A3/M25 Wisley Upgrade

[firefly]

If the proposed development at the old Wisley Airfield site ever happens, then it would be quite logical to expect that people may certainly cycle (less likely walk or use a horse) to Byfleet or Cobham from there, and would need some way to cross the M25, so maintaining a safe crossing is really just futureproofing

No, it is not futureproofing, it is actually rather idiotic. To get pedestrians, cyclists and horse riders to the retained roundabout one needs to build subways or bridges across the link roads of the new junction. And all this only to make use of a then obsolete piece of infrastructure which is over-dimensioned for this purpose and which will still maintenance. For these costs one could get a new bridleway with a cheaper to maintain bridge over the M25 offside the junction.

[jackal]

The local traffic is presumably that on Old Lane from Effingham, and on Wisley Lane.

No it isn't. Under all options the entry from Wisley Lane will be stopped up, with a service road to the next junction west. Old Lane is also stopped up under option 16:

Old Lane (A3 southbound between J10 and Ockham Junction) would be stopped up in
Option 16 and traffic re-routed via the local road network. In Option 9 and 14, Old Lane
junction with the Junction 10 slip road is maintained.

https://highwaysengland.citizenspace.co ... 5J10A3.pdf

[mnb20]

What other local traffic is there then? There was talk of using the roundabout for "local traffic" and if that's not Old Lane and Wisley Lane, who is it? Everyone else will be on the A3 to/from at least the next major junction so won't need any special facilities here.

[jackal]

What other local traffic is there then? There was talk of using the roundabout for "local traffic" and if that's not Old Lane and Wisley Lane, who is it? Everyone else will be on the A3 to/from at least the next major junction so won't need any special facilities here.

The best explanation is that the brochure is in error on that point.

[Glom]

There's a silent YouTube video out.

Lets be honestm 24 months work to build a bigger roundabout would be pretty embarrassing.

[jackal]

There's a silent YouTube video out.

Lets be honestm 24 months work to build a bigger roundabout would be pretty embarrassing.

And a snip at £150m!

The one thing I like about the elongated roundabout option is that it proves that building new bridges adjacent to the existing bridges, and over the existing slips, is feasible:

https://youtu.be/R8Xt2QE-_4E?t=232

Of course, I want to do that so we can fit in two freeflow ramps at that level, like this:

[si404]

Of course, I want to do that so we can fit in two freeflow ramp at that level, like this:

Option 9 final.jpg

Definitely a decent 'phase 2', keeping one of the original roundabout bridges for the non-motorised traffic (such as it is).

[A320Driver]

That's a great plan, jackal. Submit it to HE!

[ais523]

I'm worried about how the two new bridges cross each other in that plan. There's going to have to be a pretty rapid change in elevation to fit one over the other.

I think probably the better upgrade path here is to start off with option 9, and if/when it can't cope, use the level currently occupied by the roundabout in order to upgrade the junction to a four level stack. (Sadly, reusing the roundabout bridges themselves probably wouldn't be possible because the slip road wouldn't be straight enough to take at speed.)

However, option 9, possibly with freeflow lefts added, should take most of the traffic away from the roundabout, meaning that the remaining traffic will have an easier time of using it to turn right. So it's possible that the further upgrade won't be needed.

Incidentally, I'm beginning to suspect that it's a good idea to build stackabouts larger than originally seems necessary so that there's more room to upgrade. If there's room to fit sliproads inside the roundabout, it gives you many more options for upgrade paths. With a small one like this, the roundabout pretty much has to be ignored in any upgrade.

[Vierwielen]

I'm worried about how the two new bridges cross each other in that plan. There's going to have to be a pretty rapid change in elevation to fit one over the other.

As I suggested earlier, is it not possible to replace these bridges with tunnels under the M25. This will remove the need for the massive embankments that have been proposed.

[jackal]

I'm worried about how the two new bridges cross each other in that plan.There's going to have to be a pretty rapid change in elevation to fit one over the other.

The new bridges don't cross, or even come close to each other. They cross the realigned M25 offslips. That part of the slips is obviously lower than the level of the roundabout, because they connect to the M25 (which goes under the roundabout). This accounts for part of the elevation change. The rest can be achieved simply by making the new bridges gently rise before they cross the M25 offslips.

I think probably the better upgrade path here is to start off with option 9, and if/when it can't cope, use the level currently occupied by the roundabout in order to upgrade the junction to a four level stack. (Sadly, reusing the roundabout bridges themselves probably wouldn't be possible because the slip road wouldn't be straight enough to take at speed.)

This is the tight space you're talking about putting two skewed direct connectors through - and you have to somehow do that without disrupting either mainline or the roundabout that encircles your construction site! It's no surprise that the stack (option 18) was rated 2 for feasibility, compared to 8 for the cyclic design.

[mapboy]

Given the two options we have left available, I would certainly choose option 9. Enlarging the roundabout will only serve to delay a more substantial rebuild into the future where as the former option goes some way to fully reconstructing the junction. By removing those major flows the roundabout itself should become far more efficient at dealing with the remaining movements; also providing potential provision for an upgrade to a four-level stack as and when needed.

I also spent the morning churning out some maps to go on the wiki page.

[jackal]

Nice work!

Given the two options we have left available, I would certainly choose option 9. Enlarging the roundabout will only serve to delay a more substantial rebuild into the future where as the former option goes some way to fully reconstructing the junction.

Option 14 is worse than nothing in terms of a future rebuild, as the new bridges would be extra stuff to work around or demolish. £150m to essentially go backwards in the long term.

By removing those major flows the roundabout itself should become far more efficient at dealing with the remaining movements; also providing potential provision for an upgrade to a four-level stack as and when needed.

As sniffy as many (including myself) have been about the failure to provide full freeflow, option 9 is nevertheless an excellent improvement, and even provides greater time savings than option 16 by the design year of 2037 as its ramps are more direct.

[mapboy]

Option 14 is worse than nothing in terms of a future rebuild, as the new bridges would be extra stuff to work around or demolish. £150m to essentially go backwards in the long term.

Indeed, I've just replied to the consultation an made it clear in my response that option 14 is essentially a waste of money for those reasons.

[Chris5156]

I also spent the morning churning out some maps to go on the wiki page.

These are great! I have to be slightly pedantic, though - I don't believe the roundabout would remain with full access to all routes in option 16, rather the bridges across the M25 would remain for footways/cycle paths/horse riding along the line of the A3.

[mapboy]

I also spent the morning churning out some maps to go on the wiki page.

These are great! I have to be slightly pedantic, though - I don't believe the roundabout would remain with full access to all routes in option 16, rather the bridges across the M25 would remain for footways/cycle paths/horse riding along the line of the A3.

I have no problem with pedantry! I was rather confused from reading the consultation whether it would remain connected or not. I'll try to get an uploaded revision later.

[jackal]

You can find more detailed plans towards the back of the TAR: https://highwaysengland.citizenspace.co ... 5J10A3.pdf

[Johnathan404]

This is what I had in mind. It would be politically difficult, but hopefully build-able and future-proofed. My scale might be out - it's hard to draw a decent GSJ on top of a roundabout.

I've marked a LAR and two maintenance roads to fulfil the requirement that every road user and every movement be accounted for... I don't think they are particularly important. If built, I would expect all movements to have a mandatory 50mph speed limit, but I'd rather just have warning signs.

[jackal]

Consultation closes in five days: https://highwaysengland.citizenspace.co ... provement/

[Duncan]

This is what I had in mind. It would be politically difficult, but hopefully build-able and future-proofed. My scale might be out - it's hard to draw a decent GSJ on top of a roundabout.

I've marked a LAR and two maintenance roads to fulfil the requirement that every road user and every movement be accounted for... I don't think they are particularly important. If built, I would expect all movements to have a mandatory 50mph speed limit, but I'd rather just have warning signs.a3.jpg

Johnny, have you kept the A3 mainline going through the junction as now? I can't tell whether your green lines are the LAR or whether you are diverting the road. Speaking of local access, Heyswood Guide Camp has a direct access onto the A3 just before the junction. I presume this, plus the Hilton Hotel and the former San Domenico Restaurant, means that while the section from Painshill to Esher Common is part of the Esher Bypass, Painshill to Wisley is the old road. Is one of the slip roads at Painshill the old road, or was it covered up when Cobham was bypassed?