Tightest Curve on a Motorway?

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DB124
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Tightest Curve on a Motorway?

Post by DB124 »

Not very original, I know.
But, this question comes in two parts:
-Which is the tightest curve on the mainline of a motorway?
-and which is the tightest curve under motorway restrictions?

For the former, my intuition tells me M90 Balmanno Hill or Queensferry, though it is possible that an urban motorway has a sharper curve (A167(M), M4). I haven't included Simister or Worsley because neither were designed as a mainline motorway.

For the latter, a more interesting task is presented. For example, this one west of Newport seems ludicrous. And whoever thought two lanes was a safe idea at Tebay needs to be fired. Is there a cloverleaf loop tighter than these? Or perhaps a really nasty roundabout approach with some awkward corners?

Would love to hear everyone's thoughts and insights on corners with Blue Signs. :)
SteelCamel
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Re: Tightest Curve on a Motorway?

Post by SteelCamel »

I think it would be hard to beat the M77N to M8W slip. Where else will you see "Max Speed 15" while under Motorway regulations? It's also under a mandatory 30mph limit and 2m width limit - large vehicles need to leave the motorway and use the roundabout instead.
AlexBr967
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Re: Tightest Curve on a Motorway?

Post by AlexBr967 »

I could be wrong but I believe this could be the tightest on a mainline. For tightest under motorway restrictions I reckon this might be a contender unless posting spaghetti is cheating.
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JammyDodge
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Re: Tightest Curve on a Motorway?

Post by JammyDodge »

SteelCamel wrote: Mon Dec 20, 2021 18:28 I think it would be hard to beat the M77N to M8W slip. Where else will you see "Max Speed 15" while under Motorway regulations? It's also under a mandatory 30mph limit and 2m width limit - large vehicles need to leave the motorway and use the roundabout instead.
I think the A58(M) might have it beat, with this.
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Mapper89062
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Re: Tightest Curve on a Motorway?

Post by Mapper89062 »

The A483 to M4 slip road at Swansea is very tight, and while I don't think it's quite the tightest curve, it must have one of the largest angles on a motorway slip road.
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swissferry
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Re: Tightest Curve on a Motorway?

Post by swissferry »

Mapper89062 wrote: Mon Dec 20, 2021 18:43 The A483 to M4 slip road at Swansea is very tight, and while I don't think it's quite the tightest curve, it must have one of the largest angles on a motorway slip road.
Reminds me of M8 junction 15.
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Re: Tightest Curve on a Motorway?

Post by DavidBrown »

Can't believe we've got this far and not mentioned M50 J3 yet. They've even replaced the ADS, as it seems showing it as a side road just wasn't enough!

Whilst nowhere near a winner, one that did surprise me when I has cause to use it for the first time the other week is the M25 C/W to M11 S free flow slip. The surprise was more so that it started off as a fairly shallow curve, which tightens up quite significantly.
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Re: Tightest Curve on a Motorway?

Post by FtoE »

DB124 wrote: Mon Dec 20, 2021 18:17 Not very original, I know.
But, this question comes in two parts:
-Which is the tightest curve on the mainline of a motorway?
-and which is the tightest curve under motorway restrictions?

For the former, my intuition tells me M90 Balmanno Hill or Queensferry, though it is possible that an urban motorway has a sharper curve (A167(M), M4). I haven't included Simister or Worsley because neither were designed as a mainline motorway.

For the latter, a more interesting task is presented. For example, this one west of Newport seems ludicrous. And whoever thought two lanes was a safe idea at Tebay needs to be fired. Is there a cloverleaf loop tighter than these? Or perhaps a really nasty roundabout approach with some awkward corners?

Would love to hear everyone's thoughts and insights on corners with Blue Signs. :)
The M90 southbound at Craigend (J10) was until a few years ago a tight two-lane

https://goo.gl/maps/wHhW4sfoezwV5uXb8
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Re: Tightest Curve on a Motorway?

Post by mikehindsonevans »

I mentioned this, the last time someone asked the question a couple of years ago.

The southern end of the M271, running into Southampton for the Western docks, ends in a stunningly-tight right-hander under a footbridge. Years back, someone stuffed a large vehicle into the footbridge support - at which point the investigation revealed that the bend was tighter than should have been "allowed".
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Re: Tightest Curve on a Motorway?

Post by Bfivethousand »

DavidBrown wrote: Mon Dec 20, 2021 21:13 Can't believe we've got this far and not mentioned M50 J3 yet. They've even replaced the ADS, as it seems showing it as a side road just wasn't enough!
Needed doing. And a nice tidy job has been done of it...
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ajuk
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Re: Tightest Curve on a Motorway?

Post by ajuk »

What about the tightest curve on any D2 where both lanes do it?
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owen b
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Re: Tightest Curve on a Motorway?

Post by owen b »

ajuk wrote: Tue Dec 21, 2021 02:39 What about the tightest curve on any D2 where both lanes do it?
The A171 is pretty tight here : https://www.google.co.uk/maps/@54.52574 ... a=!3m1!1e3
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Re: Tightest Curve on a Motorway?

Post by Micro The Maniac »

Mapper89062 wrote: Mon Dec 20, 2021 18:43 The A483 to M4 slip road at Swansea is very tight, and while I don't think it's quite the tightest curve, it must have one of the largest angles on a motorway slip road.
The A417 to M5(N) is a tad tight too... the first time I used it, I had a real seat of the pants moment, not expecting it to be *that* tight
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Re: Tightest Curve on a Motorway?

Post by Micro The Maniac »

mikehindsonevans wrote: Mon Dec 20, 2021 22:34 The southern end of the M271, running into Southampton for the Western docks, ends in a stunningly-tight right-hander under a footbridge. Years back, someone stuffed a large vehicle into the footbridge support - at which point the investigation revealed that the bend was tighter than should have been "allowed".
I don't get this.

The M271 ends at the Redbridge roundabout, doesn't it - wasn't not a free-flow (although will be soon, if not already) ??? And the final bit before the roundabout, while a bend, is nothing outrageous, especially on the approach to a terminating roundabout?

Plus the footbridge was part of the roundabout - so this suggests the HGV was completely out of control, not just a road layout issue?

PS: the footbridge was recently removed...
https://www.dailyecho.co.uk/news/177899 ... e-removed/
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Re: Tightest Curve on a Motorway?

Post by drm567 »

I nominate the off-slips at M1 jn. 6. https://www.google.co.uk/maps/@51.70494 ... 814635,16z The southbound one is particularly daft https://www.google.co.uk/maps/@51.70485 ... 384!8i8192 , look at the tyre marks left by vehicles that have been caught out. To compound the horror just round the bend is a 30 limit and two junctions with residential roads. (It's featured in Chris's site at https://www.roads.org.uk/badjunctions/1-405
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Re: Tightest Curve on a Motorway?

Post by the cheesecake man »

Leeds has a 270 degree turn with 30 limit

Excluding slip roads I thought of the M60 join at Bredbury complete with narrow lanes and 50 limit
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Re: Tightest Curve on a Motorway?

Post by Owain »

JammyDodge wrote: Mon Dec 20, 2021 18:41 I think the A58(M) might have it beat, with this.
The worst thing about that is that the traffic on the slip that you need to turn into is often moving faster than the traffic on the main line, and due to the close proximity of the slip and the main carriageway you can easily mistake which is which if you just glance without looking carefully enough.

And (a separate issue) I've lost count of the number of rear-end shunts I've seen where the slip merges with the motorway just to the left of that shot.
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Re: Tightest Curve on a Motorway?

Post by belgarion »

A lot of these are slip roads etc, but agree with the O.P. the M90 Balmanno Hill, which is made even worse by the fact its around a hill.

This was the cause of a delay to the completion of this section I believe as it was difficult to complete.
It was at the point of the motorway dropping down to the old road during the roadworks when we broke down on one of our holidays in Scotland, my cousin came from Aberdeen with his 3.0L Granada and towed us.

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Re: Tightest Curve on a Motorway?

Post by Unbreakify »

DB124 wrote: Mon Dec 20, 2021 18:17 Not very original, I know.
But, this question comes in two parts:
-Which is the tightest curve on the mainline of a motorway?
-and which is the tightest curve under motorway restrictions?

For the former, my intuition tells me M90 Balmanno Hill or Queensferry, though it is possible that an urban motorway has a sharper curve (A167(M), M4). I haven't included Simister or Worsley because neither were designed as a mainline motorway.

For the latter, a more interesting task is presented. For example, this one west of Newport seems ludicrous. And whoever thought two lanes was a safe idea at Tebay needs to be fired. Is there a cloverleaf loop tighter than these? Or perhaps a really nasty roundabout approach with some awkward corners?

Would love to hear everyone's thoughts and insights on corners with Blue Signs. :)
The M90 is the tightest bend you'll get on a proper motorway, not a slip road.
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JonB2028
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Re: Tightest Curve on a Motorway?

Post by JonB2028 »

Unbreakify wrote: Tue Dec 21, 2021 14:25 The M90 is the tightest bend you'll get on a proper motorway, not a slip road.
The radius of the M90 bend looks to be around 500m. That figures as 510m is one of the tabulated radii in the DMRB - two steps below desirable minimum in current terminology and which used to be termed "limiting" in TD 9/81. I think what pre-dated this was similar, Road note ??

M69 approaching M1 J21 looks to be similar radius as does M11 in Woodford and M5 in West Bromwich. The M90 does look worse, being nearly 180 degrees, though.
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