A428 Black Cat - Caxton Gibbet improvement

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bazzapurple
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A428 Black Cat - Caxton Gibbet improvement

Post by bazzapurple »

Evening all.
I've heard second hand, that residents in the St Neots area have been sent letters, informing them that some surveys will be going on.
The reason given is that they're looking into a new road from Black Cat to Cambourne.
Just wondering if anyone has anything on this???
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KeithW
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Re: Black Cat - Cambourne rumour?

Post by KeithW »

This is a route that has been talked about for years. I will believe it when I see it.
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c2R
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Re: Black Cat - Cambourne rumour?

Post by c2R »

Only thatn it was a part of the last roads programme announcement, that Oxford to Cambridge was a "growth route". I can't see much happening for a while on this route, althouth the Black Cat to Caxton Gibbet is probably the next piece in the puzzle that is likely to be widened...
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jackal
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Re: Black Cat - Cambourne rumour?

Post by jackal »

It's more than a rumour - A428 Black Cat to Caxton Gibbet is committed for this road period (i.e. 2015-20 - see here, Part 2, p. 43). This means funding has been allocated to start construction by the end of 2019/20, so I'm expecting a big announcement soon. Probably the preparations for this are what OP is talking about.

There is a separate Oxford to Cambridge Expressway study, which is considering the whole corridor. Anything that comes out of this, such as options for filling the gap between the M1 and M40, will be much further down the line - it is intended only to inform the next RIS (i.e. for post-2020 improvements).
Last edited by jackal on Tue May 03, 2016 09:41, edited 1 time in total.
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Chris5156
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Re: Black Cat - Cambourne rumour?

Post by Chris5156 »

jackal wrote:It's more than a rumour - A428 Black Cat to Caxton Gibbet is committed for this road period (i.e. 2015-20 - see here, p. 43). This means funding has been allocated to start construction by the end of 2019/20, so I'm expecting a big announcement soon. Probably the preparations for this are what OP is talking about.
That's interesting - this scheme effectively didn't exist before, and it's now being accelerated past lots of other things that have been patiently plodding through the planning process for years.

When is the A1 Baldock-Alconbury study supposed to report back? I'd have thought that the results of that study would need to inform the design of this scheme. (If it helps speed things up, I am happy to let Highways England borrow my copy of the early 1990s plans for the A1(M) Baldock-Alconbury scheme so they can copy it.)
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Re: Black Cat - Cambourne rumour?

Post by Haydn1971 »

Yes, it's a new dual carriageway from Black Cat, which iirc passes south of Little Barford, then rejoins the A428 alignment - black cat becomes a dumb bell type junction in the most recent plan I saw - essentially fills the dual carriageway gap
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Re: Black Cat - Cambourne rumour?

Post by roadtester »

Chris5156 wrote:When is the A1 Baldock-Alconbury study supposed to report back? I'd have thought that the results of that study would need to inform the design of this scheme. (If it helps speed things up, I am happy to let Highways England borrow my copy of the early 1990s plans for the A1(M) Baldock-Alconbury scheme so they can copy it.)
Yes, surely knowing at the very least knowing whether any A1 changes there will be on-line or off-line will make a big difference.

That said, I hope they get cracking. As anyone who is familiar with this area on the ground it's a gap that's screaming to be filled (cue several people saying there are loads of other places with higher traffic flows - yes, I know!).

If they accelerate both Black Cat to Caxton Gibbet and a local A1 upgrade, even better.
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Re: Black Cat - Cambourne rumour?

Post by roadtester »

Haydn1971 wrote:Yes, it's a new dual carriageway from Black Cat, which iirc passes south of Little Barford, then rejoins the A428 alignment - black cat becomes a dumb bell type junction in the most recent plan I saw - essentially fills the dual carriageway gap
Just trying to visualise that - is the A421-428 free flow throughout or is it interrupted at grade?
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jackal
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Re: Black Cat - Cambourne rumour?

Post by jackal »

Chris5156 wrote:
jackal wrote:It's more than a rumour - A428 Black Cat to Caxton Gibbet is committed for this road period (i.e. 2015-20 - see here, p. 43). This means funding has been allocated to start construction by the end of 2019/20, so I'm expecting a big announcement soon. Probably the preparations for this are what OP is talking about.
That's interesting - this scheme effectively didn't exist before, and it's now being accelerated past lots of other things that have been patiently plodding through the planning process for years.
I suppose it has the benefit of being on the suddenly fashionable Oxford-Cambridge expressway corridor. Though it should also be said that some of the schemes you are talking about are probably at a similarly advanced stage but like the A428 scheme have gone largely under the radar thus far. There are a lot of committed schemes in the RIS that must be breaking cover soon. I've noticed about five coming up just in the last few weeks - I've posted about some, other ones like the A500 widening I couldn't be bothered with :)
When is the A1 Baldock-Alconbury study supposed to report back?
October 2016. Details here. But even when that's done we will be years away from a 'preferred option'. In fact there is no commitment to any improvement for the A1 either side of Black Cat (other than side effects of the A428 upgrade)

From what Haydn says I guess the plan is just to build the A428 route with a 'bare minimum' GSJ at Black Cat, leaving a roundabout (or two!) on the A1 mainline. I do see the advantage of that - could be that higher standard GSJs would be incompatible with some plausible A1/A1(M) routes.
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Re: Black Cat - Cambourne rumour?

Post by Chris5156 »

jackal wrote:From what Haydn says I guess the plan is just to build the A428 route with a 'bare minimum' GSJ at Black Cat, leaving a roundabout (or two!) on the A1 mainline. I do see the advantage of that - could be that higher standard GSJs would be incompatible with some plausible A1/A1(M) routes.
Ah, you read it as a dumbbell favouring the A421/A428 as the through route. I read it as a dumbbell favouring the A1.

The first would make a lot of sense if there were reasonably firm plans for the A1 to be upgraded; otherwise it risks turning into Alconbury further north on the A1, where the equally-busy-if-not-busier A14 is interrupted by an entirely inappropriate junction.

If it could be done without enormous extra cost, a two-bridge roundabout GSJ might be a better option; it would be no worse an interruption for the A1 than the existing roundabout so would present no disadvantage in the short term, while still not being too ridiculously over-specified for its future role as a local junction.
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Re: Black Cat - Cambourne rumour?

Post by jackal »

Chris5156 wrote:
jackal wrote:From what Haydn says I guess the plan is just to build the A428 route with a 'bare minimum' GSJ at Black Cat, leaving a roundabout (or two!) on the A1 mainline. I do see the advantage of that - could be that higher standard GSJs would be incompatible with some plausible A1/A1(M) routes.
Ah, you read it as a dumbbell favouring the A421/A428 as the through route. I read it as a dumbbell favouring the A1.

The first would make a lot of sense if there were reasonably firm plans for the A1 to be upgraded; otherwise it risks turning into Alconbury further north on the A1, where the equally-busy-if-not-busier A14 is interrupted by an entirely inappropriate junction.
They're between a rock and a hard place with this. If they build a dumbell and the A1 doesn't get upgraded then you have an Alconbury-style mess (I absolutely agree the A1 is the busier route). If they built a stackabout or freeflow effort at Black Cat, then the A1/A1(M) preferred route doesn't go through there, they've wasted possibly £100m. A third option would be to develop these as a joint scheme (or at least to a common timetable), but that would mean the A428 is delayed to the next road period at best and Black Cat stays as a flat roundabout, and perhaps no upgrade happens at all if there's a change of political priorities. I'm not sure any horn of the dilemma (or rather, trilemma) is particularly attractive, so I'm not going to be too sniffy if they go for the first one.
If it could be done without enormous extra cost, a two-bridge roundabout GSJ might be a better option; it would be no worse an interruption for the A1 than the existing roundabout so would present no disadvantage in the short term, while still not being too ridiculously over-specified for its future role as a local junction.
If a dumbell or roundabout interchange is built there the final arrangement could use it and the existing A1 as the connection between the two new grade-separated routes, similar to Chieveley.
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Re: Black Cat - Cambourne rumour?

Post by WHBM »

Chris5156 wrote: I am happy to let Highways England borrow my copy of the early 1990s plans for the A1(M) Baldock-Alconbury scheme so they can copy it.
Goodness me, the major consultancies, so well connected to the DfT, will NEVER let that happen. They will say they have to do a whole new study starting from scratch. The fact that it will absorb so much of the available budget that there's not enough left to actually construct the scheme is, of course, completely by the by.
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Re: Black Cat - Cambourne rumour?

Post by Derek »

But as we've discussed elsewhere, upgrading the A421/428 route to D2 will open the floodgates to traffic, effectively providing a bypass for the M25. It will be choked solid on the day of opening, never mind the impact on the A34. This is an obvious project to do, but doing it to D2 just isn't going to cut the mustard.

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Re: Black Cat - Cambourne rumour?

Post by jackal »

Derek wrote:But as we've discussed elsewhere, upgrading the A421/428 route to D2 will open the floodgates to traffic, effectively providing a bypass for the M25. It will be choked solid on the day of opening, never mind the impact on the A34. This is an obvious project to do, but doing it to D2 just isn't going to cut the mustard.
As I've mentioned before, there is actually very little traffic doing A421<->A428. The 2014 AADTs are:

17,364 A428 East of A1
53,267 A1 North of Black Cat
27,784 A421 West of Black Cat

The A421 only has 17,364AADT total, and much of that will not be coming to/from the A428. Even if A421<->A428 traffic increased by 500% it would still be within design limits for grade-separated D2!

Furthermore, looking at a map, there are very few routes that could conceivably be moved from the M25 to the A421/A428 with the Black Cat upgrade. I wouldn't be sure even of 50% traffic growth.

If you add on the MK-Oxford expressway then you start to get more induced traffic, but it's still only for a few very specific long distance routes. The vast majority of M25 traffic is more local and unaffected. Maybe 100% or 150% traffic growth on the A421-A428 corridor is possible once the full route is complete, but that's still comfortably inside D2 design limits.

With likely traffic levels the real choke points will be the A14 at Cambridge and the crappy M1/A421 junction. These will be the constraints, not the D2 between them.
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Re: Black Cat - Cambourne rumour?

Post by KeithW »

jackal wrote:It's more than a rumour - A428 Black Cat to Caxton Gibbet is committed for this road period (i.e. 2015-20 - see here, Part 2, p. 43). This means funding has been allocated to start construction by the end of 2019/20, so I'm expecting a big announcement soon. Probably the preparations for this are what OP is talking about.

There is a separate Oxford to Cambridge Expressway study, which is considering the whole corridor. Anything that comes out of this, such as options for filling the gap between the M1 and M40, will be much further down the line - it is intended only to inform the next RIS (i.e. for post-2020 improvements).
The problem is we have been here before.

There was a thread here back in 2010 entitled 'A421/A428 - is there a plan?'

There are some real engineering and planning problems for a road linking the A421 and A428. I dont think simply upgrading the existing section between Wyboston and the A1 down to the Black Cat is an option as there is too much local traffic and development at the St Neots/Wyboston end and of course the existing rail bridge over the A428 would need to be rebuilt.

The original commitment for the A14 improvement was made over a decade ago, planning studies were made and public hearings held. Then the next government cancelled it and we had to go through the whole thing again. The current scheme was supposedly given the green light in 2012. Five years on the only tangible work is the relatively minor improvement on the Girton interchange and the start of the works widening the A14 from Swavesey to Milton.

Given that and history the lack of even a formal study for this A428 improvement I see little chance that construction could start by 2019/20. Talk of of improvements to the Black Cat roundabout only raises my suspicions further. The only realistic option IMHO is a new road running south of the to the end of the A421 and this involves major works incuding new crossings of the Great Ouse and East Coast Main Line and replacing the Black Cat roundabout with a proper free flow GSJ. I would be pleasantly surprised if the planning and approvals required could be completed and signed off in under 5 years.
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Re: Black Cat - Cambourne rumour?

Post by KeithW »

Derek wrote:But as we've discussed elsewhere, upgrading the A421/428 route to D2 will open the floodgates to traffic, effectively providing a bypass for the M25. It will be choked solid on the day of opening, never mind the impact on the A34. This is an obvious project to do, but doing it to D2 just isn't going to cut the mustard.

Derek
Sorry I just don't see it. The A421 already provides a D2 route from the A1 to the M1 and the A14 is dualled to a high standard all the way to the M1/M6. Neither are particularly busy and the main problem with the A14 is the ridiculous Catthorpe interchange. Without a major upgrade of the Milton Keynes to M40/A43 route I see little reason to expect much traffic to try and 'bypass' the M25.

The main problems with the current A428/A421 route are these.

1) The D2 section of the A428 ends at Caxton Gibbet where you have a junction at grade with the A1198 which carries a lot of traffic to the A14 and from which the A428 continues as a rural S2 all the way to the A1 passing through major retail and light industrial parks. The result is daily congestion, massive tailbacks and a LOT of RTA's. This has been exacerbated in recent years by increased residential development, initially at Cambourne and more recently with the new housing at St Neots that has appeared east of the railway line which traditionally deleted the towns edge

2) The Black Cat itself which should have been replaced by a GSJ years ago instead of which we have seen a lot of fruitless tinkering.

The traffic along both routes is to a large extent local with long distance traffic being mainly that from the A14 carrying between Cambridge, Ipswich and Felixstowe to the North and West via the M1/M6 while the A428 carries traffic between East Anglia and the south and west via the A1 and M1.
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Re: Black Cat - Cambourne rumour?

Post by Chris5156 »

KeithW wrote:Given that and history the lack of even a formal study for this A428 improvement I see little chance that construction could start by 2019/20. Talk of of improvements to the Black Cat roundabout only raises my suspicions further. The only realistic option IMHO is a new road running south of the to the end of the A421 and this involves major works incuding new crossings of the Great Ouse and East Coast Main Line and replacing the Black Cat roundabout with a proper free flow GSJ. I would be pleasantly surprised if the planning and approvals required could be completed and signed off in under 5 years.
Upthread Haydn has already indicated that the plan is an off-line route from Black Cat, south of Little Barford, rejoining the line of the existing A428 east of St Neots and an upgrade from there to Caxton Gibbet.

Replacing Black Cat with a free-flowing GSJ will be a waste of time and money, for all the reasons already discussed: the A1 is likely to be moved onto a new line when it's upgraded so Black Cat will cease to be the point where the two major routes intersect sooner or later. And even in the interim a free-flowing GSJ is wasted because to both the north and south the A1 is seriously substandard.
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Re: Black Cat - Cambourne rumour?

Post by bazzapurple »

Thanks all.
It sounds promising, whenever it finally appears.
It looks as though the route will be mainly through agricultural land, so fairly quick once started.
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Re: Black Cat - Cambourne rumour?

Post by thatapanydude »

Nice to see that the A421 upgrade is coming at last, but what I don't get is why the A1 is taking the main line, not the A421. I know that the A1 is busier currently, but if the A1(M) is built then its unlikely to go via black cat meaning you're left with the A421 at a GSJ, which would have to be altered. It would save more money if the A421 took the mainline and when eventually the A1(M) is built, the dumbbell junction can be easily changed for a LAR assessing or even getting rid of the junction with out the need to completely destroy it because the A421 avoid its.
A1/A1(M) >>> M1
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Re: Black Cat - Cambourne rumour?

Post by Chris5156 »

thatapanydude wrote:Nice to see that the A421 upgrade is coming at last, but what I don't get is why the A1 is taking the main line, not the A421. I know that the A1 is busier currently, but if the A1(M) is built then its unlikely to go via black cat meaning you're left with the A421 at a GSJ, which would have to be altered. It would save more money if the A421 took the mainline and when eventually the A1(M) is built, the dumbbell junction can be easily changed for a LAR assessing or even getting rid of the junction with out the need to completely destroy it because the A421 avoid its.
I think it's generally understood, further up the thread, that the A421 will be taking the mainline through the junction, and the A1 will stop for a roundabout or two underneath it until such time as it's upgraded off line.
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