M60 Junction 18 Simister Island Interchange

[jackal]

A Preliminary Design Consultation opened today: https://highwaysengland.citizenspace.co ... sultation/

As speculated above, the main change is that M60 J17-18 has been redesigned as D5M with discontinuous hard shoulders (rather than ALR). Otherwise it is the same solid design as before with a freeflow loop for M60 clockwise. The cost estimate is £207 million to £340 million.

[Chris5156]

The cost estimate is £207 million to £340 million.

That’s not a bad price considering it includes a decent length of widening (new hard shoulders!) and new free flow elements. Feels subjectively like better value than the similar-price Wisley scheme.

[jackal]

The cost estimate is £207 million to £340 million.

That’s not a bad price considering it includes a decent length of widening (new hard shoulders!) and new free flow elements. Feels subjectively like better value than the similar-price Wisley scheme.

Indeed, after inflation it's likely to be rather cheaper than Wisley:

Simister Island £273.5m (2023 central estimate)
Wisley £272.6m (2019 funding statement)

And a few more current stackabout upgrades:

M42 Junction 6 £282.3m (2019 funding statement)
M25 junction 28 improvement £124m (2020 funding statement)
Lofthouse £447m (2022 contract pipeline)

The last two would be my favourites, though admittedly they don't include significant mainline improvements

[Peter Freeman]

As speculated above, the main change is that M60 J17-18 has been redesigned as D5M with discontinuous hard shoulders (rather than ALR).

All the design changes make sense, and it remains as one of NH's better efforts.

In particular, simply widening the free-flow left turn at the SW corner to 2 lanes without a shoulder is eminently pragmatic and welcome.

However, building new J17-18 hard shoulders is surprising. Since this project is unlikely to be properly underway before the ALR moratorium and review is completed, I would have expected simply a deferral of that widening, pending the final outcome. This looks rather like they anticipate the outcome to be 'no new ALR'.

I suppose they could scrub the shoulders at the last minute, if the outcome is ALR-favourable.

[Chris5156]

However, building new J17-18 hard shoulders is surprising. Since this project is unlikely to be properly underway before the ALR moratorium and review is completed, I would have expected simply a deferral of that widening, pending the final outcome. This looks rather like they anticipate the outcome to be 'no new ALR'.

I expect the widening is considered critical to the project - the eastbound diverge will be closer to J17, which will exacerbate weaving problems, and some widening will be needed simply to extend the merge and diverge lengths for the upgraded sliproads. Disconnecting it from the project in the hope of doing it later would probably set it back to a future RIS and add years to the timeline.

If the cost of some intermittent hard shoulder can be accommodated within the project budget, then this is the pragmatic solution: the outcome of the ATM moratorium is unknown, so adding a bit of hard shoulder guarantees this project can go ahead no matter what.

[jackal]

Also it's five lane, which as far as I know was never approved for ALR in any case. Maybe their workaround was to think of it as four lane ALR plus long auxiliary lanes, or maybe they just hadn't noticed that GD 301 doesn't talk about five lane ALR.

In any case, as five lane ALR was dubious even when ALR was generally allowed, it is perfectly sensible to provide hard shoulders instead. And there's presumably a higher risk of a breakdown on a road that's busy enough for five lanes, so the HS becomes more cost effective.

[jackal]

The traffic modelling report contains some useful information, e.g.:

Most turn counts for 2042 "do something" (i.e., with the loop) can be calculated from the second plate, and you can estimate the rest if you assume that movements in opposite directions are similar (shown in bold):

-------M66N M62E M60S M60W
M66N -- 7 39 19
M62E 7 -- 10 69
M60S 35 10 -- 31
M60W 19 66 31 --

(AADT in thousands. N means north, not northbound.)

So here are the movement pairs in order:

1. M60/M62 mainline - 66-69k
2. M60/M66 mainline - 35-39k
3. M60W to/from M60S - 31k
4. M60W to/from M66 - 19k
5. M62 to/from M60S - 10k
6. M62 to/from M66 - 7k

[jackal]

An update in local press indicates a DCO application in the winter. The scheme page indicates construction would start in 2025 - there's also an interim report on the most recent consultation.

https://www.burytimes.co.uk/news/237121 ... nge-plans/
https://nationalhighways.co.uk/our-road ... terchange/

[jackal]

The DCO application was made last week (2 April): https://national-infrastructure-consent ... s/TR010064

[Keiji]

I'm late to the party here, but it's a real shame to see either of these bad options being built. It's confusing, sprawling, and subjectively ugly - a main carriageway should never be sent around what is effectively a 360 degree loop like that. In my totally unprofessional armchair opinion, even "do nothing" would have been better.

I really do think they should have just done this:

Another, cheaper solution, which could be used. Removing the M60 turning traffic from the roundabout

J18-2.jpg

Yes, there's this small issue:

The problem with the original plan is that it puts the new slips much closer to J17. It's essentially an additional limited access junction to the west of the existing one. Already the weaving situation is very bad.

But this can easily be fixed by connecting the J17 slips directly to the Simister roundabout, rather than onto the short length of main carriageway between the two. I think the cost of forcing any east-facing J17 traffic to use the Simister roundabout is worth it for the benefit of removing M60 through traffic from said roundabout - plus, there's precedent, as this kind of arrangement is already used successfully in lots of places in this country.

[Big L]

… a main carriageway should never be sent around what is effectively a 360 degree loop like that…

*nearer 270 degrees.

Unless there’s a daredevil loop-the-loop in the plans I’ve missed. Would be a good time to use minimum speed limit signs!

[Phil]

I'm late to the party here, but it's a real shame to see either of these bad options being built. It's confusing, sprawling, and subjectively ugly - a main carriageway should never be sent around what is effectively a 360 degree loop like that. In my totally unprofessional armchair opinion, even "do nothing" would have been better.

I suggest you stop being fixated on road numbers and have a look at the traffic volumes quoted above.

Using those it’s clear the busiest movements by a very long way are M60 - M62 and M66 - M60. The fact that the motorway numbers change makes zero difference!

Therefore it’s clear that in traffic terms, sending M60 - M60 traffic through a looped slip road is actually the best solution for the majority of motorists.

[Keiji]

… a main carriageway should never be sent around what is effectively a 360 degree loop like that…

*nearer 270 degrees.

Unless there’s a daredevil loop-the-loop in the plans I’ve missed. Would be a good time to use minimum speed limit signs!

Looking at the M60 as a ring, staying on the M60 is straight on, and therefore any loop that goes from M60 clockwise to M60 clockwise can feel like a 360 degree loop even if on the ground it's only 270 degrees. And if you consider a longer stretch of road rather than just Simister itself, you can see the missing 90 degrees where the main carriageway bends left at J17 and J19.

I'm late to the party here, but it's a real shame to see either of these bad options being built. It's confusing, sprawling, and subjectively ugly - a main carriageway should never be sent around what is effectively a 360 degree loop like that. In my totally unprofessional armchair opinion, even "do nothing" would have been better.

I suggest you stop being fixated on road numbers and have a look at the traffic volumes quoted above.

Using those it’s clear the busiest movements by a very long way are M60 - M62 and M66 - M60. The fact that the motorway numbers change makes zero difference!

Therefore it’s clear that in traffic terms, sending M60 - M60 traffic through a looped slip road is actually the best solution for the majority of motorists.

I suspect there is an element of induced demand here. People could easily be choosing to avoid the M60 - M60 movement simply because it's difficult to perform (relative to just going straight on) and doesn't have the necessary capacity in the first place. If, for example, Simister had been using the "southerly bypass" design, from the moment the M60 ring was originally completed, I would expect the traffic volumes by now would have developed rather more in favor of M60 - M60.

M60 - M62 makes sense because it's the major east-west route. Of course there has been that argument for pulling this out onto a separate pair of carriageways, totally separate from the M60 ring, so without that it would be a lot lower. As for M66 - M60, I'm not sure since I'm not local - but it looks like this could also be explained by induced demand, i.e. it has built up as a commuter route just by being so (relatively) convenient.

So it may well be the best solution for the majority of today's motorists, but that doesn't make it the ideal long-term solution, it will just help cement today's patterns more in the future.

Anyway, that's just my thinking. I certainly should have worded that first line of my previous post more carefully, so I'm sorry about the excessive negativity there (I've had a stressful day, tried to while away the evening checking various websites instead of doing something more productive, and naturally as a result, found something to criticise) - but I still dislike the solution they went for.

[Bryn666]

The majority of traffic is using the M60 to M62 line - no-one is driving laps of the M60 except roadgeeks and they're not deterred by the presence of J18 anyway. The loop proposal is fine, it is not confusing, and it reflects reality.

The direct slips you show would require significant demolition between J18 and J17 to fit everything in, including an overbridge, several houses, and potentially several 275kV towers. Complete non-starter just for those reasons I am afraid.

[Patrick Harper]

The loop is good but the widening westbound seems risky to me, maybe they've modelled it and determined that weaving here wouldn't jeopardise the capacity benefit?

[Big L]

… a main carriageway should never be sent around what is effectively a 360 degree loop like that…

*nearer 270 degrees.

Unless there’s a daredevil loop-the-loop in the plans I’ve missed. Would be a good time to use minimum speed limit signs!

Looking at the M60 as a ring, staying on the M60 is straight on, and therefore any loop that goes from M60 clockwise to M60 clockwise can feel like a 360 degree loop even if on the ground it's only 270 degrees. And if you consider a longer stretch of road rather than just Simister itself, you can see the missing 90 degrees where the main carriageway bends left at J17 and J19.
…

I can’t help point out that the entire M60 is a 360 degree loop. Maybe the whole motorway should have been built straight to avoid confusion.

[jackal]

I'm late to the party here, but it's a real shame to see either of these bad options being built. It's confusing, sprawling, and subjectively ugly - a main carriageway should never be sent around what is effectively a 360 degree loop like that. In my totally unprofessional armchair opinion, even "do nothing" would have been better.

So congested signals are better than freeflow? I guess Tarbock Island was better before the upgrade? Really struggling to get my head around this one...

Btw, I consider this to be a compact and aesthetically pleasing design. It's bizarre you claim it's sprawling while proposing something with much higher land take.

I really do think they should have just done this:

Another, cheaper solution, which could be used. Removing the M60 turning traffic from the roundabout

J18-2.jpg

Completely impractical due to the level of demolition, not to mention the primary school with motorways encroaching on two sides.

Also it would perform worse due to the mismatch with traffic flows.

… a main carriageway should never be sent around what is effectively a 360 degree loop like that…

*nearer 270 degrees.

Unless there’s a daredevil loop-the-loop in the plans I’ve missed. Would be a good time to use minimum speed limit signs!

Looking at the M60 as a ring, staying on the M60 is straight on, and therefore any loop that goes from M60 clockwise to M60 clockwise can feel like a 360 degree loop even if on the ground it's only 270 degrees. And if you consider a longer stretch of road rather than just Simister itself, you can see the missing 90 degrees where the main carriageway bends left at J17 and J19.

I'm late to the party here, but it's a real shame to see either of these bad options being built. It's confusing, sprawling, and subjectively ugly - a main carriageway should never be sent around what is effectively a 360 degree loop like that. In my totally unprofessional armchair opinion, even "do nothing" would have been better.

I suggest you stop being fixated on road numbers and have a look at the traffic volumes quoted above.

Using those it’s clear the busiest movements by a very long way are M60 - M62 and M66 - M60. The fact that the motorway numbers change makes zero difference!

Therefore it’s clear that in traffic terms, sending M60 - M60 traffic through a looped slip road is actually the best solution for the majority of motorists.

I suspect there is an element of induced demand here. People could easily be choosing to avoid the M60 - M60 movement simply because it's difficult to perform (relative to just going straight on) and doesn't have the necessary capacity in the first place. If, for example, Simister had been using the "southerly bypass" design, from the moment the M60 ring was originally completed, I would expect the traffic volumes by now would have developed rather more in favor of M60 - M60.

"How things might have been" is irrelevant. All that matters is what the flows would be under the various options. And clearly, given M60-M62 has more than twice the traffic of M60-M60, it will still have more post-upgrade and should retain the mainline. National Highways are rightly in the business of serving people, not road numbers.

[nowster]

Of course if things had been different this wouldn't have been needed.

https://pathetic.org.uk/unbuilt/m62_relief_road/ (With the obligatory "Sheesh!" when linking there.)

[Bryn666]

Of course if things had been different this wouldn't have been needed.

https://pathetic.org.uk/unbuilt/m62_relief_road/ (With the obligatory "Sheesh!" when linking there.)

You'd still have had the issues of the right turns at Simister even with the relief road. Movements between the then M62 and M66 towards Rhodes were always going to be free-flow at some stage under these plans.

[M64]

A few things that I have noted looking at the general arrangement plans dated July 2023 on the NH website linked above (the formal as per DCO submission documents are not viewable yet)

• No surprises but hard shoulders are generally provided where possible (i.e. except at major constraints such as existing bridges or requiring property demolition)

• The M60 c/w right turn (using the loop) is the first exit, the left turn to M66 is the second exit, this seems quite unusual and somewhat counter-intuitive, I can't think of another free-flow interchange in the UK where the right turn turn is on the left (first exit)? (No doubt others will think of some now I've written this)

• There is quite a substantial realignment of the central reserve on the M60(S)<>M66(N) through the junction to allow for the 2 lanes NB and 4 lanes SB (no hardshoulders)

• The residual segregated left-turn lanes (SLTL) seem a bit odd, for example M62 to M60 c/w you leave the exit slip on a SLTL and then have a free-flow merge onto the M60, and the M60c/w to M66 you have a free flow slip road going into quite a tight left-turn SLTL (seems very tight if it is considered to be a free-flow link that isn't a loop)

• The M60 ac/w left turn is a two-lane SLTL which is not permitted in the DMRB