A3/M25 Wisley Upgrade

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fras
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Re: A3/M25 Wisley Upgrade

Post by fras » Wed Jan 13, 2021 13:01

BF2142 wrote:
Wed Jan 13, 2021 12:46
JohnA14J50 wrote:
Tue Jan 12, 2021 15:27
Not a user of this junction...how will making the roundabout bigger remotely help when it's clear the layout is not suitable?
Haha, roundabout used as a motorway to DC junction on nation's busiest road...what a stunning example of crap British sub-engineering. Save the money and build a free-flowing, high-speed interchange.
Well, that's because we have development by spatchcock now, where no long term planning is done, its all fire-fighting schemes. Of course lack of dosh over the last 30 years has meant that realistically, I suppose that's all the poor old highways engineers can really do.

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Re: A3/M25 Wisley Upgrade

Post by SteveA30 » Wed Jan 13, 2021 17:00

It isn't that long since Catthorpe was corrected, have things changed financially and planning wise since then? HE are normally quite keen on free-flow left turns, that also seems to have gone out of the window.
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jackal
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Re: A3/M25 Wisley Upgrade

Post by jackal » Wed Jan 13, 2021 17:05

SteveA30 wrote:
Wed Jan 13, 2021 17:00
HE are normally quite keen on free-flow left turns, that also seems to have gone out of the window.
^This very scheme adds four freeflow left turns, whatever its other failings.
fras wrote:
Wed Jan 13, 2021 13:01
BF2142 wrote:
Wed Jan 13, 2021 12:46
JohnA14J50 wrote:
Tue Jan 12, 2021 15:27
Not a user of this junction...how will making the roundabout bigger remotely help when it's clear the layout is not suitable?
Haha, roundabout used as a motorway to DC junction on nation's busiest road...what a stunning example of crap British sub-engineering. Save the money and build a free-flowing, high-speed interchange.
Well, that's because we have development by spatchcock now, where no long term planning is done, its all fire-fighting schemes. Of course lack of dosh over the last 30 years has meant that realistically, I suppose that's all the poor old highways engineers can really do.
Not really applicable for a scheme like this, though, is it. HE/DfT literally told the engineers to come up with a freeflowing all movements junction, with budget to match, but they designed a bigger roundabout instead. See also M42 J6.

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Vierwielen
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Re: A3/M25 Wisley Upgrade

Post by Vierwielen » Thu Jan 14, 2021 18:01

jackal wrote:
Wed Jan 13, 2021 17:05
SteveA30 wrote:
Wed Jan 13, 2021 17:00
HE are normally quite keen on free-flow left turns, that also seems to have gone out of the window.
^This very scheme adds four freeflow left turns, whatever its other failings.
fras wrote:
Wed Jan 13, 2021 13:01
BF2142 wrote:
Wed Jan 13, 2021 12:46


Haha, roundabout used as a motorway to DC junction on nation's busiest road...what a stunning example of crap British sub-engineering. Save the money and build a free-flowing, high-speed interchange.
Well, that's because we have development by spatchcock now, where no long term planning is done, its all fire-fighting schemes. Of course lack of dosh over the last 30 years has meant that realistically, I suppose that's all the poor old highways engineers can really do.
Not really applicable for a scheme like this, though, is it. HE/DfT literally told the engineers to come up with a freeflowing all movements junction, with budget to match, but they designed a bigger roundabout instead. See also M42 J6.
:pig: :pig: :pig:

marconaf
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Re: A3/M25 Wisley Upgrade

Post by marconaf » Thu Jan 21, 2021 22:15

It is very disapointing that this bottleneck which I’ve used in various directions for years - is going to endure even worse congestion whilst it is turned into something only slighlty less worse.

Any chance this will get re-cast? The A3 South to M25 West desperately needs a freeflow - it stacks up past the previous A3 junction at peak so unless this scheme gives truly vast stacking space (and the existing one isnt too cramped to start with), it is almost a complete waste of effort.

Hell, if its minimum effort just do LH turn lanes and widen the A3 South off slip to segregate M25 east and roundabout trafficz

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Re: A3/M25 Wisley Upgrade

Post by BF2142 » Fri Jan 22, 2021 12:56

jackal wrote:
Wed Jan 13, 2021 17:05
SteveA30 wrote:
Wed Jan 13, 2021 17:00
HE are normally quite keen on free-flow left turns, that also seems to have gone out of the window.
^This very scheme adds four freeflow left turns, whatever its other failings.
fras wrote:
Wed Jan 13, 2021 13:01
BF2142 wrote:
Wed Jan 13, 2021 12:46


Haha, roundabout used as a motorway to DC junction on nation's busiest road...what a stunning example of crap British sub-engineering. Save the money and build a free-flowing, high-speed interchange.
Well, that's because we have development by spatchcock now, where no long term planning is done, its all fire-fighting schemes. Of course lack of dosh over the last 30 years has meant that realistically, I suppose that's all the poor old highways engineers can really do.
Not really applicable for a scheme like this, though, is it. HE/DfT literally told the engineers to come up with a freeflowing all movements junction, with budget to match, but they designed a bigger roundabout instead. See also M42 J6.
Then my question is: why weren't the engineers told "no", go and design a free-flow junction per the brief? Are they not taught how to design this stuff any more? Because it sounds like they only have one trick up their sleeve, which is variations on a roundabout. It's like they've lost all institutional and technical knowledge of building major interchanges.

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Bryn666
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Re: A3/M25 Wisley Upgrade

Post by Bryn666 » Fri Jan 22, 2021 14:36

BF2142 wrote:
Fri Jan 22, 2021 12:56
jackal wrote:
Wed Jan 13, 2021 17:05
SteveA30 wrote:
Wed Jan 13, 2021 17:00
HE are normally quite keen on free-flow left turns, that also seems to have gone out of the window.
^This very scheme adds four freeflow left turns, whatever its other failings.
fras wrote:
Wed Jan 13, 2021 13:01

Well, that's because we have development by spatchcock now, where no long term planning is done, its all fire-fighting schemes. Of course lack of dosh over the last 30 years has meant that realistically, I suppose that's all the poor old highways engineers can really do.
Not really applicable for a scheme like this, though, is it. HE/DfT literally told the engineers to come up with a freeflowing all movements junction, with budget to match, but they designed a bigger roundabout instead. See also M42 J6.
Then my question is: why weren't the engineers told "no", go and design a free-flow junction per the brief? Are they not taught how to design this stuff any more? Because it sounds like they only have one trick up their sleeve, which is variations on a roundabout. It's like they've lost all institutional and technical knowledge of building major interchanges.
The standards have been so over specified and gold plated that free-flowing interchanges are nigh on impossible to design now. Curve radii, superelevation, forward stopping sight distance, etc, they pretty much rule out the compact and staggeringly complicated things France, the US, and Spain to name just three, come up with. Signalised roundabouts are much more straightforward.
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Stevie D
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Re: A3/M25 Wisley Upgrade

Post by Stevie D » Fri Jan 22, 2021 14:51

Bryn666 wrote:
Fri Jan 22, 2021 14:36
The standards have been so over specified and gold plated that free-flowing interchanges are nigh on impossible to design now. Curve radii, superelevation, forward stopping sight distance, etc, they pretty much rule out the compact and staggeringly complicated things France, the US, and Spain to name just three, come up with. Signalised roundabouts are much more straightforward.
Although when you see what has been done, it is sometimes questionable.
One that springs to mind is the M62 eastbound to A1(M) northbound curve at New Ferrybridge. The angle and elevation means that you can't see what's coming on the sliproad from the westbound side until you're almost at the merge line, and you then have a very short taper to merge in. The sensible thing IMO would have been to have traffic from the westbound carriageway into one lane at this point and then have a lane gain on the sliproad rather than traffic from the eastbound carriageway having to merge/give way. Although there is a 50mph limit on the sliproads it is poorly observed because drivers don't see the need for it – the curvature and forwards visibility is absolutely fine for 70 in a car there, and it isn't obvious that drivers joining the slip road can't see you coming until the last second.

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Bryn666
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Re: A3/M25 Wisley Upgrade

Post by Bryn666 » Fri Jan 22, 2021 15:01

Stevie D wrote:
Fri Jan 22, 2021 14:51
Bryn666 wrote:
Fri Jan 22, 2021 14:36
The standards have been so over specified and gold plated that free-flowing interchanges are nigh on impossible to design now. Curve radii, superelevation, forward stopping sight distance, etc, they pretty much rule out the compact and staggeringly complicated things France, the US, and Spain to name just three, come up with. Signalised roundabouts are much more straightforward.
Although when you see what has been done, it is sometimes questionable.
One that springs to mind is the M62 eastbound to A1(M) northbound curve at New Ferrybridge. The angle and elevation means that you can't see what's coming on the sliproad from the westbound side until you're almost at the merge line, and you then have a very short taper to merge in. The sensible thing IMO would have been to have traffic from the westbound carriageway into one lane at this point and then have a lane gain on the sliproad rather than traffic from the eastbound carriageway having to merge/give way. Although there is a 50mph limit on the sliproads it is poorly observed because drivers don't see the need for it – the curvature and forwards visibility is absolutely fine for 70 in a car there, and it isn't obvious that drivers joining the slip road can't see you coming until the last second.
That taper merge is designed for "80km/h", which totally ignores the real world speeds of traffic using a motorway to motorway interchange hence why it feels wrong. As you say, a lane gain would have made sense from a traffic management point of view but you can't have that because the standards are so rigid about merge types.

It's just ridiculous, I don't know who wrote it and what they were aiming for, but all this "look how smart we are" has actually made motorways harder to use for an ordinary driver, and we wonder why driver quality falls through the floor.
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JammyDodge
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Re: A3/M25 Wisley Upgrade

Post by JammyDodge » Fri Jan 22, 2021 15:45

If they wanted to reduce cost, couldn't they just build a freeflow between the M25 and A3 South, leaving the existing roundabout to handle London traffic?

Edit: Spelling
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Chris5156
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Re: A3/M25 Wisley Upgrade

Post by Chris5156 » Fri Jan 22, 2021 16:03

JammyDodge wrote:
Fri Jan 22, 2021 15:45
If they wanted to reduce cost, couldn't they just build a freeflow between the M25 and A3 South, leaving the existing roundabout to handle London traffic?

Edit: Spelling
That would require the two right turns to cross each other, meaning two extra levels to the junction or a space-hungry loop. This is why, in all the options for adding just two right turns and not all four, the proposal was to add two opposite right turns, avoiding the need for them to cross, and making the junction cheaper.

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Re: A3/M25 Wisley Upgrade

Post by marconaf » Fri Jan 22, 2021 16:08

Chris5156 wrote:
Fri Jan 22, 2021 16:03
JammyDodge wrote:
Fri Jan 22, 2021 15:45
If they wanted to reduce cost, couldn't they just build a freeflow between the M25 and A3 South, leaving the existing roundabout to handle London traffic?

Edit: Spelling
That would require the two right turns to cross each other, meaning two extra levels to the junction or a space-hungry loop. This is why, in all the options for adding just two right turns and not all four, the proposal was to add two opposite right turns, avoiding the need for them to cross, and making the junction cheaper.
Or just one level for one right turn - the roundabout then having capacity to handle the other.

Not sure if A3 south to M25 west or M25 east or A3 south would be the larger. I think the former.

An M40/M25 type would be ideal, I wonder which actually has the more traffic.

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Re: A3/M25 Wisley Upgrade

Post by JammyDodge » Fri Jan 22, 2021 16:45

Chris5156 wrote:
Fri Jan 22, 2021 16:03
JammyDodge wrote:
Fri Jan 22, 2021 15:45
If they wanted to reduce cost, couldn't they just build a freeflow between the M25 and A3 South, leaving the existing roundabout to handle London traffic?

Edit: Spelling
That would require the two right turns to cross each other, meaning two extra levels to the junction or a space-hungry loop. This is why, in all the options for adding just two right turns and not all four, the proposal was to add two opposite right turns, avoiding the need for them to cross, and making the junction cheaper.
Yes, you would add 2 more level, and I get you point, more height costs a lot more
I included an MS Paint drawing to show my example
Screenshot 2021-01-22 163929-min.jpg
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jackal
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Re: A3/M25 Wisley Upgrade

Post by jackal » Fri Jan 22, 2021 17:24

Volumes are similar for 6/8 turning movements. A3 North to/from M25 East is much lower (which is obvious when you look at a map).

M25 A3 - Copy.PNG

As mentioned above, for options with two freeflow rights turns they only looked at options with rights turns for opposite movements (so they don't have to cross each other on a fifth level). These were options 9 and 10. They also looked at two options with a single right turn freeflow for M25W to A3S - options 7 and 8.

Wisley long list.PNG

Of these options 8, 9 and 10 made it through to the options workshop.

Options workshop scores.PNG

Option 9 made it to consultation, proved the most popular option, but HE rejected it because they love big pointless roundabouts.

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jackal
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Re: A3/M25 Wisley Upgrade

Post by jackal » Fri Jan 22, 2021 17:28

Drawings of options with 1-2 freeflow rights turns:

7 - Copy.jpg
9 - Copy.jpg
10 - Copy.jpg

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Re: A3/M25 Wisley Upgrade

Post by Micro The Maniac » Fri Jan 22, 2021 18:00

marconaf wrote:
Fri Jan 22, 2021 16:08
Not sure if A3 south to M25 west or M25 east or A3 south would be the larger. I think the former.
Am I the only one having to do mental gymnastics to work out which way M25(E) and M25(W) is here :roll:

I think
  • M25(W) is clockwise (or north) - ie to Heathrow, and
  • M25(E) is anti-clockwise (or south) - ie towards Gatwick

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Re: A3/M25 Wisley Upgrade

Post by Vierwielen » Fri Jan 22, 2021 18:21

Micro The Maniac wrote:
Fri Jan 22, 2021 18:00
marconaf wrote:
Fri Jan 22, 2021 16:08
Not sure if A3 south to M25 west or M25 east or A3 south would be the larger. I think the former.
Am I the only one having to do mental gymnastics to work out which way M25(E) and M25(W) is here :roll:

I think
  • M25(W) is clockwise (or north) - ie to Heathrow, and
  • M25(E) is anti-clockwise (or south) - ie towards Gatwick
Whenever I use that junction, I feel that the M25 should be signposted M25(N) and M25 (SE) and that the A3 should be signposted A3(SW) and A3(NE).

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Re: A3/M25 Wisley Upgrade

Post by marconaf » Fri Jan 22, 2021 18:31

jackal wrote:
Fri Jan 22, 2021 17:24
Really interesting data.

The right hand turns are:

A3 south to M25 west - 1550
M25 west to A3 south - 1010
M25 east to A3 north - 498
A3 north to M25 east - 378

So the biggies are the two I suggested, of which the A3 south is 50% larger as I thought. So the option with freeflow for that alone seems a clear winner as that would leave the roundabout free to accomodate the others. Throw in left turns to cut those bits out of the roundabout and job done!

As proposal 7 basically. Seems odd that didnt go through - the others do have huge land take.

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Re: A3/M25 Wisley Upgrade

Post by marconaf » Fri Jan 22, 2021 18:35

The compass point isnt entirely unreasonable but it does fairly well represent the cardinal directions, A3 north is going north into london, south towards the coast whilst M25 is going to the west of london and towards eastern half of the region so it seems ok.

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