New M5 Junction 10 Planned

[ForestChav]

If this is going to basically be a further bit of re-routing the A46 into Cheltenham then surely the sensible thing is to try and make the flows on and off the M5 northbound into Cheltenham as easy as possible. (Renumbering it as A46 would make some sense at least since at present without knowing the history it doesn't make a lot of sense with the A46 suddenly disappearing in the middle of Cheltenham and then reappearing at J9).

So it would be logical to have this junction full access even though ironically the two movements you'd need to make the A46 designation logical are the ones which are already there. But certainly it would be tricky to keep the free flow onto the M5 without flattening what's already there especially since there's already going to be a roundabout in there. The left turn off the M5 would of course be much easier to do.

I have to admit I'm not the greatest fan of signals on roundabouts either but it is common on larger ones because of the traffic volumes, at least part time. Free-flow with the all purpose roads is clearly going to be tricky here as most traffic will be turning - I can't imagine a lot will be carrying on to the A38 given that you are probably quicker going on the M5 and off at J9 for Tewkesbury.

I could understand why they transferred the A46 from its original route across the Cotswolds (now B4632) onto the A422-A435 alignment, but I was never convinced that having it take over the first part of the A438 and meet the M5 (which is the poorest quality stretch of the whole route between the M5 and M6/M69) was necessarily a good idea. The A46 is white-signed from Cheltenham to the A433, and while it is lovely drive - and highly recommended to anybody who hasn't driven it! - there is no particular reason why it needed to retain the A46 number. If it was going to retain the number, then why not route the A46 down the A435 into Cheltenham rather than along the A438 to the M5?

Considering what has been done, though, your suggestion of having the A46 take over the end of A4019 from the M5 into Cheltenham makes good sense.

Well it wasn't 100% my idea, just with the other mentions of the improvements further north on the A46, that one option here could be to at least have it run down the A4019 (which is a more inconsequential number) than just disappear out of nowhere because the B4632 was never up to it and they never finished renumbering the alternative) - in terms of following the route all you'd need to do then is follow up the A38 into Tewkesbury or the M5 for a junction plus it looks like there's another important route into Cheltenham not just the A40.

[Chris5156]

I don't think a six ramp parclo appears in the DMRB so naturally it has to be shunned as foreign muck. Much better to have British superiority in the form of a crap roundabout alignment which will cause entry parth conflicts controlled by signals as "mitigation".

However in the real world, there are usually a whole raft of junction options produced that are sifted on cost feasibility etc basis to see the best performers that are then worked up to options to be studied in detail. It may well be that this option was considered in the initial stages.
When consulting on a the chosen option for a preferred route, any alternatives proposed by the public would also be worked up to a similar level of detail to see how they performed relative to the proposed preferred route. In the case of the one I was involved with (M1J13), the alternative arrangement proposed by a then member of this forum was worked up to quite a reasonable level of detail and it could be seen that against (IIRC) journey time, environmental effects, land and construction cost it performed less well than the preferred route, so was not pursued any further.
The same would be true of any alternative proposed at the consultation stage - it would be worked up and appraised and probably be mentioned in the Inspector's/Examination report.
If the sketch above was only proposed recently then it is probably too late, and unfortunately cannot be considered without setting the project back several years.

You'll of course know that early sifting is usually very perfunctory. The fact that DMRB says a parclo is a low capacity design similar to a diamond would be quite enough to banish the concept, and move on to the real business of choosing between a dumbbell or a 2 bridge rbt, the designs that everyone in the room would be comfortable with and expecting, regardless of their lack of capacity compared to non-DMRB designs like the 6 ramp parclo, SPUI or DDI.

The paper trail is incomplete, but certainly something like a parclo seems to have been considered at an early stage.

The Scoping Report submitted to the Planning Inspectorate in July 2021 includes a section on options sifting (p28).

It says that JMP Consulting produced a report in July 2012 - which appears not to be available anywhere online - that proposed four options to convert J10 to an all movements junction. The scoping report says:

All options proposed to keep the existing northbound entry slip loop and avoid any impact on the commercial properties in the north west quadrant. They also sought to minimise the impacts on the residential properties on Withybridge Gardens. Because of this, all four options included at least one signalised slip road junction with the A4019.

That sounds like conversion to something like a parclo, but that written description is all I can find.

The next study was carried out by Aecom in 2018 which the report says "identified several options" but doesn't bother describing them at all. The report is not online.

Following that, Amey were brought in. Their July 2018 report had several proposals. Again, it's not online, but is described in the scoping report:

These included various arrangements of a full movement Junction 10 located south, at, and north of the existing junction. A comparison of the options led to the development of three Concept Options included in the Homes England Business Case.

From the six 2018 options, three were then developed further by Amey in 2019, resulting in these:

• Concept Option 1 – Junction 10 moved north of its existing location;
• Concept Option 2 – Upgrade to the existing Junction 10; and
• Concept Option 3 – Junction 10 moved south of its existing location, including a
direct link to the B4634.

Reading on, it becomes apparent that all three are two-bridge roundabout junctions. A further "workshop" then expanded this list out again, but only to tinker with the location and alignment of the roundabout, and introduce a variant of option 2 that was a dumbbell junction, which was quickly rejected anyway.

So as far as options sifting goes, some sort of parclo variant was in the running back when the project started in 2012, but disappeared without any reason being given. It looks rather like everything JMP Consulting and Aecom did on this project was abandoned when Amey came on board, since there is no hint that any of Amey's six options were in any way related to the work that had gone before. Amey's work only appears to have considered a two-bridge roundabout, and their variations were simply about where it would be located and whether the existing junction bridge would be re-used or not. The public consultation, when it started, was therefore simply a question of whether to build a two-bridge roundabout on the site of the current junction, or a bit north of it, or a bit further north of that, or a bit further north of that.

In other words, I can't find any evidence that any design that wasn't a two-bridge roundabout was given serious consideration, and as soon as that layout was suggested, nothing else got a look-in. It does not look like anything else was ever in the running. The 2020 consultation did not, as far as I can tell, result in any other designs being suggested by the public - or if any were, they were not considered important enough to even be mentioned in the report. But I really don't think it should take suggestions from the public to get the consultants and council to evaluate more than one junction type when designing a £200m project.

I would really like to see the reports produced by JMP, Aecom and Amey, but none are online so the process has hardly been transparent.

[jackal]

Thanks for that, Chris. I've also previously mentioned this from the consultation report:

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.

[ABB125]

Thanks for that, Chris. I've also previously mentioned this from the consultation report:

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.

Ah yes, my submission to the consultation! I could perhaps have worded it slightly better: "they" probably saw the word "dumbbell" and thus "insert standard 'you haven't got a clue what you're on about' fob-off excuse here".

[jackal]

This has been accepted for examination by PINS. The layout is much as before - a signalised two-bridge roundabout with no freeflow, plus a short link road and localised widening. The funding statement indicates an eye-watering £293m pricetag.

PINS page: https://national-infrastructure-consent ... s/TR010063
General arrangement part 1: https://infrastructure.planninginspecto ... plans1.pdf
Part 2: https://infrastructure.planninginspecto ... plans2.pdf

[Bryn666]

This has been accepted for examination by PINS. The layout is much as before - a signalised two-bridge roundabout with no freeflow, plus a short link road and localised widening. The funding statement indicates an eye-watering £293m pricetag.

PINS page: https://national-infrastructure-consent ... s/TR010063
General arrangement part 1: https://infrastructure.planninginspecto ... plans1.pdf
Part 2: https://infrastructure.planninginspecto ... plans2.pdf

I'm hoping that near £300m covers the dualling works and associated link roads away from J10 as well, otherwise the question really has to be asked why two bridges cost nearly a third of a billion.

[Chris Bertram]

They have the audacity to call it an "Improvement"?

[Herned]

I'm hoping that near £300m covers the dualling works and associated link roads away from J10 as well, otherwise the question really has to be asked why two bridges cost nearly a third of a billion.

Given the fairly similar scheme on the A249 is costing £40m, it does seem a little pricey, to put it mildly

[AnOrdinarySABREUser]

I'm hoping that near £300m covers the dualling works and associated link roads away from J10 as well, otherwise the question really has to be asked why two bridges cost nearly a third of a billion.

Given the fairly similar scheme on the A249 is costing £40m, it does seem a little pricey, to put it mildly

£92mn - not £40mn - has been allocated to improve M2 J5, but the price of this scheme is still 307% greater than that of M2 J5 for an outright downgrade!!!

The benefits of full access at M5 J10 are completely diminished by the removal of the freeflowing turns at the moment, which I presume caters to a majority of demand in the area. Jackal's sketch should've been the option they selected in my opinion, though I have zero qualifications so I can't provide full comment here, but to me it seems to be the most reasonable proposal presented.

Are traffic engineers in the UK that severely restricted by the DMRB or do they willingly narrow their vision to what the DMRB says verbatim? I know that there may be ulterior motives to the improvement but it does seem bizarre given that there is plenty of land to the east of the junction to develop where a junction can be provided for future development.

Once again, hundreds of millions of pounds go down the drain with hundreds of tons of CO2 emitted as a result.

Can't wait to see the £13bn to be spent on the LTC only for it to be gridlocked within a year or two.

[Big L]

They have the audacity to call it an "Improvement"?

Half a junction to a full junction sounds like an improvement.

[AnOrdinarySABREUser]

They have the audacity to call it an "Improvement"?

Half a junction to a full junction sounds like an improvement.

A full access junction is good, but when you're making the pre-existing freeflow movements which cater for a majority of demand in the area at-grade, then you're worsening traffic flow, so the overall improvement is very low.

[RichardA35]

They have the audacity to call it an "Improvement"?

Half a junction to a full junction sounds like an improvement.

A full access junction is good, but when you're making the pre-existing freeflow movements which cater for a majority of demand in the area at-grade, then you're worsening traffic flow, so the overall improvement is very low.

A read of document 7.5 Appendix L will give you an insight into the traffic forecasting that is carried out for a scheme of this type. There is forecast to be a lot of development in the area and the scenario of doing nothing suggests increasing congestion along the M5. The scheme is proposed to deal with the additional traffic generated by the developments and distribute it onto its destination via the motorway network. It may well be that the "majority of demand" is altered following changes in trip generation from the proposed developments in the area and this will be seen over an approx. 15 year timescale as the developments are constructed and occupied.

[Truvelo]

Look what happened when the nearby J12 was made full access by removing the freeflow. The queue backed up onto the M5 and the slip road had to be extended by losing some of the hard shoulder. Traffic lights were soon installed to deal with the problem. Thing is, the original proposal was to incorporate the freeflow into the scheme but they said the bridge was kaput.

[Bryn666]

Traffic forecasting is of course only as good as the inputted data. No developer is ever going to admit their project will make things worse so they always manage to find ways to make it look like everything is fine.

Making J10 full access will of course unleash a lot of new journey potential and this suppressed demand factor combined with induced from new developments will probably make this another junction that becomes a headache in a few years.

[Herned]

£92mn - not £40mn - has been allocated to improve M2 J5, but the price of this scheme is still 307% greater than that of M2 J5 for an outright downgrade!!!

I was thinking of the junction near Sittingbourne, but M2 J5 is a decent comparator too. The costs of this plan are lunacy

[AnOrdinarySABREUser]

£92mn - not £40mn - has been allocated to improve M2 J5, but the price of this scheme is still 307% greater than that of M2 J5 for an outright downgrade!!!

I was thinking of the junction near Sittingbourne, but M2 J5 is a decent comparator too. The costs of this plan are lunacy

Grovehurst? That’s another unfortunate scheme, though it doesn’t cost nearly as much. Other members have pointed out that the extra cost for M5 J10 could account for the dualling, though it does seem extortionate for such a small stretch of dual carriageway.