A428 Black Cat - Caxton Gibbet improvement

[Berk]

Ah, fair enough. Makes you wonder why didn't the BBC highlight those schemes instead??

They did mention them, of course, but Stonehenge was the one they thought would be canned.

[jackal]

Two explanations really. One is just about filling the news cycle. The decision I'm talking about was buried in the Autumn statement (see here) and the BBC had plenty of other stuff to report at the time. The other is just that breaking a commitment (like cancelling Stonehenge) would be bigger news than not making a commitment (like leaving the A1 East of England on the backburner).

[dcrc2]

Has this project been put back? Maybe I'm misremembering but I think the plan was to start in early 2020 if everything went well. But the timetable on the HE website now says:

Early 2020: Decision expected from the Secretary of State for Transport. If approved, the scheme will be included in the Government’s 2020-2025 Road Investment Strategy programme.

[jackal]

Nice catch. That statement seems unambiguous yet the scheme is still in the HE 2017/18 delivery plan for a 2019-20 start (see p. 60).

Perhaps they've delayed it since the plan was released on 1 August? Could be budgetary concerns or maybe to ensure that it fits in with the A1 plans.

[firefly]

Personally I think a three-level junction is unwarranted. It seems to me that:
- If we do eventually get an A1 upgrade it will surely be offline through Tempsford. Option A or C will be a monumental waste of money if the A1 moves away from here.
- If we don't get an A1 upgrade, then the quality of the A1 around here is so low that leaving a roundabout on the mainline isn't going to make a huge difference.

Unfortunately I can't support their option B either: depending on how you interpret the diagram, traffic from the A1 (northbound) to the A428 either doesn't have access to the new road, or would conflict with A1 southbound traffic. Either of these possibilities looks like a mistake.

So here's my variant of option B, moving the roundabout south of the A421-A428 and providing a dumbbell to the west to fill in the movements. I've drawn this as reusing the existing minor road bridge but maybe the bridge would need replacing with a larger version.

black_cat.png

Why do you too make it so complicated? The three proposals of Highways England look already terribly over-engineered. But why? The A1 between Sandy and St Neot isn't grade-separated. To get this status, it needs to be re-aligned. But that is a future project. And only with that second phase comes the final A1/A421/A428 junction, and not with this one. So nothing fancy, just a simple junction connecting local surface roads with a trunk route is all that is needed:

[jackal]

The scheme page has been updated. A couple of points of note:

1. The PRA has been delayed, apparently due to interactions with the A1 scheme:

Since the consultation, we have continued to develop the scheme by incorporating your feedback and carrying out technical assessments and surveys. We have also recognised the need to better understand the direction and incorporate potential changes from the A1 East of England Strategic Study.

This will require further analysis to fully understand the implications for the A428 scheme. This means that the preferred route announcement has not been possible in autumn 2017. We recognise that this delay may be frustrating, however it is important that the scheme meets the long term needs of local communities and road users throughout the region. We will update you on our progress and next steps early in the new year and share as much detail as possible.

The latest info on the A1 scheme makes it seem dubious whether it will go ahead at all. But as long as it's alive in some form there is a risk of a major rebuild of Black Cat being a white elephant. It will be interesting to see what they come up with here - they could just revert to a dumbell layout, perhaps similar to Firefly's sketch with major flows deconflicted, and leave it to the A1 scheme to provide a further improvement if required down the line?

2. There is an important change to the start date, which previously mentioned 'the Government’s 2020-2025 Road Investment Strategy programme', but now says 'If approved, construction will proceed in 2020'.

[jackal]

I've also noticed this from p. 36 of the recent NIC report:

expansion in and around the Sandy area in central Bedfordshire, and along the A1 corridor, potentially supporting the development of a large town, exploiting new East West Rail and existing north-south connectivity via the East Coast Main Line. Delivering major growth may require other changes such as the re-alignment of the A1, and potentially relocating the existing East Coast Main Line station;

https://www.nic.org.uk/wp-content/uploa ... sperty.pdf

[jackal]

A new A428 consultation is open: https://highwaysengland.citizenspace.co ... rovements/

The junctions at Cambridge Road and Caxton Gibbet are dumbbell GSJs. Black Cat itself remains a stacked roundabout, but it's now clear that they intend to construct an extensive local road network linking into it, almost entirely separating traffic from the villages to the north from the A1, and with the infamous marina access replaced with a bridge and link road to Black Cat. This all just deepens my doubts about the idea of a heavy strategic right turn being handled at a massive roundabout jammed full of local roads. Otherwise it looks a good scheme.

The previous consultation [correction: preferred route announcement] was as recent as February (some discussion here: viewtopic.php?f=1&t=36423&hilit=oxford+ ... &start=300). It seems they really want to get this through quickly, with the DCO to be submitted in early 2020.

[c2R]

Looking at the fly throughs, I'm not sure I should ever show my nephew that it is possible to get a real world job actually playing minecraft...

[danfw194]

A new A428 consultation is open: https://highwaysengland.citizenspace.co ... rovements/

The junctions at Cambridge Road and Caxton Gibbet are dumbbell GSJs. Black Cat itself remains a stacked roundabout, but it's now clear that they intend to construct an extensive local road network linking into it, almost entirely separating traffic from the villages to the north from the A1, and with the infamous marina access replaced with a bridge and link road to Black Cat. This all just deepens my doubts about the idea of a heavy strategic right turn being handled at a massive roundabout jammed full of local roads. Otherwise it looks a good scheme.

The previous consultation was as recent as February (some discussion here: viewtopic.php?f=1&t=36423&hilit=oxford+ ... &start=300). It seems they really want to get this through quickly, with the DCO to be submitted in early 2020.

Completely agree with you about the right turns at Black Cat, not promising, but I suppose we should be grateful for what's on offer given the current shambles.

This will be one half of the Cambridge-Oxford expressway completed at least.

[darkcape]

It seems they really want to get this through quickly, with the DCO to be submitted in early 2020.

Most of the current A14 workforce is pencilled in to move on to the A428 afterwards so the HE is under massive pressure from the contractors to have it ready on time and ensure continuous supply of work, something the HE committed themselves to a few years ago. The current M56 faff isn't doing much to reassure them at the moment.

[c2R]

The Caxton Gibbet proposal is a bit disappointing that better access issn't being proposed for the "service area" / fast food sheds - the current access is too close to the main roundabout and has the potential to suffer from increased accidents with fast moving traffic coming off the roundabout as cars try and pull out of the car park while being careful not to spill their drinks etc.

[KeithW]

Taken altogether it is rather better than I expected, the Caxton Gibbet junction looks good and as a once frequent used of the B1040 junction at Eltisley the new layout will remove one of the scariest junctions in South Cambridgeshire. The traffic flow through Caxton Gibbet will also be greatly improved, queues for the existing roundabout can be very long at peak.

I understand people's reservations about the roundabout at the Black Cat but the fact is the amount of turning traffic will be hugely reduced. As of today on either the A421/A428 route or the A1 everything is turning traffic. Headed east west you two turns. The first to have to get onto the A1 southbound at Wyboston and the second at the Black Cat where you have a relatively short stretch in which to get across to the right hand lane in time for the turn on to the A421. A real benefit will be the reduction of traffic through St Neots and Eaton Socon and along the old A428 to Eltiseley.

[trickstat]

Talking of right turns at the Black Cat, I don't think there is actually that much demand for northbound traffic from the A1 to turn right at the Black Cat towards Caxton Gibbet.

[jackal]

Talking of right turns at the Black Cat, I don't think there is actually that much demand for northbound traffic from the A1 to turn right at the Black Cat towards Caxton Gibbet.

I don't think any of the right turns are heavy except southbound to westbound. But that one is a big problem IMO. It will have to go through essentially nine at-grade junctions within a couple of hundred yards. A couple of them will be signalised from day 1 according to the detailed plans (https://highwaysengland.citizenspace.co ... ements.pdf). Seems a bit of a disaster zone in the making.

[KeithW]

Talking of right turns at the Black Cat, I don't think there is actually that much demand for northbound traffic from the A1 to turn right at the Black Cat towards Caxton Gibbet.

Well if you are heading from NW London to Cambourne, Cambridge and onwards to Ely or Norwich its a pretty good route which will be better once the Black Cat is sorted, The A505 is shorter but it gets pretty messy past Royston. Its certainly a route I would have used when living in South Cambs rather than hot dogging past Edworth to Dunton to pick up the B1042 . There was a time when I was living in Edgware and working in Cambridge when this was my daily commute but then I always was one of the awkward squad

That said I will agree its not a large volume of traffic. There will be rather more coming across the A421 from the M1/Milton Keynes and heading north up the A1 I suspect.

[trickstat]

Talking of right turns at the Black Cat, I don't think there is actually that much demand for northbound traffic from the A1 to turn right at the Black Cat towards Caxton Gibbet.

I don't think any of the right turns are heavy except southbound to westbound. But that one is a big problem IMO. It will have to go through essentially nine at-grade junctions within a couple of hundred yards. A couple of them will be signalised from day 1 according to the detailed plans (https://highwaysengland.citizenspace.co ... ements.pdf). Seems a bit of a disaster zone in the making.

It does seem that there is a distinct possibility that the improvements that will speed up journeys between Bedford/MK and Cambridge will slow those from various points north of St Neots and Bedford/MK/M1.

[KeithW]

Talking of right turns at the Black Cat, I don't think there is actually that much demand for northbound traffic from the A1 to turn right at the Black Cat towards Caxton Gibbet.

I don't think any of the right turns are heavy except southbound to westbound. But that one is a big problem IMO. It will have to go through essentially nine at-grade junctions within a couple of hundred yards. A couple of them will be signalised from day 1 according to the detailed plans (https://highwaysengland.citizenspace.co ... ements.pdf). Seems a bit of a disaster zone in the making.

Given that currently ALL the traffic on the A1 and A421/A428 goes through the Black Cat roundabout it cannot be anything other than an improvement. An all singing all dancing GSJ would be better but realistically not going to happen.

This is actually a route I regularly drove from Cambridge to Oxford and I really dont recall any major problems at the existing Black Cat making the westbound turn off the southbound A1. The congestion was predominantly from the Northbound A1 onto the A421 westbound. This is rather well seen on the Google satellite view.

https://www.google.co.uk/maps/@52.18368 ... a=!3m1!1e3

The important fact here is that A1 and A428/A421 which are the major traffic routes will be freeflow and the volume of traffic negotiating the roundabout will be greatly reduced. Given that the traffic flows are pretty obvious I rather doubt that vehicles will have more than one or two sets of traffic lights to deal with.

[jackal]

Talking of right turns at the Black Cat, I don't think there is actually that much demand for northbound traffic from the A1 to turn right at the Black Cat towards Caxton Gibbet.

I don't think any of the right turns are heavy except southbound to westbound. But that one is a big problem IMO. It will have to go through essentially nine at-grade junctions within a couple of hundred yards. A couple of them will be signalised from day 1 according to the detailed plans (https://highwaysengland.citizenspace.co ... ements.pdf). Seems a bit of a disaster zone in the making.

Given that currently ALL the traffic on the A1 and A421/A428 goes through the Black Cat roundabout it cannot be anything other than an improvement. An all singing all dancing GSJ would be better but realistically not going to happen.

This is actually a route I regularly drove from Cambridge to Oxford and I really dont recall any major problems at the existing Black Cat making the westbound turn off the southbound A1. The congestion was predominantly from the Northbound A1 onto the A421 westbound. This is rather well seen on the Google satellite view.

https://www.google.co.uk/maps/@52.18368 ... a=!3m1!1e3

What you are looking at there is a queue of A1 northbound traffic unable to enter the roundabout because of the heavy flow of A1sb to A421wb traffic. Hence why it was signalized and had other weird things done to it.

Of course, the new junction will be a great improvement, but I don't buy the argument that it's 'not realistic' to have freeflow for sb to wb when it was in two of the three consulted junction options: http://i.imgur.com/tJpf8yc.png The only reason we're not getting it is because the general public voted for a nice big roundabout

I also found a long list of Black Cat junction options in the Preliminary Environmental Information Report, including what sounds like a full freeflow design (option 4):

a. Option 1A – Dumbbell roundabouts on Roxton Road with merge and diverge slips
from A428 and A1 connecting to the two roundabouts.
b. Option 1B – Dumbbell roundabouts near the Black Cat roundabout with merge and
diverge slips from A428 and A1 connecting to the two roundabouts.
c. Option 1C – Similar to Option 1B with merge and diverge on the A428 located
further away from the mainline carriageway.
d. Option 1D – Dumbbell roundabouts on Roxton Road with merge and diverge slips
from A428 connecting to the two roundabouts. New roundabouts on the A1 with
merge and diverge slips from A1 connecting to the new roundabout, with a side
road connecting the roundabout on the A1 and southern roundabout at Roxton.
e. Option 1E – Dumbbell roundabouts on Roxton Road and A1 with merge and
diverge slips from A428 and A1 connecting to the two dumbbell roundabouts.
f. Option 2A – Dumbbell roundabouts on Roxton Road with diverge and merge from
A428 connecting to the roundabouts. Another dumbbell to the east of A1 with
diverge and merge from A428 connecting to these roundabouts with southbound
diverge and merge on A1 connecting to east roundabout and link roads connecting
east and west roundabouts.
g. Option 2B – One roundabout on Roxton Road with diverge and merge from A428
connecting to the roundabout. Another roundabout to the east of A1 with diverge
and merge from A428 connecting to this roundabout with southbound diverge,
merge on A1 and link roads connecting this roundabout.
h. Option 3A – One roundabout at the Black Cat roundabout with merge and diverge
slip roads from A428 and A1 connecting the roundabout.
i. Option 3B – Similar to Option 3A with merge and diverge on the A428 moved
further away from the mainline carriageway.
j. Option 4 – Junction with slip roads and interchange links for all directions. Loop
slip roads between A1 northbound and A428 eastbound as well as A1 southbound
and A428 westbound.
k. Option 5 – Eastbound diverge slip and westbound link from A428 connecting to A1
northbound and southbound respectively. Southbound diverge loop from A1
connecting to A428 westbound.
l. Option 6 – Eastbound diverge link road from A428 connecting to A1 northbound
and diverge slip connecting to the Black Cat roundabout. Southbound diverge link
road from A1 connecting to A428 westbound, and westbound merge slip on A428
connecting from the existing Black Cat roundabout.

The consulted options (A, B and C) are related to these as follows:

a. Option A – Forming a combination of Options 1A and 1C, this comprised a threetiered roundabout, removing the existing Black Cat roundabout, and involved the
construction of two roundabouts to the west of the existing roundabout. A new freeflow continuous link from the A421 eastbound towards the A1 northbound would be
created along with slip roads to and from the A421, the A1 and the A428. With this
option the A1 would become a free-flow continuous road going under the slip roads.
b. Option B – Based on Option 6, this comprised a two-tiered roundabout, retaining
the existing Black Cat roundabout and would create a new free-flow continuous link
from the A421 eastbound towards the A1 northbound. The addition of slip roads
would provide a free-flow link, bypassing traffic moving southbound onto the A421,
with the A1 remaining the same.
c. Option C – Based on Option 3B, this comprised a three-tiered junction, enlarging
the Black Cat roundabout and creating a new free-flow continuous link from the
A421 eastbound towards the A1 northbound. Slip roads would be built from the
A421 to the A1, and the A428 and the A1 would become a continuous free-flow
road under the widened Black Cat roundabout.

Couldn't find any plans of the longlisted options unfortunately.

https://highwaysengland.citizenspace.co ... ME%201.pdf

[Truvelo]

A1 southbound to A421 westbound could be improved by hamburgerising that movement so it bypasses the LAR and A428 entry points.