 April 1971
J13 - J15 Stroudwater to Almondsbury Interchange : 3 December 1971. Also included the 1 mile through the interchange.
Thank you for those dates.
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Re: New M5 Junction 10 Planned

Post by Peter Freeman »

booshank wrote: Fri Oct 16, 2020 15:18 Hasn't this been going on for many decades now, this "not invented here" attitude?
Yes, it has. Another example is the nuclear power industry, in which I worked in the 1970's.

In 1953 the UK began building the world's first nuclear power station at Calder Hall (now Sellafield). The reactor was gas-cooled. Meanwhile, in 1955 the USA commissioned USS Nautilus, the world's first nuclear submarine, using a smaller and simpler reactor that was water-cooled: a pressurised water reactor, PWR. Soon they began to build commercial land-based power stations, overtaking us. Their first, in 1957, was at Shippingport, and used a submarine reactor plonked on land. Americans continued their successful commercial industry with PWR's (and some BWR's, a minor variant).

The UK built its first nuclear submarine, HMS Dreadnought, in 1960 with a PWR copied exactly from the USA's. Subsequently we designed our own (but USA-copy) submarine PWRs, and have, sensibly, used them ever since. However, on land we persisted with gas cooling - first Magnox types then AGRs. We were virtually the only country to do so: PWRs reigned everywhere else. We thought ours were more 'elegant', but others in the game were pragmatic. Of course we, and others, experimented with advanced concepts such as molten salt cooling, fast breeders, heavy water cooling/moderation, etc (all dead-ends), but essentially it was: UK gas-cooled, rest of the world water-cooled. 'Not invented here'.

Eventually, after decades, the UK relented, bowing to the obvious, but it was too late as the (terrestrial) nuclear power industry has no future. Perhaps eventually the UK will adopt the clearly-superior SPDIs and DDIs instead of roundabouts, but too late as UK motorway building is almost over.
Last edited by Peter Freeman on Mon Oct 19, 2020 00:26, edited 1 time in total.
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Re: New M5 Junction 10 Planned

Post by Peter Freeman »

Bryn666 wrote: Fri Oct 16, 2020 14:26 Every walk of life in government circles at the moment seems to disregard international best practice or convention.
eg. UK reaction (lack of) to covid19.
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Re: New M5 Junction 10 Planned

Post by ABB125 »

Preferred Route Announcement (PRA):
https://www.gloucestershire.gov.uk/medi ... eaflet.pdf

There's also a full consultation report and another document available in the grey box at the top of the page:
https://www.gloucestershire.gov.uk/high ... ts-scheme/

In summary:
  • Unsurprisingly (given that there were no other options) the new M5 junction will be a two-bridge roundabout. The PRA document does mention that a few alternative ideas were suggested, and these were considered and can be found in the consultation report. I haven't read that yet; I wonder what they thought of my suggestion? :D
  • Bizarrely, the most popular option was Option 2, the one where the new roundabout is centred on the existing bridge (ie: the current bridge is demolished, and two new ones built). Quite why the northern offset option wasn't the most popular I'm not sure, especially as it would likely involve less demolition and was cheaper (admittedly it was the second-most popular option).
  • The new link road paralleling the M5 has been downgraded to single carriageway, because apparently the predicted traffic flows are within the guidelines for S2.
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Re: New M5 Junction 10 Planned

Post by Peter Freeman »

An exciting options brochure! Henry Ford (black cars) would have loved it.
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Re: New M5 Junction 10 Planned

Post by jackal »

The consultants apparently can't comprehend the words 'free-flow':
Can a lilo junction using the existing
loop be provided? A similar
arrangement could be built in the
opposite quadrant. A dumbbell
roundabout arrangement with free-flow
filter lanes for Cheltenham to the north
and from the north to Cheltenham could
be used.
[Reply]A dumb-bell roundabout junction (lilo junction) would not meet the forecast
traffic flow requirements. This was previously investigated and rejected as
an option.
(From the consultation report.)
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Bryn666
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Re: New M5 Junction 10 Planned

Post by Bryn666 »

jackal wrote: Wed Jun 16, 2021 16:27 The consultants apparently can't comprehend the words 'free-flow':
Can a lilo junction using the existing
loop be provided? A similar
arrangement could be built in the
opposite quadrant. A dumbbell
roundabout arrangement with free-flow
filter lanes for Cheltenham to the north
and from the north to Cheltenham could
be used.
[Reply]A dumb-bell roundabout junction (lilo junction) would not meet the forecast
traffic flow requirements. This was previously investigated and rejected as
an option.
(From the consultation report.)
Or LILO...
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ABB125
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Re: New M5 Junction 10 Planned

Post by ABB125 »

jackal wrote: Wed Jun 16, 2021 16:27 The consultants apparently can't comprehend the words 'free-flow':
Can a lilo junction using the existing
loop be provided? A similar
arrangement could be built in the
opposite quadrant. A dumbbell
roundabout arrangement with free-flow
filter lanes for Cheltenham to the north
and from the north to Cheltenham could
be used.
[Reply]A dumb-bell roundabout junction (lilo junction) would not meet the forecast
traffic flow requirements. This was previously investigated and rejected as
an option.
(From the consultation report.)
I think that's actually the response I submitted! I'm pretty sure I capitalised LILO though...
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Re: New M5 Junction 10 Planned

Post by ABB125 »

I've finally found time to look at the statutory consultation information for J10. The scheme page can be found here: https://www.gloucestershire.gov.uk/high ... ts-scheme/

Detailed(ish) plans are here: https://www.gloucestershire.gov.uk/medi ... 150222.pdf

In summary:
  • The new M5 roundabout will be fully signalised (I'm shocked! Not :roll: ). 3 lanes on both bridges across the M5, 4 lanes to the west, 2 to the east.
  • The proposed smaller roundabout to the east of the M5 has been changed to a signalised crossroads. I'm ambivalent about this (but see my concerns later).
  • The scheme now includes dualling of the whole of the A4019 as far as the existing dualled section into Cheltenham, instead of leaving a short section to be dualled as part of a retail development (or something like that). Very sensible, in my opinion, to combine this into one scheme.
  • The "upgrade" of Coombe Hill junction on the A38 has been removed from the J10 scheme, to allow it to be delivered quicker (I'll believe it when I see it!), though I believe this was announced previously in the Preferred Route Announcement.
  • Also previously announced, the new "West Cheltenham Link Road (or whatever it's called) will be a single carriageway instead of dual.
  • Interestingly, between the new roundabout and crossroads, heading away from Cheltenham there will be 3 lanes, but heading towards Cheltenham there'll only be 2. Does this indicate that the signalised roundabout will be causing more queueing than the crossroads, thus needing more stacking space?
I have a major concern with these plans. The plans of the new signalised crossroads show the northern arm being rather more substantial than the southern arm. Yet, as far as I'm aware there are no firm plans for development north of the A4019 here. (Obviously there are plans for development here, but I don't think they're at the "how little can we get away with in terms of road provision" stage yet.) Thus, I'm worried that this will be the starting point for the planned Ashchurch bypass (and diversion of the A46); yet a fully-signalised roundabout and crossroad double-whammy is hardly the ideal starting point for a short section of "expressway". Adding to my suspicions (ignoring the fact that the Councillor in charge of Highways at Gloucestershire County Council has publicly stated that his personally preferred route for the Ashchurch bypass starts at J10) is that the off-slip from the M5 on the northbound side is more substantial than the southbound off-slip; yet the more popular turning movement at this junction should be people heading into Cheltenham from the north (as served by the current J10; arrivals into Cheltenham from the south will be better served by J11). The only part of the plans which suggest I'm wrong is the fact that the crossroads seems geared up for northern arm to/from Cheltenham as the biggest flow (since it is served by dedicated 2-lane filters), rather than to/from the M5.
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Re: New M5 Junction 10 Planned

Post by Mapper89062 »

ABB125 wrote: Sun Dec 26, 2021 20:45
  • The proposed smaller roundabout to the east of the M5 has been changed to a signalised crossroads. I'm ambivalent about this (but see my concerns later).

    I have a major concern with these plans. The plans of the new signalised crossroads show the northern arm being rather more substantial than the southern arm. Yet, as far as I'm aware there are no firm plans for development north of the A4019 here. (Obviously there are plans for development here, but I don't think they're at the "how little can we get away with in terms of road provision" stage yet.) Thus, I'm worried that this will be the starting point for the planned Ashchurch bypass (and diversion of the A46); yet a fully-signalised roundabout and crossroad double-whammy is hardly the ideal starting point for a short section of "expressway". Adding to my suspicions (ignoring the fact that the Councillor in charge of Highways at Gloucestershire County Council has publicly stated that his personally preferred route for the Ashchurch bypass starts at J10) is that the off-slip from the M5 on the northbound side is more substantial than the southbound off-slip; yet the more popular turning movement at this junction should be people heading into Cheltenham from the north (as served by the current J10; arrivals into Cheltenham from the south will be better served by J11). The only part of the plans which suggest I'm wrong is the fact that the crossroads seems geared up for northern arm to/from Cheltenham as the biggest flow (since it is served by dedicated 2-lane filters), rather than to/from the M5.
I think a signalised crossroads might be better there since the rest of the junctions along the route are signalised, allowing for better synchronisation between the junctions.

In addition to the two-lane filter for north arm -> Cheltenham that you mention, Cheltenham -> north arm gets two lanes while the left turn from the motorway to the north arm only has one, which seems particularly strange if this is the start of a short bit of expressway heading to the A46. So my guess is either that high-capacity stub is intended for a more substantial development link road that will have a big flow towards the town centre (perhaps a big development north of Cheltenham is planned long-term, and they want a link from it to the motorway, maybe continuing towards Bishop's Cleeve?) or they want to combine some local development route heading that way with a watered-down Ashchurch bypass (which is obviously disastrous news.) The south-facing movements at junction 10 could either be related to that, or maybe they simply expect that with all the new development planned those movements will become dominant.
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Re: New M5 Junction 10 Planned

Post by Micro The Maniac »

Mapper89062 wrote: Sun Dec 26, 2021 21:53 I think a signalised crossroads might be better there since the rest of the junctions along the route are signalised, allowing for better synchronisation between the junctions.
Synchronisation of lights between the junctions? You must be new to UK roads :D

The one thing we can be sure of... that the one thing the lights will not be is correctly synchronised.
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Re: New M5 Junction 10 Planned

Post by M19 »

Why does the M5 roundabout have those horrible entry angles onto the roundabout and reverse curves between the roundabout entries and exits?

Drivers will not follow that curvature and use the full width of the road, but that creates a problem of entry path overlap and sideswipe accidents. Why are we fixated on road layouts that promotes traffic path conflicts?

J27 of the M5 is an example where there are no reverse curves. Should be like that geometry wise.
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Re: New M5 Junction 10 Planned

Post by ABB125 »

M19 wrote: Mon Dec 27, 2021 15:45 Why does the M5 roundabout have those horrible entry angles onto the roundabout and reverse curves between the roundabout entries and exits?

Drivers will not follow that curvature and use the full width of the road, but that creates a problem of entry path overlap and sideswipe accidents. Why are we fixated on road layouts that promotes traffic path conflicts?

J27 of the M5 is an example where there are no reverse curves. Should be like that geometry wise.
No idea! Maybe it's "safer" (based on some useless data)?

One that I've used quite a lot recently with this problem is this: https://www.google.com/maps/@52.3738707 ... a=!3m1!1e3
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Re: New M5 Junction 10 Planned

Post by Phil »

ABB125 wrote: Mon Dec 27, 2021 18:55
M19 wrote: Mon Dec 27, 2021 15:45 Why does the M5 roundabout have those horrible entry angles onto the roundabout and reverse curves between the roundabout entries and exits?

Drivers will not follow that curvature and use the full width of the road, but that creates a problem of entry path overlap and sideswipe accidents. Why are we fixated on road layouts that promotes traffic path conflicts?

J27 of the M5 is an example where there are no reverse curves. Should be like that geometry wise.
No idea! Maybe it's "safer" (based on some useless data)?

One that I've used quite a lot recently with this problem is this: https://www.google.com/maps/@52.3738707 ... a=!3m1!1e3
IIRC the idea is that drivers 'have' to slow down to stay within the lane markings thus reducing the possibility of highish speed collisions while entering the roundabout.

Of course in reality drivers will chose the past of least resistance as it were - but that sort of thing is deemed irrelevant by the pen pushers in Whitehall who can loudly trumpet how they have made the design codes 'safer'
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Re: New M5 Junction 10 Planned

Post by Truvelo »

Phil wrote: Tue Dec 28, 2021 15:36
ABB125 wrote: Mon Dec 27, 2021 18:55
M19 wrote: Mon Dec 27, 2021 15:45 Why does the M5 roundabout have those horrible entry angles onto the roundabout and reverse curves between the roundabout entries and exits?

Drivers will not follow that curvature and use the full width of the road, but that creates a problem of entry path overlap and sideswipe accidents. Why are we fixated on road layouts that promotes traffic path conflicts?

J27 of the M5 is an example where there are no reverse curves. Should be like that geometry wise.
No idea! Maybe it's "safer" (based on some useless data)?

One that I've used quite a lot recently with this problem is this: https://www.google.com/maps/@52.3738707 ... a=!3m1!1e3
IIRC the idea is that drivers 'have' to slow down to stay within the lane markings thus reducing the possibility of highish speed collisions while entering the roundabout.

Of course in reality drivers will chose the past of least resistance as it were - but that sort of thing is deemed irrelevant by the pen pushers in Whitehall who can loudly trumpet how they have made the design codes 'safer'
Both the A4019 approaches onto the roundabout caught my eye when first seeing the drawings. As the roundabout will be signalised there is no excuse for such sharp entry angles. If anything it could achieve the exact opposite when drivers see an amber light and hit the gas to get through before it turns red. The sharp geometry could cause a loss of control in such circumstances.
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Re: New M5 Junction 10 Planned

Post by chaseracer »

ABB125 wrote: Mon Dec 27, 2021 18:55 One that I've used quite a lot recently with this problem is this: https://www.google.com/maps/@52.3738707 ... a=!3m1!1e3
Yes, that's often fun* when it's busy.
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Re: New M5 Junction 10 Planned

Post by Big L »

chaseracer wrote: Wed Dec 29, 2021 15:41
ABB125 wrote: Mon Dec 27, 2021 18:55 One that I've used quite a lot recently with this problem is this: https://www.google.com/maps/@52.3738707 ... a=!3m1!1e3
Yes, that's often fun* when it's busy.
Worth using it to get to Becketts.
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Re: New M5 Junction 10 Planned

Post by jackal »

ABB125 wrote: Sun Dec 26, 2021 20:45 I have a major concern with these plans. The plans of the new signalised crossroads show the northern arm being rather more substantial than the southern arm. Yet, as far as I'm aware there are no firm plans for development north of the A4019 here. (Obviously there are plans for development here, but I don't think they're at the "how little can we get away with in terms of road provision" stage yet.) Thus, I'm worried that this will be the starting point for the planned Ashchurch bypass (and diversion of the A46); yet a fully-signalised roundabout and crossroad double-whammy is hardly the ideal starting point for a short section of "expressway". Adding to my suspicions (ignoring the fact that the Councillor in charge of Highways at Gloucestershire County Council has publicly stated that his personally preferred route for the Ashchurch bypass starts at J10) is that the off-slip from the M5 on the northbound side is more substantial than the southbound off-slip; yet the more popular turning movement at this junction should be people heading into Cheltenham from the north (as served by the current J10; arrivals into Cheltenham from the south will be better served by J11). The only part of the plans which suggest I'm wrong is the fact that the crossroads seems geared up for northern arm to/from Cheltenham as the biggest flow (since it is served by dedicated 2-lane filters), rather than to/from the M5.
I take it this is the Councillor Smith that authored the absurd 'business case':
 Favoured by many local communities the A46 route for a dual track trunk road from
Teddington Hands to the new 4 way M5 junction 10
o Hamburg roundabout to the west of existing roundabout at Teddington Hands
 Retain access to local amenities.
 Reduced noise, air and light pollution for Teddington.
o Route across open farm land giving improved access for
 Bishops Cleeve
 Gloucestershire’s premier events location Cheltenham Race course
 Proposed Cyber Hub in Cheltenham
 Integrating with the proposed development and road improvements to the
West of Cheltenham.
 Reduction in traffic on the A435 giving safer access for villages.
 Cost advantages
o The route may be longer than some possible alternatives (3-4 miles) which could
cost in the region £25 million extra to build, however it would not require to build
another motorway roundabout making a saving of £250 Million.
o Less disruption on the motorway due to not having to build a new motorway
junction.
Where to start with such nonsense?

- 'Dual track'?
- 'Hamburg roundabout'?
- 'Route across open farm land' being an advantage?
- 3-4 miles of extra DC costs £25m? Nevermind that in reality it's £100m-£200m.
- A simple GSJ costs £250m? ~£50m in the real world.
- And of course there are no congestion implications from casually throwing J9 traffic onto the planned J10 roundabout :roll:

I absolutely agree it's a big problem with the J10 design that it panders to such delusions. As noted elsewhere, sending the A46 to J10 is drastically outperformed by the more sensible approach of a freeflow junction south of J9: viewtopic.php?f=1&t=41295

PS: The J10 consultation website is here: https://m5-junction-10-have-your-say.gl ... /#/EN/home
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Re: New M5 Junction 10 Planned

Post by JammyDodge »

I like everything but the design of J10. It is truly dog-crap
I have attempted to describe a design along the lines of this in my consultation response, which I believe would be better:
Screenshot 2021-12-29 201119.jpg
Designing Tomorrow, Around the Past
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