How much do GSJs cost to build?

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qwertyK
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How much do GSJs cost to build?

Post by qwertyK »

Odd question but a ballpark figure, how much for a GSJ over a NSL, National Highways dual carriageway? A roundabout with slip roads to and from each carriageway
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jervi
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Re: How much do GSJs cost to build?

Post by jervi »

Too much.

Depends on standards. But recently completed GSJs on motorways (which is a NSL dual carriageway):
M49 J1 - £50m
M11 J7a - £39.5m

I can't find costs of any new GSJs on a non-motorway dual carriageway for new junctions I can think of (Highwood (A24/A264) & Spittlegate (A1/A52)), but I'd presume just for the junction you are looking at £20-£25m for it to be built to 120kph specs.

Others may have a better estimates, but it does depend on a whole host of variables.
darkcape
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Re: How much do GSJs cost to build?

Post by darkcape »

jervi wrote: Tue Aug 02, 2022 23:28 Too much.

Depends on standards. But recently completed GSJs on motorways (which is a NSL dual carriageway):
M49 J1 - £50m
M11 J7a - £39.5m

I can't find costs of any new GSJs on a non-motorway dual carriageway for new junctions I can think of (Highwood (A24/A264) & Spittlegate (A1/A52)), but I'd presume just for the junction you are looking at £20-£25m for it to be built to 120kph specs.

Others may have a better estimates, but it does depend on a whole host of variables.
Yup, £25-30m for smaller GSJs. It depends on too much nowadays to be an easy figure.
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RJDG14
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Re: How much do GSJs cost to build?

Post by RJDG14 »

I would say that it depends on the layout of the junction. I suspect a full roundabout either over or under the road will be more expensive than a dumbell junction since the second requires just one bridge.
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c2R
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Re: How much do GSJs cost to build?

Post by c2R »

It also depends where in the country (i.e. land cost), and whether it's being built as part of a new build scheme, or whether existing traffic needs to be taken into account.
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KeithW
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Re: How much do GSJs cost to build?

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trickstat
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Re: How much do GSJs cost to build?

Post by trickstat »

c2R wrote: Wed Aug 03, 2022 07:21 It also depends where in the country (i.e. land cost), and whether it's being built as part of a new build scheme, or whether existing traffic needs to be taken into account.
The most expensive ones would presumably be in the south-east of England and would involve disruption of existing routes plus buying land that might have potentially been used for housing.
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Alderpoint
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Re: How much do GSJs cost to build?

Post by Alderpoint »

c2R wrote: Wed Aug 03, 2022 07:21 It also depends where in the country (i.e. land cost), and whether it's being built as part of a new build scheme, or whether existing traffic needs to be taken into account.
£61m for the new Coventry Binley Roundabout, which was supposedly built within the existing road boundary so no land cost.

But the new Walsgrave junction is set to cost up to £125m despite only requiring a single new bridge, presumably because the re-routing of the main carriageway and the (agricultural) land take.
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jackal
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Re: How much do GSJs cost to build?

Post by jackal »

£50m has been the norm for a two-bridge roundabout. Binley was about £60m as it's in a constrained space with a lot of structural content. About £40m for a dumbbell.

However, such an exercise is always backward looking. For a scheme designed today and opening on 5-10 years you are looking at a fair bit more due to inflation.

Also, as soon as you start rerouting or adding roads costs escalate significantly. Walsgrave, Testos, and M20 J10a were all £100m+, and though these are nominally junction schemes, probably half the costs are actually for new roads as opposed to the junction proper.

Offhand I can't think of a recent compact GSJ that was built as a discrete scheme, but I'd say £20m-£30m (plus inflation).
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wrinkly
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Re: How much do GSJs cost to build?

Post by wrinkly »

50 years ago GSJs started at about £1M.
Altnabreac
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Re: How much do GSJs cost to build?

Post by Altnabreac »

Winchburgh J1B on the M9 is coming in somewhere around £30m:
https://www.newcivilengineer.com/latest ... 7-04-2022/

£40m scheme value but that includes a new distributor road with road and rail bridges as well so the junction portion is likely only £30m. The existing road is able to be entirely closed during construction and no new bridge over or under the motorway is required which helps keep costs down.
qwertyK
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Re: How much do GSJs cost to build?

Post by qwertyK »

Woah, thats a lot more than I thought.

I'm working with an Essex borough council for a scheme that would require a new GSJ over the A12.
What was the justifiation for M11 J7A, I believe that was an Essex CC funded project rather than NH? Was it the prospect of a new hospital being built there in the future or the Harlow Gilston Garden town?
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Disgruntled Goat
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Re: How much do GSJs cost to build?

Post by Disgruntled Goat »

qwertyK wrote: Wed Aug 03, 2022 14:58 Woah, thats a lot more than I thought.

I'm working with an Essex borough council for a scheme that would require a new GSJ over the A12.
What was the justifiation for M11 J7A, I believe that was an Essex CC funded project rather than NH? Was it the prospect of a new hospital being built there in the future or the Harlow Gilston Garden town?
You also have to consider that all M11 traffic heading to/from Harlow only had one junction serving it and the A414 couldn't really cope.
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orudge
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Re: How much do GSJs cost to build?

Post by orudge »

The A90/A937 Laurencekirk junction was described as a £24m scheme in January 2016 (design and construction), but given it hasn't actually been built yet, who knows what the final cost will actually be.
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jackal
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Re: How much do GSJs cost to build?

Post by jackal »

orudge wrote: Wed Aug 03, 2022 16:23 The A90/A937 Laurencekirk junction was described as a £24m scheme in January 2016 (design and construction), but given it hasn't actually been built yet, who knows what the final cost will actually be.
Altnabreac wrote: Wed Aug 03, 2022 14:20 Winchburgh J1B on the M9 is coming in somewhere around £30m:
https://www.newcivilengineer.com/latest ... 7-04-2022/

£40m scheme value but that includes a new distributor road with road and rail bridges as well so the junction portion is likely only £30m. The existing road is able to be entirely closed during construction and no new bridge over or under the motorway is required which helps keep costs down.
It's been noted previously that Scottish schemes are cheaper than English ones, and that this can't be explained by obvious things like land costs (which are a tiny part of the cost of a typical English scheme). Possibly it is partly just an accounting difference.

I think at Winchburgh they are re-using the existing B8020 bridge, which significantly reduces costs.
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Re: How much do GSJs cost to build?

Post by KeithW »

wrinkly wrote: Wed Aug 03, 2022 14:17 50 years ago GSJs started at about £1M.
And you could buy a house in the NE for £3000, welcome to the wonderful world of inflation.
jnty
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Re: How much do GSJs cost to build?

Post by jnty »

KeithW wrote: Wed Aug 03, 2022 17:53
wrinkly wrote: Wed Aug 03, 2022 14:17 50 years ago GSJs started at about £1M.
And you could buy a house in the NE for £3000, welcome to the wonderful world of inflation.
By the general inflation measure, £1m then would apparently be roughly £9.5m in 2022. Of course, construction cost inflation runs higher than regular inflation - just as house price inflation does.

There will also be aspect of 'low hanging fruit' - back in the 70s we were still building 'easy' GSJs, often on newbuild roads in areas with low land prices connecting to less busy roads. Having got all the 'easy' roadbuilding mostly done last century, we're now left with projects which were avoided then, probably due to cost or complexity, or upgrading previous junctions which have been built around and lie on roads which are now far busier. These projects will naturally be much more expensive. A perfect example would be to compare the A74(M) upgrade done in the 90s over mostly open countryside to the M74 extension done this century through urban Glasgow. The latter was far, far more expensive per km, and while some of this will be down to inflation, the real reason is that the hardest bit was left till last.
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Re: How much do GSJs cost to build?

Post by AndyB »

It’s also complicated by junctions being done on the cheap having to be redone right later, which is always expensive.
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