A46 Coventry Junctions upgrade

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mattling
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Re: A46 Coventry Junctions upgrade

Post by mattling » Tue Aug 18, 2020 00:17

The French junction has a 50km/h speed limit which would be another issue.

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Alderpoint
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Re: A46 Coventry Junctions upgrade

Post by Alderpoint » Tue Aug 18, 2020 06:43

mattling wrote:
Tue Aug 18, 2020 00:17
The French junction has a 50km/h speed limit which would be another issue.
That's quicker than you can go around the Walsgrave roundabout at the moment.

IMO (going through there twice a day when I go to to the office), N to S could be done by new lanes to the east of the existing roundabout although land-grab would need to minimised. In the opposite direction, a flyover over the top of the existing roundabout should be feasible. Okay, this is not result in a NSL junction, but that doesn't seem to be a problem these days (e.g. the 50mph Toll Bar upgrade).

Alternative would be to close the existing junction totally and provide a new GSJ half a mile to the north to serve B4082 and also provide direct access into the back of the hospital. Probably too radical....
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jackal
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Re: A46 Coventry Junctions upgrade

Post by jackal » Tue Aug 18, 2020 07:32

Here there's not much point in elaborate layouts that compromise the mainline like that French one. Just take the A46 through on the smoothest line you can, then stick in a three arm dumbbell or diamond (with retaining walls to save space). This gives a higher speed limit for the mainline and no right hand entry/exit.

ais523
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Re: A46 Coventry Junctions upgrade

Post by ais523 » Tue Aug 18, 2020 20:00

Re: mattling's suggestion, you can move the "straight on" that's a left turn (when driving on the left; right turn in the French example) to the inside of the junction rather than the outside, while keeping the geometry otherwise the same; then you just end up with a regular trumpet, with all the entries and exits on the correct sides of the road. The only real downside to this is that you end up with a merge/diverge (depending on which way round you build the junction) on the inside of a fairly sharp bend, which might be a safety issue in its own right; that's presumably why the example above sends the straight-on around the outside of the junction instead.

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jackal
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Re: A46 Coventry Junctions upgrade

Post by jackal » Sun Dec 05, 2021 14:51

Beams are being lifted for the Binley grade separation this weekend, with lots of disruption:

https://www.bbc.co.uk/news/uk-england-c ... e-59510056

I believe there has been some delay with it due to poor weather.

DfT info indicates that the Walsgrave contract is being procured at £43.8m, so a bit less than Binley, which was £61m. This suggests they are going for a relatively straightforward layout with only a single bridge.

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Re: A46 Coventry Junctions upgrade

Post by darkcape » Mon Dec 06, 2021 22:28

From what I was told they recovered the time lost due to the wind and its all ok for next weekend's closure.
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Re: A46 Coventry Junctions upgrade

Post by jervi » Tue Dec 07, 2021 09:36

Drove along the A46 to Coventry this weekend, and at the start of the closure there were "road closed" signs as you would expect, but in addition there are no cycling, no pedestrians & no horses signs on both carriageways. Just though I'd point that out since I've never seen road works signed this way before - although I does make total sense since a "road closed" sign does only apply to motor vehicles.

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Alderpoint
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Re: A46 Coventry Junctions upgrade

Post by Alderpoint » Tue Dec 07, 2021 11:09

jervi wrote:
Tue Dec 07, 2021 09:36
Drove along the A46 to Coventry this weekend, and at the start of the closure there were "road closed" signs as you would expect, but in addition there are no cycling, no pedestrians & no horses signs on both carriageways. Just though I'd point that out since I've never seen road works signed this way before - although I does make total sense since a "road closed" sign does only apply to motor vehicles.
The no cycling, no pedestrians & no horses signs have been there for months (probably since the start of the works but I wasn't going that way then).
The A465 Heads of the Valley road through Clydach gorge was signposted no cycling throughout the roadworks - but uphill only!

I came through this morning and the half of the main beams are installed (presumably the remainder next weekend). It's going to be a big flyover - reminds me somewhat of Stonebridge.
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jackal
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Re: A46 Coventry Junctions upgrade

Post by jackal » Tue Dec 07, 2021 12:10

Yes, it's a multispan bridge across the roundabout. They were planning to use retaining walls for the central section but there was a bit of pushback about creating a barrier across the junction. The long flyover opens things up a bit more for NMUs and (though they didn't say it) gives options for future layout changes such as hamburgerisation. There's not the space for the planted embankments you see at larger GSJs.

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Chris5156
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Re: A46 Coventry Junctions upgrade

Post by Chris5156 » Tue Dec 07, 2021 22:04

jackal wrote:
Tue Dec 07, 2021 12:10
The long flyover opens things up a bit more for NMUs and (though they didn't say it) gives options for future layout changes such as hamburgerisation.
Or, in a parallel universe where elaborate signalisation of roundabouts isn’t the only game in town, a SPUI or a diverging diamond…
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JammyDodge
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Re: A46 Coventry Junctions upgrade

Post by JammyDodge » Thu Dec 09, 2021 20:17

Chris5156 wrote:
Tue Dec 07, 2021 22:04
Or, in a parallel universe where elaborate signalisation of roundabouts isn’t the only game in town
Tell that to Durham CC, with the monstrosities they made where the A690 meets the A691 and where the A690 meets the New Elvet Bridge

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Bryn666
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Re: A46 Coventry Junctions upgrade

Post by Bryn666 » Mon Dec 13, 2021 23:59

JammyDodge wrote:
Thu Dec 09, 2021 20:17
Chris5156 wrote:
Tue Dec 07, 2021 22:04
Or, in a parallel universe where elaborate signalisation of roundabouts isn’t the only game in town
Tell that to Durham CC, with the monstrosities they made where the A690 meets the A691 and where the A690 meets the New Elvet Bridge

Just :hurl:
Those provide absolutely none of the benefits of anything, that hamburger ar the first example can fit a single car in it.

Why not just have a conventional signal controlled crossroads which would at least have allowed pedestrians and cyclists to get across in one piece as well?

Traffic engineers that know nothing about traffic trying to be clever once again.
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JammyDodge
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Re: A46 Coventry Junctions upgrade

Post by JammyDodge » Tue Dec 14, 2021 06:35

Bryn666 wrote:
Mon Dec 13, 2021 23:59
JammyDodge wrote:
Thu Dec 09, 2021 20:17
Chris5156 wrote:
Tue Dec 07, 2021 22:04
Or, in a parallel universe where elaborate signalisation of roundabouts isn’t the only game in town
Tell that to Durham CC, with the monstrosities they made where the A690 meets the A691 and where the A690 meets the New Elvet Bridge

Just :hurl:
Those provide absolutely none of the benefits of anything, that hamburger ar the first example can fit a single car in it.

Why not just have a conventional signal controlled crossroads which would at least have allowed pedestrians and cyclists to get across in one piece as well?

Traffic engineers that know nothing about traffic trying to be clever once again.
That's literally my question. A regular intersection would arguably function better and be less confusing and be more aesthetically pleasing
These 2 junction have over 60 traffic lights, which is a stupid amount for 2 junctions both with 4 arms
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Debaser
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Re: A46 Coventry Junctions upgrade

Post by Debaser » Wed Dec 15, 2021 06:30

JammyDodge wrote:
Tue Dec 14, 2021 06:35
Bryn666 wrote:
Mon Dec 13, 2021 23:59
JammyDodge wrote:
Thu Dec 09, 2021 20:17


Tell that to Durham CC, with the monstrosities they made where the A690 meets the A691 and where the A690 meets the New Elvet Bridge

Just :hurl:
Those provide absolutely none of the benefits of anything, that hamburger ar the first example can fit a single car in it.

Why not just have a conventional signal controlled crossroads which would at least have allowed pedestrians and cyclists to get across in one piece as well?

Traffic engineers that know nothing about traffic trying to be clever once again.
That's literally my question. A regular intersection would arguably function better and be less confusing and be more aesthetically pleasing
These 2 junction have over 60 traffic lights, which is a stupid amount for 2 junctions both with 4 arms
Fixation. There's already a roundabout in place so we must use as much of that as we can (otherwise it might look to the layman that the roundabout was a mistake, I mean, just look at all that land take).

Too often the designer doesn't seem able to take a step back, ignore the current form of the junction and just see each arm individually, each of a certain class and number of lanes, and then look to how best join up those lanes based on the traffic flows, keeping the whole thing compact and stoplines close together. It's a problem that seems endemic amongst engineers looking at the designs floating about out there.

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Alderpoint
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Re: A46 Coventry Junctions upgrade

Post by Alderpoint » Wed Dec 15, 2021 08:20

Alderpoint wrote:
Tue Dec 07, 2021 11:09
I came through this morning and the half of the main beams are installed (presumably the remainder next weekend).
All the main deck beams are now in place. I'm starting to believe the "Spring 2022" opening date.
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ABB125
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Re: A46 Coventry Junctions upgrade

Post by ABB125 » Mon Jan 10, 2022 20:23

A consultation on Walsgrave junction opens tomorrow. However, documents are now available here:
https://highwaysengland.citizenspace.co ... walsgrave/

Consultation brochure:
https://highwaysengland.citizenspace.co ... ochure.pdf

The preferred option is... a dumbbell about 800m north of the current roundabout. 50mph through the site of the current roundabout (a 70mph option was discounted). There's a lengthy list of alternatives that were discounted.
Capture.PNG
Personally I don't think it's too bad (with the caveat that I know nothing about the area or turning traffic flows). It could've been worse... (like the rejected signalised T-junction :D)

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Re: A46 Coventry Junctions upgrade

Post by Mapper89062 » Mon Jan 10, 2022 21:11

This looks like a decent solution given the constraints of the area and road alignments - I'd have liked the 70mph option, but it's a luxury, and a 50mph limit might have been necessary anyway given the weaving space to the M6 junction will be a bit tight. I'm relieved 3 (and also 1) were rejected quickly as well.

Looking at all the discarded options, the one obvious option that seems missing is LILOing the roundabout as in 7/8, but providing the missing movements via slips at the B4027 bridge, forming effectively a very large compact GSJ. Something like this:
tempsnip.png
tempsnip.png (267.23 KiB) Viewed 165 times
This wouldn't be very practical given the weaving distance to the south, but I'm surprised it was never on the initial assessment at all.

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Alderpoint
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Re: A46 Coventry Junctions upgrade

Post by Alderpoint » Mon Jan 10, 2022 22:32

Mapper89062 wrote:
Mon Jan 10, 2022 21:11
This looks like a decent solution given the constraints of the area and road alignments - I'd have liked the 70mph option, but it's a luxury, and a 50mph limit might have been necessary anyway given the weaving space to the M6 junction will be a bit tight. I'm relieved 3 (and also 1) were rejected quickly as well.
Agreed, I guess the option for a full roundabout rather than a dumbell for the GSJ would result in too much land take. However I do hope 50mph limit does not end up going all the way between the end of the M69 and the A46/A45 Stivichall/Festival Island - not that anyone obeys the existing 50 limits thereabouts
Looking at all the discarded options, the one obvious option that seems missing is LILOing the roundabout as in 7/8, but providing the missing movements via slips at the B4027 bridge, forming effectively a very large compact GSJ. Something like this:

tempsnip.png

This wouldn't be very practical given the weaving distance to the south, but I'm surprised it was never on the initial assessment at all.
This would have meant traffic to/from Walsgrave Hospital going along the residential section of Clifford Bridge Road south of the Sowe Bridge/Tescos roundabouts - it's busy enough there already.
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Re: A46 Coventry Junctions upgrade

Post by SouthWest Philip » Mon Jan 10, 2022 22:39

ABB125 wrote:
Mon Jan 10, 2022 20:23
The preferred option is... a dumbbell about 800m north of the current roundabout. 50mph through the site of the current roundabout (a 70mph option was discounted). There's a lengthy list of alternatives that were discounted.
Capture.PNG
I can't see the land surrounding this new junction staying undeveloped for very long. It's clearly designed to allow other entrances to be tacked on. At least we've been spared another flat roundabout, Witney or Gloucester bypass style.

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jackal
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Re: A46 Coventry Junctions upgrade

Post by jackal » Mon Jan 10, 2022 23:22

I always expected it to be a dumbbell but I'm a bit disappointed about the 50mph limit. It's not exactly Air Balloon terrain. They claim the realignment for 70mph creates flooding risks but they only seem to have looked at one line. Still not a bad scheme.

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