M6 J10 Improvements

[Peter Freeman]

£78m motorway scheme 'makes no difference'

www.bbc.com/news/articles/cxrwqrqd72do

Well - surprise, surprise!

[Bryn666]

£78m motorway scheme 'makes no difference'

www.bbc.com/news/articles/cxrwqrqd72do

Who didn't see this one coming?

[Big L]

I seem to recall saying, before a shovel had hit the ground, that all this was just going to make the queues shorter but wider, and no quicker.

[Bryn666]

I seem to recall saying, before a shovel had hit the ground, that all this was just going to make the queues shorter but wider, and no quicker.

I'd love to see what garbage went into the traffic model to say it would be more efficient. They should've just been honest and said it was a bridge replacement scheme and reshuffling of the existing roundabout.

[tom1977]

I seem to recall saying, before a shovel had hit the ground, that all this was just going to make the queues shorter but wider, and no quicker.

I'd love to see what garbage went into the traffic model to say it would be more efficient. They should've just been honest and said it was a bridge replacement scheme and reshuffling of the existing roundabout.

Shorter queue lengths + improved merge and diverge capacity + better safety on mainline = overall delay is unchanged for the slip roads + worse for anyone not on the SRN approaches + standard NH approach to network interfaces

[Chris5156]

Doesn't bode well for Wisley, does it?

[Peter Freeman]

Unfortunately, NH will be able to produce statistics that show improvement, ie shorther delays leading to improved journey times. In other words, it has been improved - just a little bit.

That's the first trouble with these ill-advised and poor-BCR tinkerings. The second trouble is that they effectively immunise a location, for many years, against a proper improvement. This one denies us a link from M6Toll to M54 that really performs.

[Truvelo]

This one denies us a link from M6Toll to M54 that really performs.

But even that has the same bodge at M6 J11 which will simply provide more lanes at the roundabout to hold the queues.

[Peter Freeman]

This one denies us a link from M6Toll to M54 that really performs.

But even that has the same bodge at M6 J11 which will simply provide more lanes at the roundabout to hold the queues.

Oops - thanks - I got my J10/J11 mixed up . Yes, it's J11 that's the spoiler for the M6Toll connection.

[fras]

Surely, in theory, for a fixed length of road available for a queue, increasing the number of lanes in that queue increases the number of vehicles that can (1) queue up at a signal, and (2) on green, pass the traffic signal they queue at. So capacity of the junction is, theoretically, increased.
Of course, I realise this is not as simple as it sounds, as this is a massive roundabout, so one set of signal lights leads on to another, so the traffic lights program is key. It was my understanding that a period has to be allowed from initial commissioning so that traffic movements can be assessed, and the lights program adjusted to maximise throughput. Of course one overriding consideration must surely be to prevent traffic leaving the motorway from being held up so the queue tails back onto the motorway.

[Peter Freeman]

You're exactly right about the number of lanes. So this WILL help, slightly. The point is, though, think what could have been done instead, for similar or lower cost. (Several good options).

[jackal]

My complaints are (1) that they should be adding left turn freeflow not removing it, and (2) a big signalised rbt is an inherently limited design. Better alternatives would be a stackabout (which was considered), DDI, or SPUI, with the B road reduced to a merge or LILO with the onslip.

[ReissOmari]

I had to deal with this roundabout a couple days ago, had a near miss as a Range Rover was in the M6 Southbound lane but decided last minute to push over to come into Walsall, the lines on the road need to be adjusted, maybe with the smaller dotted lines to guide each lane around, I can imagine there's been a few near misses there already.

Another thing, for a roundabout of such size with so many lanes, I'm not sure why the secondary signals are so close to the primary, they should all have been further away, for example, if there's congestion and you pass the stop line and the lights change, you're unaware and can't see when they change back to green unless you can reverse! (Not that you should be crossing the stop line, but it happens).

I would have expected a traffic signal set up like the ones on M1 J33, including the mast traffic signals too. Overall, feels like a cheap job, as mentioned a free flowing slip road into Walsall from Northbound and Wolves from Southbound should have been implemented, I feel like M6 J19 set up would have worked here too. On top of that they are, what?, 2 years delayed? Not good.

[jnty]

Would it be reasonable to say that a 4-lane roundabout dealing with 5 or more entry/exit pairs is basically at or beyond the limit of where incremental roundabout improvements can significantly help with congestion? Especially on trunk roads where a significant proportion of drivers are not going to be regular users?

I'm basically looking at this from the same perspective as fras - at a high level, if you have lots of pipes of traffic and join them together with one big pipe at a junction, then it stands to some kind of reason that making the big pipe even bigger should make things proportionally better. Life isn't that simple but - in this situation - why not? Are NH underestimating the diminishing returns you get from larger and larger roundabouts, and if so, why?

[jackal]

I'm basically looking at this from the same perspective as fras - at a high level, if you have lots of pipes of traffic and join them together with one big pipe at a junction, then it stands to some kind of reason that making the big pipe even bigger should make things proportionally better. Life isn't that simple but - in this situation - why not? Are NH underestimating the diminishing returns you get from larger and larger roundabouts, and if so, why?

A roundabout is a very efficient arrangement where the volumes allow it to function as an actual roundabout, as most users will stop only momentarily or not at all, which is better than the frequent stops at signalised junctions.

But in cases like J10 it's no longer functionally a roundabout but rather a series of poorly arranged signalised junctions, with right turns going through three sets of light. It is simply less efficient than designs optimised for signals like the SPUI, DDI or even the humble diamond, which have only one or two sets of signals for right turns. For instance, the roundabout makes opposite right turns (e.g. nb to eb and sb to wb) cross each other twice for no good reason, whereas they don't cross at all in an SPUI.

This is all consistent with it being true that wider approaches and circulatory carriageways improve throughput at a signalised rbt. You can brute force an inefficient design to handle a bit more traffic if you throw enough money at it (like £85m here, or £317m for the three-level version at Wisley). But that doesn't stop it from being inefficient, and you'd get a lot more bang for your buck with a DDI or SPUI. They also benefit from wider carriageways but without suffering from the drag factor of pointlessly conflicting traffic flows.

[Bryn666]

I'm basically looking at this from the same perspective as fras - at a high level, if you have lots of pipes of traffic and join them together with one big pipe at a junction, then it stands to some kind of reason that making the big pipe even bigger should make things proportionally better. Life isn't that simple but - in this situation - why not? Are NH underestimating the diminishing returns you get from larger and larger roundabouts, and if so, why?

A roundabout is a very efficient arrangement where the volumes allow it to function as an actual roundabout, as most users will stop only momentarily or not at all, which is better than the frequent stops at signalised junctions.

But in cases like J10 it's no longer functionally a roundabout but rather a series of poorly arranged signalised junctions, with right turns going through three sets of light. It is simply less efficient than designs optimised for signals like the SPUI, DDI or even the humble diamond, which have only one or two sets of signals for right turns. For instance, the roundabout makes opposite right turns (e.g. nb to eb and sb to wb) cross each other twice for no good reason, whereas they don't cross at all in an SPUI.

This is all consistent with it being true that wider approaches and circulatory carriageways improve throughput at a signalised rbt. You can brute force an inefficient design to handle a bit more traffic if you throw enough money at it (like £85m here, or £317m for the three-level version at Wisley). But that doesn't stop it from being inefficient, and you'd get a lot more bang for your buck with a DDI or SPUI. They also benefit from wider carriageways but without suffering from the drag factor of pointlessly conflicting traffic flows.

The refusal to entertain SPUI and DDIs here is simply a symptom of "we know best" nationalism in highways design. The fact no-one else is copying our interchange design whereas Europe is now trialling DDIs and the like (see Belgium of all places) suggests we are much happier being stubborn island doing the same thing over and over whilst everyone else evolves. It's a disease that leaks through our bureaucracy at all levels.

[KILLER KNIGHT]

It's always been like that - when I commuted from Tamworth to Birmingham they were building the M42 from J9-J10, then when I commuted from Tamworth to Derby they were building the A42 !

LOL that’s so sad! Had they built the original M42 as intended, you wouldn’t have had to go through the trouble of them building the A42!

I suspect that if the A42 had been built to motorway standard north of junction 11, it would still have been phased later than the southern stretches.

Since the M42 is only 2 lane north of junction 9, there's little difference in practice between that section of M42 and the A42.

It was meant to reach Nottingham.

[KILLER KNIGHT]

LOL that’s so sad! Had they built the original M42 as intended, you wouldn’t have had to go through the trouble of them building the A42!

The first section of the M42 was a simple link road from the M6 to Birmingham Airport and the NEC. It opened in the mid 70's when money was really tight after the 1970's depression and it was 1985 before it went any farther. Even so you got the A42 because they ran out of money before reaching the M1 !

Let me remind you of the interest rate in 1986, it was pushing 8% and that was low by the standards of the time.

This is why usury must be banned.

[Ruperts Trooper]

LOL that’s so sad! Had they built the original M42 as intended, you wouldn’t have had to go through the trouble of them building the A42!

The first section of the M42 was a simple link road from the M6 to Birmingham Airport and the NEC. It opened in the mid 70's when money was really tight after the 1970's depression and it was 1985 before it went any farther. Even so you got the A42 because they ran out of money before reaching the M1 !

Let me remind you of the interest rate in 1986, it was pushing 8% and that was low by the standards of the time.

This is why usury must be banned.

It used to be at least capped - back in the '70s the Money Lenders Act limited interest rates to 48% per annum and was used by loan companies for unsecured loans - subsequently that limit has been abolished so now there is no top limit and can rise to over 1000%.

The general public can't seem to get it's head around interest rates - for decades banks charged differential overdraft rates depending on whether it was approved in advance or not, typically 20% for approved and 40% for non-approved, but when the differential was banned a couple of years ago the banks simply doubled the approved rate to be the same as the non-approved - no-one seems to have batted an eyelid!

[Big L]

I’ve just driven through junction 10.

Sit down and brace yourselves…

M6 has 4 lanes open in both directions and no temporary speed limits.

Don’t know about the roundabout, but the M6 seems to finally be done !!!