A3/M25 Wisley Upgrade

[Fluid Dynamics]

I was around the area on Sunday and travelled both ways on the M25 between the M40 and the M3. I have never seen it so quiet during daytime.

I agree - I passed through Wisley on the A3 and it was a ghost town. I haven't seen the queues so short since the roadworks started, and from what I could see the M25 was very unusually quiet too. People clearly decided to just stay home.

As evidenced in LA, every discretionary car journey will have been cancelled - https://www.accessmagazine.org/spring-2 ... le-fizzle/

This is of course used as proof that if you just remove a road all the essential journeys will also be rescheduled to other means which is demonstrably false - no-one has successfully removed a genuinely strategic road (and not an unfinished spur or isolated city centre GSJ) yet. The fabled example in Seoul had numerous alternative motorways adjacent to it.

I travelled up the A3 and onto the M25 on Saturday evening. No queues. Joining the M25 eastbound with the section behind us closed off kinda reminded me of the 1980s before the road was completed, wondering as a child what the soon to be completed section would be like! M25 was quiet but picked up more traffic after Leatherhead. Stopped at Cobham Services which was like a ghost town with most outlets closed. Used the Ionity chargers as we have recently got an electric car and thought there's no better time to try public charging with no-one was around.

[ChrisH]

I was ruminating on this project last week and read Chris' article on Roads.org.uk about it, which included the innovative idea to build half a stack instead of a larger roundabout. It made me wonder how a Dublin M50-esque scheme could complete a full freeflow interchange by re-using the roundabout but making it freeflow by sending the remaining right turns the "wrong" way around it.

The geometry of the turns isn't brilliant but at a 30/40mph speed ought to be manageable.


host image

I'm not familiar with the junction so the NMU links would be separate from this.

[jackal]

I was ruminating on this project last week and read Chris' article on Roads.org.uk about it, which included the innovative idea to build half a stack instead of a larger roundabout. It made me wonder how a Dublin M50-esque scheme could complete a full freeflow interchange by re-using the roundabout but making it freeflow by sending the remaining right turns the "wrong" way around it.

The geometry of the turns isn't brilliant but at a 30/40mph speed ought to be manageable.


host image

I'm not familiar with the junction so the NMU links would be separate from this.

It wouldn't cost much (compared to the high level ramps) to add a bridge on each side so the lower ramps aren't going through an obstacle course.



This is called a stackturbine. A couple of examples in Missouri:

https://www.google.co.uk/maps/@38.63783 ... 495698,15z
https://www.google.co.uk/maps/@38.74469 ... 409224,15z

[ManomayLR]

I was around the area on Sunday and travelled both ways on the M25 between the M40 and the M3. I have never seen it so quiet during daytime.

I agree - I passed through Wisley on the A3 and it was a ghost town. I haven't seen the queues so short since the roadworks started, and from what I could see the M25 was very unusually quiet too. People clearly decided to just stay home.

Interestingly NH is worried that this could become a problem in the future - because everyone followed the guidance and avoided the area this time, people might next time think "oh, my journey will be fine, everyone else will stay home like last time" and if everyone thinks that, well...

I also quoted you, Chris, to say that I read your article on Wisley and it's as usual an extremely informative summary, especially for someone who neither lives near, nor regularly uses, the interchange.

My road enthusiast heart properly ached at the missed opportunity of a Four-Level Stack. If we had started one, then in 2037 or whatever arbitrary time NH have set, we would have been able to complete the stack.

[jackal]

I was around the area on Sunday and travelled both ways on the M25 between the M40 and the M3. I have never seen it so quiet during daytime.

I agree - I passed through Wisley on the A3 and it was a ghost town. I haven't seen the queues so short since the roadworks started, and from what I could see the M25 was very unusually quiet too. People clearly decided to just stay home.

Interestingly NH is worried that this could become a problem in the future - because everyone followed the guidance and avoided the area this time, people might next time think "oh, my journey will be fine, everyone else will stay home like last time" and if everyone thinks that, well...

I also quoted you, Chris, to say that I read your article on Wisley and it's as usual an extremely informative summary, especially for someone who neither lives near, nor regularly uses, the interchange.

My road enthusiast heart properly ached at the missed opportunity of a Four-Level Stack. If we had started one, then in 2037 or whatever arbitrary time NH have set, we would have been able to complete the stack.

The stack they drew up was pretty silly tbh as it was on five levels (i.e. the four new connectors would be built on two levels above the existing three levels).



Option 9 (the half stack) would have delivered the vast majority of the benefit at about half the cost and land take.



If they had built option 9 and later wanted to complete the freeflow - i.e., the scenario you have in mind - there would be more cost effective upgrades than a stack, e.g., have only one fifth level right turn with the other right turn via the roundabout remnant, or alternatively the stackturbine I mention above.

Anyway, the improvement actually being built will surely be swamped by 2037. Freeflow upgrades along the lines of option 9 or the less ambitious option 7 (below) are likely to be revisited down the line.



The improvement being built does at least sort out the A3 and add all four freeflow left turns, which would be fully utilised by upgrades along the lines of option 7 or option 9. So while the scheme is bad it does have more long term value than the likes of M42 J6, M6 J10 or M6 J11 in my view.

[Fluid Dynamics]

I agree - I passed through Wisley on the A3 and it was a ghost town. I haven't seen the queues so short since the roadworks started, and from what I could see the M25 was very unusually quiet too. People clearly decided to just stay home.

Interestingly NH is worried that this could become a problem in the future - because everyone followed the guidance and avoided the area this time, people might next time think "oh, my journey will be fine, everyone else will stay home like last time" and if everyone thinks that, well...

I also quoted you, Chris, to say that I read your article on Wisley and it's as usual an extremely informative summary, especially for someone who neither lives near, nor regularly uses, the interchange.

My road enthusiast heart properly ached at the missed opportunity of a Four-Level Stack. If we had started one, then in 2037 or whatever arbitrary time NH have set, we would have been able to complete the stack.

The stack they drew up was pretty silly tbh as it was on five levels (i.e. the four new connectors would be built on two levels above the existing three levels).



Option 9 (the half stack) would have delivered the vast majority of the benefit at about half the cost and land take.



If they had built option 9 and later wanted to complete the freeflow - i.e., the scenario you have in mind - there would be more cost effective upgrades than a stack, e.g., have only one fifth level right turn with the other right turn via the roundabout remnant, or alternatively the stackturbine I mention above.

Anyway, the improvement actually being built will surely be swamped by 2037. Freeflow upgrades along the lines of option 9 or the less ambitious option 7 (below) are likely to be revisited down the line.



The improvement being built does at least sort out the A3 and add all four freeflow left turns, which would be fully utilised by upgrades along the lines of option 7 or option 9. So while the scheme is bad it does have more long term value than the likes of M42 J6, M6 J10 or M6 J11 in my view.

I broadly agree with your summary, and that the A3 particularly benefits. However, what was missed off this option in my opinion was the addition of south facing slips on the A3 junction at Ockham which means all traffic for Wisley to an from the A3 south will either need to travel through Send and Ripley or go northwards and u-turn at the M25 junction impacting on capacity.

[Chris5156]

I also quoted you, Chris, to say that I read your article on Wisley and it's as usual an extremely informative summary, especially for someone who neither lives near, nor regularly uses, the interchange.

Thank you - it seems to have been quite well received. (One person at the DfT described it as “weirdly well informed”, for which I should credit the level of discussion on SABRE). It’s about ten percent of all my thoughts about the junction but it covers the important stuff!

The stack they drew up was pretty silly tbh as it was on five levels (i.e. the four new connectors would be built on two levels above the existing three levels).

All the options drawn up prior to the consultation were like that, because the whole project was weirdly obsessed with retaining the existing roundabout for NMUs. So the turbine had to be built around the outside, the stack had to go over the top, the new roundabout had to be enormous to cross the M25 either side of the existing bridges. If they hadn’t been insistent on that, the designs they produced might have been quite different, or at least different enough to change the equation around space, environment and affordability.

The ridiculous thing is that they have now provided a new NMU route separate to the roundabout, with a crossing east of the interchange, and I’m no longer convinced that the existing roundabout bridges are going to be retained. I didn’t put this in my blog post because I struggled to find a scheme drawing newer than about 2017 but I did see hints in some of the publicity that the bridges might now have no purpose at all when the project is done. The project signs on the A3, with a CGI rendering of the finished scheme, appear to show the old bridges planted up with trees.

Anyway, the improvement actually being built will surely be swamped by 2037. Freeflow upgrades along the lines of option 9 or the less ambitious option 7 (below) are likely to be revisited down the line.

I don’t know where 2037 came from and I wasn’t able to find out, but it has the strong smell of picking a very modest, achievable goal so your figures look OK.

However, what was missed off this option in my opinion was the addition of south facing slips on the A3 junction at Ockham which means all traffic for Wisley to an from the A3 south will either need to travel through Send and Ripley or go northwards and u-turn at the M25 junction impacting on capacity.

I can’t work out why this wasn’t even considered. It would give Wisley direct access to and from the south, and there’s ample space for the slips. Given that the limited access junction at the other end of the Ripley Bypass is about to have its missing slips added to enable house building, I think it’s only a matter of time before the same is needed there anyway, especially with the development planned on the airfield site. Without the slips, satnavs are bound to route traffic through Ripley instead of u-turning at Wisley. Feels like an easy win that would have been small beer within the budget of a project like this.

[jackal]

The stack they drew up was pretty silly tbh as it was on five levels (i.e. the four new connectors would be built on two levels above the existing three levels).

All the options drawn up prior to the consultation were like that, because the whole project was weirdly obsessed with retaining the existing roundabout for NMUs. So the turbine had to be built around the outside, the stack had to go over the top, the new roundabout had to be enormous to cross the M25 either side of the existing bridges. If they hadn’t been insistent on that, the designs they produced might have been quite different, or at least different enough to change the equation around space, environment and affordability.

I assume they were keeping the bridges to maintain movements during construction.

While that might be reasonable, none of the options involved eventual repurposing of the bridges for a freeflow right turn. For instance, the whirlpool and cyclic options would have four fewer bridges if one of the right turns were via the otherwise unused roundabout bridges, at a reasonable 75m radius - no smaller than the loops on a couple of the options. It would be a bit like this cheap but cheerful Belgian upgrade (which put two "free" freeflow right turns over a fortuitously constructed top level roundabout): https://www.google.co.uk/maps/@50.80078 ... a=!3m1!1e3

That said, I don't think it made any difference as any full freeflow option would have only a modest traffic improvement over option 9 while having much greater cost and landtake - and even option 9 was ultimately considered too much.

The ridiculous thing is that they have now provided a new NMU route separate to the roundabout, with a crossing east of the interchange, and I’m no longer convinced that the existing roundabout bridges are going to be retained. I didn’t put this in my blog post because I struggled to find a scheme drawing newer than about 2017 but I did see hints in some of the publicity that the bridges might now have no purpose at all when the project is done. The project signs on the A3, with a CGI rendering of the finished scheme, appear to show the old bridges planted up with trees.

The 2021 drawings show the bridges over the M25 removed: https://infrastructure.planninginspecto ... %2031).pdf

I don’t know where 2037 came from and I wasn’t able to find out, but it has the strong smell of picking a very modest, achievable goal so your figures look OK.

I think 2037 was treated as 15 years post-opening in the TAR or other early development documents - a standard assumption. Tbf they were quite realistic, noting in the 2016-17 consultation that capacity on some arms of the elongated roundabout would be exceeded by 2037: https://highwaysengland.citizenspace.co ... 0FINAL.pdf

I suspect this will be a forever scheme on SABRE, an itch that we always have to scratch - the opposite of Catthorpe, say, where we talked, it was improved properly and that was the end of the matter (aside from some curiosities with motorway regs).

[ManomayLR]

The stack they drew up was pretty silly tbh as it was on five levels (i.e. the four new connectors would be built on two levels above the existing three levels).

All the options drawn up prior to the consultation were like that, because the whole project was weirdly obsessed with retaining the existing roundabout for NMUs. So the turbine had to be built around the outside, the stack had to go over the top, the new roundabout had to be enormous to cross the M25 either side of the existing bridges. If they hadn’t been insistent on that, the designs they produced might have been quite different, or at least different enough to change the equation around space, environment and affordability.

I assume they were keeping the bridges to maintain movements during construction.

While that might be reasonable, none of the options involved eventual repurposing of the bridges for a freeflow right turn. For instance, the whirlpool and cyclic options would have four fewer bridges if one of the right turns were via the otherwise unused roundabout bridges, at a reasonable 75m radius - no smaller than the loops on a couple of the options. It would be a bit like this cheap but cheerful Belgian upgrade (which put two "free" freeflow right turns over a fortuitously constructed top level roundabout): https://www.google.co.uk/maps/@50.80078 ... a=!3m1!1e3

That said, I don't think it made any difference as any full freeflow option would have only a modest traffic improvement over option 9 while having much greater cost and landtake - and even option 9 was ultimately considered too much.

The ridiculous thing is that they have now provided a new NMU route separate to the roundabout, with a crossing east of the interchange, and I’m no longer convinced that the existing roundabout bridges are going to be retained. I didn’t put this in my blog post because I struggled to find a scheme drawing newer than about 2017 but I did see hints in some of the publicity that the bridges might now have no purpose at all when the project is done. The project signs on the A3, with a CGI rendering of the finished scheme, appear to show the old bridges planted up with trees.

The 2021 drawings show the bridges over the M25 removed: https://infrastructure.planninginspecto ... %2031).pdf

I don’t know where 2037 came from and I wasn’t able to find out, but it has the strong smell of picking a very modest, achievable goal so your figures look OK.

I think 2037 was treated as 15 years post-opening in the TAR or other early development documents - a standard assumption. Tbf they were quite realistic, noting in the 2016-17 consultation that capacity on some arms of the elongated roundabout would be exceeded by 2037: https://highwaysengland.citizenspace.co ... 0FINAL.pdf

I suspect this will be a forever scheme on SABRE, an itch that we always have to scratch - the opposite of Catthorpe, say, where we talked, it was improved properly and that was the end of the matter (aside from some curiosities with motorway regs).

Catthorpe was done well, and now that I think about it, the design is one that would be a Four-Level Stack if designed with all four movements allowed.

For a motorway as busy as the M25 a free-flow junction should have been an absolute certainty, even if not a Four-Level Stack.

[Keiji]

I read the CBRD page a few days ago, and I was really disappointed that it wasn't an April Fools.

The biggest disappointment I have is this:

When you use the junction in future, the sliproad will have two or three lanes - but on three of the four approaches, they will all be for right turns. If you’re going left, on one of those new high speed free-flowing turns they’re building, you will need to take an exit on the left which will appear just before the traffic lights.

(...Actually, studying the diagram closely, it looks to me like all four approaches allocate all the lanes to right turns. I can't see a single approach that dedicates an entire lane to left turns. Maybe I'm just blind, though. I seem to remember seeing it when I previously looked at it...)

As well as, perhaps more importantly, those left-turn sliproads then have to merge with (rather than join) the slips coming off the roundabout.

It ought to be painted with lane 1 being dropped, turning left, and then being gained, in every direction. Lane 2 should meanwhile should be dropped, split into however many oodles of lanes are apparently required to get traffic through some signals, do the right turn, merge back into a single lane, and then be gained as lane 2 on the carriageway.

Yes, of course I'd like to see a fully free-flowing interchange rather than a carbon copy of Simister, but the reason I say this is the biggest disappointment for me is that marking the lanes properly at the time would require precisely £0 extra expenditure.

So, with that said:

The improvement being built does at least sort out the A3 and add all four freeflow left turns, which would be fully utilised by upgrades along the lines of option 7 or option 9. So while the scheme is bad it does have more long term value than the likes of M42 J6, M6 J10 or M6 J11 in my view.

I wouldn't call them "freeflow", because they give way to the traffic coming off the roundabout, as above.

edit:

There is one thing I've noticed which I can be very happy about...

I don't see any of that unnecessary tiger-tailing!

(But it's sad that that is the exception these days rather than the norm...)

[Peter Freeman]

It would be a bit like this cheap but cheerful Belgian upgrade (which put two "free" freeflow right turns over a fortuitously constructed top level roundabout): https://www.google.co.uk/maps/@50.80078 ... a=!3m1!1e3

Digression: interesting. An upgrade more than two decades ago from stackabout (on a smaller scale than Wisley) to 3-level half-stack (on a smaller scale than most UK stacks). I like 'cheap-and-cheerful', as long as it does the job, and doesn't foreclose on future opportunities.

It appears they decided not to accommodate all four long turns - they totally blocked off the roundabout remnants. Two of the turns not required?

The latest GE image shows roadworks have returned in 2023. I wonder what they're doing.

[Bryn666]

It would be a bit like this cheap but cheerful Belgian upgrade (which put two "free" freeflow right turns over a fortuitously constructed top level roundabout): https://www.google.co.uk/maps/@50.80078 ... a=!3m1!1e3

Digression: interesting. An upgrade more than two decades ago from stackabout (on a smaller scale than Wisley) to 3-level half-stack (on a smaller scale than most UK stacks). I like 'cheap-and-cheerful', as long as it does the job, and doesn't foreclose on future opportunities.

It appears they decided not to accommodate all four long turns - they totally blocked off the roundabout remnants. Two of the turns not required?

The latest GE image shows roadworks have returned in 2023. I wonder what they're doing.

The Belgian press are reporting there are defects with the tunnels that are going to cause absolute mayhem from next week - although a very long term aspiration is to fix this interchange properly.

[Peter Freeman]

Ah. That explains the (what appears in GE to be) temporary NE-SW single lane at the ex-roundabout level. So perhaps a problem in the NE-SW tunnel, in the SW-bound direction.

Not so exciting as I might have imagined!

[jackal]

I read the CBRD page a few days ago, and I was really disappointed that it wasn't an April Fools.

The biggest disappointment I have is this:

When you use the junction in future, the sliproad will have two or three lanes - but on three of the four approaches, they will all be for right turns. If you’re going left, on one of those new high speed free-flowing turns they’re building, you will need to take an exit on the left which will appear just before the traffic lights.

(...Actually, studying the diagram closely, it looks to me like all four approaches allocate all the lanes to right turns. I can't see a single approach that dedicates an entire lane to left turns. Maybe I'm just blind, though. I seem to remember seeing it when I previously looked at it...)

As well as, perhaps more importantly, those left-turn sliproads then have to merge with (rather than join) the slips coming off the roundabout.

It ought to be painted with lane 1 being dropped, turning left, and then being gained, in every direction. Lane 2 should meanwhile should be dropped, split into however many oodles of lanes are apparently required to get traffic through some signals, do the right turn, merge back into a single lane, and then be gained as lane 2 on the carriageway.

Yes, of course I'd like to see a fully free-flowing interchange rather than a carbon copy of Simister, but the reason I say this is the biggest disappointment for me is that marking the lanes properly at the time would require precisely £0 extra expenditure.

So, with that said:

The improvement being built does at least sort out the A3 and add all four freeflow left turns, which would be fully utilised by upgrades along the lines of option 7 or option 9. So while the scheme is bad it does have more long term value than the likes of M42 J6, M6 J10 or M6 J11 in my view.

I wouldn't call them "freeflow", because they give way to the traffic coming off the roundabout, as above.

edit:

There is one thing I've noticed which I can be very happy about...

I don't see any of that unnecessary tiger-tailing!

(But it's sad that that is the exception these days rather than the norm...)

I only linked sheets 1-10, covering the junction and A3. There are plenty of oversized tigertails on the sheets covering the M25 merges and diverges: https://infrastructure.planninginspecto ... %2031).pdf These will be modified to account for the smart motorway moratorium, which means a lane drop either side of the junction, but some of the tiger tails may remain.

Btw, there are no give ways for the left turns, and they're all freeflow. Indeed, the only one that isn't a lane gain is A3N to M25E, a lightly used movement. Sheets 1-10 again: https://infrastructure.planninginspecto ... 031%29.pdf

The problem with the left turns is more, as Chris noted, the diverges, which are likely to be blocked by traffic queuing for the rbt.

[B1040]

20+ minutes to do the 2 miles from the A3 services to the interchange yesterday.
Good job I had a good cd.

[jackal]

It would be a bit like this cheap but cheerful Belgian upgrade (which put two "free" freeflow right turns over a fortuitously constructed top level roundabout): https://www.google.co.uk/maps/@50.80078 ... a=!3m1!1e3

Digression: interesting. An upgrade more than two decades ago from stackabout (on a smaller scale than Wisley) to 3-level half-stack (on a smaller scale than most UK stacks). I like 'cheap-and-cheerful', as long as it does the job, and doesn't foreclose on future opportunities.

It appears they decided not to accommodate all four long turns - they totally blocked off the roundabout remnants. Two of the turns not required?

The latest GE image shows roadworks have returned in 2023. I wonder what they're doing.

Step this way: viewtopic.php?p=1334842#p1334842

[John McAdam]

Next closure announced for weekend of 10-12 May (specifically 9pm on Friday 10th to 6am on Monday 13th).

Worth noting however this is for a different stretch to last time - for this weekend the closure is between Junction 9 (A243 Leatherhead) and Junction 10 (A3 Wisley).

[Ritchie333]

Link here

I'll be in Belgium when that happens, so I can give the area a seriously wide berth. However, my parents (who aren't getting any younger) don't live too far from Wisley and I've got this sinking feeling a future I date I go and visit them will clash with a subsequent closure.