New GSJ on A45, Coventry

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jackal
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New GSJ on A45, Coventry

Post by jackal »

No, not the one on Stonebridge Highway, but west of Coventry at the Eastern Green Sustainable Urban Extension (newspeak for thousands of greenbelt houses).

The junction will consist of a pair of LILOs feeding directly into roundabouts with a bridge connecting them. The eastbound LILO is at Brick Hill Lane while the westbound one is 500m east, presumably to increase weaving distance to the B4104. Pickford Green Lane will be disconnected from the A45.

One of the roundabouts is "pointless" as it has no arms other than the slips and the link road, and is presumably used to save money on geometry. I'm not too critical of the design though as it's a lot better than throwing an at-grade junction on the mainline.

Plans: https://www.google.com/url?sa=t&source= ... 8001379929

Local press: https://www.google.com/amp/s/www.covent ... 466987.amp

Bridge contract: https://bidstats.uk/tenders/2020/W52/741539852
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c2R
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Re: New GSJ on A45, Coventry

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jackal wrote: Tue Aug 03, 2021 16:24 No, not the one on Stonebridge Highway, but west of Coventry at the Eastern Green Sustainable Urban Extension (newspeak for thousands of greenbelt houses).
I love it - it's definitely sustainable with its direct link to the strategic road network!
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Re: New GSJ on A45, Coventry

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jackal wrote: Tue Aug 03, 2021 16:24 One of the roundabouts is "pointless" as it has no arms other than the slips and the link road, and is presumably used to save money on geometry. I'm not too critical of the design though as it's a lot better than throwing an at-grade junction on the mainline.
Given that they got rid of a horrid at grade junction east of Ryton only a few years back, I think people would have kicked off if this one was some at-grade traffic light mess. Seen worse designs, looks like a typical compact GSJ. I'm sure they'll plonk a Costa/Starbucks/Greggs on that pointless roundabout :wink: Hopefully the on-slips will be better than some of the A1 ones.
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jackal
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Re: New GSJ on A45, Coventry

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My guess is it exceeds DMRB traffic thresholds for a compact GSJ, so the pointless rbt is a clever workaround to make it technically a full GSJ. If the roundabout wasn't there the link road would be a slip road, which for a full GSJ can't be S2, and the radius would also have to be bigger.
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Re: New GSJ on A45, Coventry

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jackal wrote: Wed Aug 04, 2021 08:54 My guess is it exceeds DMRB traffic thresholds for a compact GSJ, so the pointless rbt is a clever workaround to make it technically a full GSJ. If the roundabout wasn't there the link road would be a slip road, which for a full GSJ can't be S2, and the radius would also have to be bigger.
It's a definite fudge to get around DMRB's ridiculous radii requirements.
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Re: New GSJ on A45, Coventry

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jackal wrote: Wed Aug 04, 2021 08:54 My guess is it exceeds DMRB traffic thresholds for a compact GSJ, so the pointless rbt is a clever workaround to make it technically a full GSJ. If the roundabout wasn't there the link road would be a slip road, which for a full GSJ can't be S2, and the radius would also have to be bigger.
This is exactly the sort of insight that would cause me to press “like” or “upvote” or similar, if the forum had that feature. But it doesn’t so I’ll just say that this is a brilliant observation. Thanks!
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Re: New GSJ on A45, Coventry

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If that is right it is absolutely ludicrous. Extra construction required for exactly the same outcome, not to mention the extra emissions from slowing down and speeding up. Nuts
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Re: New GSJ on A45, Coventry

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Herned wrote: Wed Aug 04, 2021 10:49 If that is right it is absolutely ludicrous. Extra construction required for exactly the same outcome, not to mention the extra emissions from slowing down and speeding up. Nuts
Yeah, if this is what DMRB actually produces, through omission rather than inclusion, something has to change!
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Re: New GSJ on A45, Coventry

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DB617 wrote: Wed Aug 04, 2021 11:09
Herned wrote: Wed Aug 04, 2021 10:49 If that is right it is absolutely ludicrous. Extra construction required for exactly the same outcome, not to mention the extra emissions from slowing down and speeding up. Nuts
Yeah, if this is what DMRB actually produces, through omission rather than inclusion, something has to change!
It's all there in CD 122. 30k is the max on the mainline for a compact GSJ - there's 40k here so they need a full GSJ. "Full grade separated connector road geometry 5.1 Two way slip roads shall be in the form of a dual carriageway with opposing traffic separated by a physical central reserve with vehicle restraint system". Not to mention 70kph rather than 30kph slip road design speed. Oh noes, our £25m junction just went to £50m! Not to worry, I've got a roundabout for that.
Chris5156 wrote: Wed Aug 04, 2021 10:38
jackal wrote: Wed Aug 04, 2021 08:54 My guess is it exceeds DMRB traffic thresholds for a compact GSJ, so the pointless rbt is a clever workaround to make it technically a full GSJ. If the roundabout wasn't there the link road would be a slip road, which for a full GSJ can't be S2, and the radius would also have to be bigger.
This is exactly the sort of insight that would cause me to press “like” or “upvote” or similar, if the forum had that feature. But it doesn’t so I’ll just say that this is a brilliant observation. Thanks!
You're welcome!
Last edited by jackal on Wed Aug 04, 2021 11:39, edited 1 time in total.
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Re: New GSJ on A45, Coventry

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DB617 wrote: Wed Aug 04, 2021 11:09
Herned wrote: Wed Aug 04, 2021 10:49 If that is right it is absolutely ludicrous. Extra construction required for exactly the same outcome, not to mention the extra emissions from slowing down and speeding up. Nuts
Yeah, if this is what DMRB actually produces, through omission rather than inclusion, something has to change!
CD122 has all the dry and boring detail, but it is basically impossible to provide even a compact GSJ without huge land take. It also shows why we only build 3 level roundabouts to connect roads as first resort, as the blurb for these basically sells them straight off. They even go as far as saying loops are a disadvantage in GSJ design, well of course they are, DMRB requires them to be the size of Texas. This is also why we don't build trumpets any more, instead favouring a sodding roundabout.

I hate the entire thing, it gold plates everything and makes roads cost far more than they should, but you probably know that already.
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Re: New GSJ on A45, Coventry

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Bryn666 wrote: Wed Aug 04, 2021 11:38
I hate the entire thing, it gold plates everything and makes roads cost far more than they should, but you probably know that already.
It gold plates everything except the merge with the main line, where you're essentially allowed to build bad things like Carpenter's Lodge with it's sharp corners followed by a merge in about three car lengths into a platoon of HGVs
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