M60 Junction 18 Simister Island Interchange

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Peter Freeman
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Re: M60 Junction 18 Simister Island Interchange

Post by Peter Freeman »

Peter Freeman wrote: Fri Jun 26, 2020 03:06 c) Instead of the D4 to D5 transition occurring by lane-gain from the J18 westbound on-ramp, the fifth lane should appear spontaneously before the merge - as far as practicable before. Traffic intending to exit at J17 could thus begin moving leftwards earlier.
Apologies for quoting myself, but to clarify and add:

The above arrangement should mean that most exiting J17 traffic has already occupied the left lane (1 of 5) even before the J18 merge occurs, and it constitutes most of the volume that's in that lane. The merge from J18 would still be tiger-tailed, but not be inordinately long. Vehicles merging in from J18 have a reasonably easy task, not having to contend with many left-moving vehicles, and they can then begin to plan their own move-right.
eg. Melbourne M1 westbound at High Street on-ramp.
https://www.google.com.au/maps/dir/-37. ... m2!4m1!3e0

Another strategy used in AU to ease weaving in short inter-junction lengths is to continue the left lane past the off-ramp diverge, instead of lane-dropping there. The lane drop occurs immediately afterwards, providing a 'last-chance' move-right opportunity. Hopefully this last chance is not required for a large proportion of continuing traffic - just the hesitant or inattentive ones.
eg. Melbourne Eastlink M3 Northbound at Dandenong Bypass.
https://www.google.com.au/maps/@-38.003 ... a=!3m1!1e3

Both of these strategies are employed at several locations with closely-spaced junctions in Melbourne's freeway network, and they are effective.
Last edited by Peter Freeman on Tue Jul 07, 2020 03:57, edited 1 time in total.
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jackal
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Re: M60 Junction 18 Simister Island Interchange

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Peter Freeman wrote: Sun Jun 28, 2020 11:25
jackal wrote: Fri Jun 26, 2020 07:35 There's no space for braiding. The best practical solution to weaving here would be small footprint C/D lanes like M8 J22-J23 or Kingston Bridge (northbound). It might, however, be tricky coming up with a lane allocation appropriate to volumes. D5 lets traffic sort that out for itself.
Unless there's some impediment that's not visible to me when using GSV or GE, then I think the "no space" assessment is pessimistic, or connected with engineering timidity.

The crossover point for the braiding would be west of the stackabout: not on the school grounds, but on the unused land surrounding the power line pylon. The new carriageway would then move close to the M60 mainline before reaching Sandgate Road. The new aperture there could probably be two lanes wide, but possibly one lane only. The new carriageway would run fairly close to housing for a while then, before transforming into the westbound J17 off ramp.
No space as in it would run too close to housing (and the primary school). It is controversial even to turn the HS into a running lane.
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nowster
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Re: M60 Junction 18 Simister Island Interchange

Post by nowster »

Would there be any merit in forcing traffic joining eastbound from J17 to exit via J18 and rejoin the M62, a sort of virtual C/D situation? It's used in other places (eg. A666(M) )
Peter Freeman
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Re: M60 Junction 18 Simister Island Interchange

Post by Peter Freeman »

nowster wrote: Sun Jun 28, 2020 20:51 Would there be any merit in forcing traffic joining eastbound from J17 to exit via J18 and rejoin the M62, a sort of virtual C/D situation? It's used in other places (eg. A666(M) )
That's a good and low-ish cost idea ! - assuming there actually is a weaving problem eastbound between J17 and J18, which seems quite likely. It need not be a "virtual C/D situation". This is what it requires to make it a REAL one -

J17 eastbound on-ramp does not add the fifth lane, but simply runs alongside (north of) the M60 mainline D4ALR as far as the J18 off-ramp diverge. This C/D should be single lane (which will obviously fit, since it would otherwise be lane 1 of 5), and separated from the mainline by a concrete barrier. At the end of the barrier, merging can begin. Having crossed the M66 on the new 3-span bridge, and just before the loop starts to bend leftwards, M62-bound vehicles exit on the right (!) and join the M62 eastbound mainline.

There is STILL a weave, and it might still be hectic, but it occurs off the mainline, probably mostly on the new bridge. Some minor re-design of the J18 off-ramp, the bridge, the loop, and the free-flow-left lane, might be required; and a speed limit should apply.

Will this be an improvement? - I dunno. The better and proper fix is, of course, braiding, similar to westbound.
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nowster
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Re: M60 Junction 18 Simister Island Interchange

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Peter Freeman wrote: Mon Jun 29, 2020 06:49 Will this be an improvement? - I dunno. The better and proper fix is, of course, braiding, similar to westbound.
Obligatory sheesh: https://pathetic.org.uk/unbuilt/m62_relief_road/
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Re: M60 Junction 18 Simister Island Interchange

Post by booshank »

I'd have thought there would be room to shoehorn a cloverstack like that being built at I-57/I-74 if the loops were put in the north and south quadrants ie for M60 clockwise and M66 to M62. I've rotated the image to make the orientation like simister. The M62 to M60 left turn would still be a little substandard because of space constraints.

Image
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Bryn666
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Re: M60 Junction 18 Simister Island Interchange

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booshank wrote: Fri Oct 02, 2020 16:58 I'd have thought there would be room to shoehorn a cloverstack like that being built at I-57/I-74 if the loops were put in the north and south quadrants ie for M60 clockwise and M66 to M62. I've rotated the image to make the orientation like simister. The M62 to M60 left turn would still be a little substandard because of space constraints.

Image
But it doesn't need it. The congestion is M60 to M60 movements. Take them off the roundabout and the whole thing will flow nicely.

The constraints are either side of the junction - the M66 dropping to D2M past Bury and the M60 trying to squeeze 200k AADT through Death Valley.
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booshank
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Re: M60 Junction 18 Simister Island Interchange

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Bryn666 wrote: Fri Oct 02, 2020 17:50
booshank wrote: Fri Oct 02, 2020 16:58 I'd have thought there would be room to shoehorn a cloverstack like that being built at I-57/I-74 if the loops were put in the north and south quadrants ie for M60 clockwise and M66 to M62. I've rotated the image to make the orientation like simister. The M62 to M60 left turn would still be a little substandard because of space constraints.

Image
But it doesn't need it. The congestion is M60 to M60 movements. Take them off the roundabout and the whole thing will flow nicely.

The constraints are either side of the junction - the M66 dropping to D2M past Bury and the M60 trying to squeeze 200k AADT through Death Valley.
Ok it might be a little fantasy like, but I really can't see non-freeflow movements for everything other than M60 traffic providing an acceptable level of service between motorways as busy as this, unless one sets the bar of what is acceptable very low.
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Re: M60 Junction 18 Simister Island Interchange

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I use this junction very regularly. The congestion is M60 to M60. If you want to join the M60 westbound at J18 from the M60 up from J19, don't bother using the left turn slip, you'll get through faster using the roundabout even if you're stopped at the signals because you'll get the lane gain, whereas the freeflow has to merge in, not once but twice.

The entrances onto the roundabout itself other than the two M60 arms rarely block up even at rush hour. Hence why the proposed scheme deals with the actual problems and not a shopping list from road enthusiasts.

The A56/A682 junction causes far more problems (sometimes sending a tailback all the way southwards towards Bury which in turn affects Simister) than the remaining missing freeflow links at Simister itself. I'd rather have a new interchange there.
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booshank
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Re: M60 Junction 18 Simister Island Interchange

Post by booshank »

Bryn666 wrote: Fri Oct 02, 2020 18:28 I use this junction very regularly. The congestion is M60 to M60. If you want to join the M60 westbound at J18 from the M60 up from J19, don't bother using the left turn slip, you'll get through faster using the roundabout even if you're stopped at the signals because you'll get the lane gain, whereas the freeflow has to merge in, not once but twice.

The entrances onto the roundabout itself other than the two M60 arms rarely block up even at rush hour. Hence why the proposed scheme deals with the actual problems and not a shopping list from road enthusiasts.

The A56/A682 junction causes far more problems (sometimes sending a tailback all the way southwards towards Bury which in turn affects Simister) than the remaining missing freeflow links at Simister itself. I'd rather have a new interchange there.
I've never been to Manchester, but it's hard to believe that non-freeflow links can provide an acceptable LOS. I'd suggest the proposed scheme sets the bar of its aims pretty low, as can be seen by the "inner links" option. Maybe the money could be better spend elsewhere, that's fine, but let's not pretend it's going to be a good LOS.

As a comparison the M60-M62 seem to carry 115 - 160 000 vehicles/day and the M66-M60 100 000 vehicles/day. I-57 and I-74 are listed as carrying 33 600 and 38 400 vehicles per day. Now even accounting for differences between Murca and here, it's implausible to think non-freeflow links are going to provide a good LOS on roads carrying three or four times as much traffic.

Simister is considerably busier than Almondsbury which I'd say definitely isn't overkill, though showing its age with only two through lanes and no lane gain on the M4 westbound.
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Re: M60 Junction 18 Simister Island Interchange

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We have a finite roads budget. If you've never used the junction how can you profess to know what it needs?
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Re: M60 Junction 18 Simister Island Interchange

Post by booshank »

Bryn666 wrote: Fri Oct 02, 2020 20:31 We have a finite roads budget. If you've never used the junction how can you profess to know what it needs?
I don't think you need to have used a junction to know that a non-freeflow interchange on a roads carrying ~ 100-160 000 vehicles per day is going to provide a low LOS. As I said, the money may well be better spent elsewhere. That's not the issue, but it doesn't change the fact that the result is substandard.
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Re: M60 Junction 18 Simister Island Interchange

Post by booshank »

Here's a strictly fantasy solution: enclose Simister village in a loop!Image
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Re: M60 Junction 18 Simister Island Interchange

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booshank wrote: Fri Oct 02, 2020 21:06
Bryn666 wrote: Fri Oct 02, 2020 20:31 We have a finite roads budget. If you've never used the junction how can you profess to know what it needs?
I don't think you need to have used a junction to know that a non-freeflow interchange on a roads carrying ~ 100-160 000 vehicles per day is going to provide a low LOS. As I said, the money may well be better spent elsewhere. That's not the issue, but it doesn't change the fact that the result is substandard.
For a kick off UK highway engineering does not use the American LOS definitions so that isn't apples with apples. The questions we ask are:

Is the current junction a safety concern?
Is the current junction negatively impacting the local economy?
How do we spend limited resources in an appropriate way?

Given that the proposal with the loop is to remove the signals entirely from Simister Island because the traffic problem will have been taken away, I think that explains why nothing more is planned here. Comparatively few people are making the turning movements you are insistent on spending millions on fixing.

Now if HE instead press ahead with the absolutely shocking inner bridges option instead they will increase collisions purely due to driver confusion, and in 5 years time after it is completed they'll be back to do a local safety scheme with more signs and paint and Switch Island style LED studs because they wanted to keep all the conflicts that make the junction not work in the first place.
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Re: M60 Junction 18 Simister Island Interchange

Post by booshank »

Bryn666 wrote: Fri Oct 02, 2020 21:15
booshank wrote: Fri Oct 02, 2020 21:06
Bryn666 wrote: Fri Oct 02, 2020 20:31 We have a finite roads budget. If you've never used the junction how can you profess to know what it needs?
I don't think you need to have used a junction to know that a non-freeflow interchange on a roads carrying ~ 100-160 000 vehicles per day is going to provide a low LOS. As I said, the money may well be better spent elsewhere. That's not the issue, but it doesn't change the fact that the result is substandard.
For a kick off UK highway engineering does not use the American LOS definitions so that isn't apples with apples. The questions we ask are:

Is the current junction a safety concern?
Is the current junction negatively impacting the local economy?
How do we spend limited resources in an appropriate way?

Given that the proposal with the loop is to remove the signals entirely from Simister Island because the traffic problem will have been taken away, I think that explains why nothing more is planned here. Comparatively few people are making the turning movements you are insistent on spending millions on fixing.

Now if HE instead press ahead with the absolutely shocking inner bridges option instead they will increase collisions purely due to driver confusion, and in 5 years time after it is completed they'll be back to do a local safety scheme with more signs and paint and Switch Island style LED studs because they wanted to keep all the conflicts that make the junction not work in the first place.
No need to get so defensive! I'm not insisting on anything. There may be no economic case for anything better. That would probably depend on what assumptions are made.

Whether or not level of service is used doesn't mean it doesn't exist in terms of how well traffic flows, how likely it is to be held up, points of conflict etc. That reality is going to exist at an interchange whether it is measured or not.

What are the turning movement numbers? From the numbers on the mainlines, and how they change through the interchange, they seem rather sizable.
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Re: M60 Junction 18 Simister Island Interchange

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The current scheme is very well designed, but will not remove the need for more freeflow in the fullness of time. For one thing, think of the suppressed demand that the upgrade will release (e.g., M60 nb to M62 traffic that currently braves Broadway), for another just look at Lofthouse.

It might be considered whether freeflow for M60 nb to M62 and M66 to M60 wb could be put under the 'big blue' M60/M62 bridge for a cloverstack-type configuration. With a sufficiently high skew the horizontal alignment looks fairly straightforward, so it's a question of whether the bridge is high enough or could be made so. It will need a major refurbishment at some point and could potentially have the deck jacked higher.
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Re: M60 Junction 18 Simister Island Interchange

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jackal wrote: Sat Oct 03, 2020 11:42 The current scheme is very well designed, but will not remove the need for more freeflow in the fullness of time. For one thing, think of the suppressed demand that the upgrade will release (e.g., M60 nb to M62 traffic that currently braves Broadway), for another just look at Lofthouse.

It might be considered whether freeflow for M60 nb to M62 and M66 to M60 wb could be put under the 'big blue' M60/M62 bridge for a cloverstack-type configuration. With a sufficiently high skew the horizontal alignment looks fairly straightforward, so it's a question of whether the bridge is high enough or could be made so. It will need a major refurbishment at some point and could potentially have the deck jacked higher.
I personally think it's more likely the M62 to M66 movement will need a freeflow before the M60 to M62 will and this could be achieved with landtake to the north; likely as old habits die hard and Broadway will continue to be the preferred route for traffic - stick freeflow at M62 J20 for this - the room exists.
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Re: M60 Junction 18 Simister Island Interchange

Post by jackal »

Why not both?
M60 J18 - Copy.png
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Re: M60 Junction 18 Simister Island Interchange

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That's probably the long term aspiration. Quite a tidy fix that and keeping the same vertical levels of the existing interchange so little impact on the village.
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Re: M60 Junction 18 Simister Island Interchange

Post by jackal »

It seems the loop option has been selected :D

https://www.burytimes.co.uk/news/190406 ... r-reality/

I can't find the actual preferred route announcement (maybe out later today) but here's the consultation report which found "397 strongly supporting the Northern Loop option compared to 65 strongly supporting the Inner Links option":

https://highwaysengland.citizenspace.co ... _final.pdf

PS - A staggering consultation response from Manchester City Council: "Overall view of scheme: As the scheme does not directly impact Manchester, a response is not felt to be needed".
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