M25 J23-27

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Re: M25 J23-27

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Hi!

Regarding unforseen breakdowns, apart from defective batteries, tyres, out of fuel or (to a lesser extent) overheating, sudden failure of engine timing gear or vital electronics failure are both catastrophic failures that occur with little or no warning that even a scrupulously–followed servicing routine doesn't entirely prevent – there have been a number of BMW N47 diesels fail catastrophically at speed on the motorway due to the cheaply made components in the earliest engines failing!

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Re: M25 J23-27

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Chris5156 wrote: Wed Oct 09, 2019 20:34
thatapanydude wrote: Wed Oct 09, 2019 20:25Moreover, a longer term ambition should be to extend the motorway to Borehamwood which would bring about full-size lanes and an improvement in safety.
For me, a more worthwhile improvement would be to build the Scratchwood Link and connect Stirling Corner roundabout to M1 J3... but I don't think either of those is going to happen.
Likewise, I agree with this! Hendon and Mill-Hill would see great benefits. I have had the opportunity to walk around the A41 at Hendon recently and its clear that the area's around the station could do with some regeneration, which would be helped by shifting traffic onto the M1.
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Re: M25 J23-27

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A303Chris wrote: Thu Oct 24, 2013 13:17 I read this from the head of the Highways Agency Graham Dalton in this months Highway Magazine on this scheme and the following is a quote.

"We know managed motorways work and they perform well. We also know they're safre and that drivers like them. The bit on the M25 (J5-7 and J23-27) is what we call mananged motorways all lanes running. It will be dual four lane at all times with full running capacity using the variable speed limit to give a measured and controlled flow. So we get extra capacity through a fourth lane, steady through put, lane utilisation and fewer incidents to disrupt flow. This will become the standard method of increasing motorway capacity"

This has left me with some queries.

1) Isnt this the same as the widening J16 to J23 and J27 to J30 which is D4 with intermittent hard shoulders through some structures but a variable speed limit ?

2) Or is it a total removal of Hard Shoulder as is the case through junctions 9 and 10 of M6 which is used as the fourth lane ?

3) if it is 2 while this may be acceptable for short dictances through junctions is it really safe to remove the hard shoulder for 17 miles of the M25 (J23 to J27) and 13 miles (J5 to J7), especially as the rest of the motorway bar J3 to J5 will be D4 with hard shoulder?

To me this approach is worrying and I can see the limit be permanently set at 50 or 60mph.
Hmmm.....

17 miles seems like baby steps compared to now. And it's only been 8 years!

Perhaps this thread should be used to discuss how well the flagship stopped vehicle detection works, given this stretch has actually been graced with it.
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Re: M25 J23-27

Post by thatapanydude »

Some thoughts on this section after driving extensively over a few months:

1) South Mimms entry to the M25 eastbound is always very slow causing the mainline to be blocked off. Would a solution here be an extension of the merge into the 2nd lane, D5 to Potters Bar or free flowing one of the A1 entries into the M25 eastbound (I would suggest A1 North to M25 East).

2) The concreate section (Potters Bar to Enfield) especially when dark or raining makes it hard to read out the lane markings? Could tarmac be put over the top of the concreate? Lighting would probably make a big difference.

3) Its clear the lane marking have been narrowed which makes overtaking lorries a bit hairy. Therefore I find myself in lane 3 or 4 most of the time, which many others do as well not forgetting the risk of a stop vehicle in lane 1. This means at times lane 1 or 2 is rather empty, I am not sure what can be done to change this bar a proper widening job or resizing lanes to full size?

4) With the narrow lanes and other points above etc I find myself maxing out at 70mph which I find okay. I do remember at one to be hitting 80mph after the Waltham Cross tunnel and having to break hard for the camera. If there are no signs for national speed limit - are they switched off?

5) I find Waltham Cross to the M11 the best section, though this has some decent verges, a fair bit of HS and a traditional tarmac surface which does not feel as narrow.
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Re: M25 J23-27

Post by WHBM »

I understand that expanding the concrete surfaced section was more challenging that the asphalt section - certainly looked that way during the works, and thus the lane specs are down to the minimum for normal running.

The dark/raining/both lane marking difficulty on concrete surfacing is real Traffic Engineering 1.01, the sort that HA/HE/NH have always been so readily willing to bin when it suits them. When the road was built it was of course specifically designed so the lane markings coincided with the seam lines of the concrete laying, because this very issue was well known and understood. The ALR alterations not only cast this aside, but move around as the lane width adjustments were done in different ways as you go along. Plus, of course, the road lighting was removed. Look at these examples at the same place :

2008, lane markings coincide with the concrete jointing seams :

https://www.google.com/maps/@51.6876931 ... 312!8i6656

2021, markings no longer coincide and are all over the place. Seam lines as prominent as markings (and more so in adverse conditions) :

https://www.google.com/maps/@51.6876144 ... 384!8i8192
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Re: M25 J23-27

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thatapanydude wrote: Mon Nov 15, 2021 11:053) Its clear the lane marking have been narrowed which makes overtaking lorries a bit hairy. Therefore I find myself in lane 3 or 4 most of the time, which many others do as well not forgetting the risk of a stop vehicle in lane 1. This means at times lane 1 or 2 is rather empty, I am not sure what can be done to change this bar a proper widening job or resizing lanes to full size?
You could move left? :wink:

There's not much that can be done about this; it happens on most four-lane motorways regardless of whether they're Smart Motorways or not. The other day, for example, I was alone in lane 1 on the M40 between Denham and High Wycombe, with an empty lane 2 next to me and lanes 3 and 4 full of cars. All four lanes there are full width. As a result, I'm not sure that narrow lanes have a lot to do with it; for what it's worth lanes 3 and 4 are the narrow ones on a Smart Motorway while lanes 1 and 2 are full width or very close to it. It's always just struck me as poor lane discipline and lazy driving. Don't be one of them is my advice!
With the narrow lanes and other points above etc I find myself maxing out at 70mph which I find okay. I do remember at one to be hitting 80mph after the Waltham Cross tunnel and having to break hard for the camera. If there are no signs for national speed limit - are they switched off?
No, the cameras are always live, the speed at which they trigger just varies depending on the speed limit.
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Re: M25 J23-27

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Chris5156 wrote: Mon Nov 15, 2021 12:23
thatapanydude wrote: Mon Nov 15, 2021 11:053) Its clear the lane marking have been narrowed which makes overtaking lorries a bit hairy. Therefore I find myself in lane 3 or 4 most of the time, which many others do as well not forgetting the risk of a stop vehicle in lane 1. This means at times lane 1 or 2 is rather empty, I am not sure what can be done to change this bar a proper widening job or resizing lanes to full size?
You could move left? :wink:

There's not much that can be done about this; it happens on most four-lane motorways regardless of whether they're Smart Motorways or not. The other day, for example, I was alone in lane 1 on the M40 between Denham and High Wycombe, with an empty lane 2 next to me and lanes 3 and 4 full of cars. All four lanes there are full width. As a result, I'm not sure that narrow lanes have a lot to do with it; for what it's worth lanes 3 and 4 are the narrow ones on a Smart Motorway while lanes 1 and 2 are full width or very close to it. It's always just struck me as poor lane discipline and lazy driving. Don't be one of them is my advice!
With the narrow lanes and other points above etc I find myself maxing out at 70mph which I find okay. I do remember at one to be hitting 80mph after the Waltham Cross tunnel and having to break hard for the camera. If there are no signs for national speed limit - are they switched off?
No, the cameras are always live, the speed at which they trigger just varies depending on the speed limit.
Yes, it's entirely down to lazy driving and "I know best" because they still believe there's such thing as a "poverty car lane" and a "rich successful Audi lane".
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Re: M25 J23-27

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thatapanydude wrote: Mon Nov 15, 2021 11:05
2) The concreate section (Potters Bar to Enfield) especially when dark or raining makes it hard to read out the lane markings? Could tarmac be put over the top of the concreate? Lighting would probably make a big difference.
Tarmac on top of concrete is a bit nasty.. it expands at a different rate, and has a tendancy to crack and break off the surface all over the place. It wouldn't also give a good ride, as the concrete itslef doesn't have the same substrata that a road of tarmac construction uses. When converting the M11 from 7-9, HA at the time took the approach of taking it all up and starting again; I'm sure that's what also will happen to the M25 there at some point.

Lighting, unfortunately, won't be making a come back any time soon.
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Re: M25 J23-27

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c2R wrote: Mon Nov 15, 2021 13:03
thatapanydude wrote: Mon Nov 15, 2021 11:05
2) The concreate section (Potters Bar to Enfield) especially when dark or raining makes it hard to read out the lane markings? Could tarmac be put over the top of the concreate? Lighting would probably make a big difference.
Tarmac on top of concrete is a bit nasty.. it expands at a different rate, and has a tendancy to crack and break off the surface all over the place. It wouldn't also give a good ride, as the concrete itslef doesn't have the same substrata that a road of tarmac construction uses. When converting the M11 from 7-9, HA at the time took the approach of taking it all up and starting again; I'm sure that's what also will happen to the M25 there at some point.

Lighting, unfortunately, won't be making a come back any time soon.
The Surrey section, and many US concrete freeways, uses black outlines around road markings. In fact this practice is so old the M1 had it between J5-10 in 1959: https://i2-prod.coventrytelegraph.net/i ... 463542.jpg
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Re: M25 J23-27

Post by Peter Freeman »

Bryn666 wrote: Mon Nov 15, 2021 14:26 The Surrey section, and many US concrete freeways, uses black outlines around road markings. In fact this practice is so old the M1 had it between J5-10 in 1959: https://i2-prod.coventrytelegraph.net/i ... 463542.jpg
This is the practice on some Australian concrete roads too.
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Re: M25 J23-27

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Chris5156 wrote: Mon Nov 15, 2021 12:23
thatapanydude wrote: Mon Nov 15, 2021 11:053) Its clear the lane marking have been narrowed which makes overtaking lorries a bit hairy. Therefore I find myself in lane 3 or 4 most of the time, which many others do as well not forgetting the risk of a stop vehicle in lane 1. This means at times lane 1 or 2 is rather empty, I am not sure what can be done to change this bar a proper widening job or resizing lanes to full size?
You could move left? :wink:
To be honest I do my best when on a traditional D4(M) with HS to stay on the left unless overtaking. However, on the most regular stretch of D4(M) I use which is the A1(M) from Alconbury to Peterborough, most often lane 1 is full of lorries and if I want to cruise along at 80mph (which is on this stretch not fast at all) generally mixing between lane 2 and 3 is optimal. I am against just cruising in a lane of your choice doing 65mph odd but I think its okay staying on the right hand lanes if you are making progress.

However on a smart motorway, I don't use the inner lanes 1 and 2 because:

1) Lane 1 has the risk of a stopped vehicles, and if there is one cars will flood into the lane 2 at quite short notice.
2) Narrow lanes make overtaking a lorry a bit to tight for my liking esp. when they are as many times I have seen concentrating on the phone or a European Lorry who by virtue of being left hand driven can't see me as well.

c2R wrote: Mon Nov 15, 2021 13:03 I'm sure that's what also will happen to the M25 there at some point.
Really ought to have been done while doing the SM works - a real missed opportunity.
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Re: M25 J23-27

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thatapanydude wrote: Thu Nov 18, 2021 22:09
However on a smart motorway, I don't use the inner lanes 1 and 2 because:

1) Lane 1 has the risk of a stopped vehicles, and if there is one cars will flood into the lane 2 at quite short notice.
I've heard of "Lane 1 refusal" on smart motorways (due to the stopped vehicle risk) a few times and I'm curious about the safety calculus at play.

How do you drive on very busy non-hard-shoulder D2 roads? Are there any very busy S1s you'd completely avoid on the same basis?
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Re: M25 J23-27

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jnty wrote: Wed Nov 24, 2021 18:55
thatapanydude wrote: Thu Nov 18, 2021 22:09
However on a smart motorway, I don't use the inner lanes 1 and 2 because:

1) Lane 1 has the risk of a stopped vehicles, and if there is one cars will flood into the lane 2 at quite short notice.
I've heard of "Lane 1 refusal" on smart motorways (due to the stopped vehicle risk) a few times and I'm curious about the safety calculus at play.

How do you drive on very busy non-hard-shoulder D2 roads? Are there any very busy S1s you'd completely avoid on the same basis?
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Re: M25 J23-27

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jnty wrote: Wed Nov 24, 2021 18:55
thatapanydude wrote: Thu Nov 18, 2021 22:09
However on a smart motorway, I don't use the inner lanes 1 and 2 because:

1) Lane 1 has the risk of a stopped vehicles, and if there is one cars will flood into the lane 2 at quite short notice.
I've heard of "Lane 1 refusal" on smart motorways (due to the stopped vehicle risk) a few times and I'm curious about the safety calculus at play.

How do you drive on very busy non-hard-shoulder D2 roads? Are there any very busy S1s you'd completely avoid on the same basis?
D2s are seldom as busy as smart motorways, so the incidence of stopped vehicles is much rarer. Also there is usually some way that vehicles can pull mostly off the carriageway, as armco barrier is not generally installed right up to the edge of the running lane.

What very busy S1s did you have in mind? This sounds like a contradiction in terms.
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Re: M25 J23-27

Post by ManomayLR »

Chris Bertram wrote: Thu Nov 25, 2021 11:47 What very busy S1s did you have in mind?
Well there's the A303 but I guess that's slow-moving.
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Re: M25 J23-27

Post by jackal »

In practice I'm sure lane 1 refusers in a D4 ALR are essentially the same as the refusers in a D3M. You go from a D3M operating somewhat like a D2M to a D4 operating somewhat like a D3, so you're still gaining a lane even if you end up with only 3 lanes fully utilised.

All the ALR post-opening reports show increased volumes and decreased congestion as one would expect from an extra lane.
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Re: M25 J23-27

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EpicChef wrote: Thu Nov 25, 2021 12:22
Chris Bertram wrote: Thu Nov 25, 2021 11:47 What very busy S1s did you have in mind?
Well there's the A303 but I guess that's slow-moving.
...and S2.... Probably the busiest S1 I've seen is something like the old A830 out of Mallaig before it was upgraded.
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Re: M25 J23-27

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Chris Bertram wrote: Thu Nov 25, 2021 11:47
jnty wrote: Wed Nov 24, 2021 18:55
thatapanydude wrote: Thu Nov 18, 2021 22:09
However on a smart motorway, I don't use the inner lanes 1 and 2 because:

1) Lane 1 has the risk of a stopped vehicles, and if there is one cars will flood into the lane 2 at quite short notice.
I've heard of "Lane 1 refusal" on smart motorways (due to the stopped vehicle risk) a few times and I'm curious about the safety calculus at play.

How do you drive on very busy non-hard-shoulder D2 roads? Are there any very busy S1s you'd completely avoid on the same basis?
D2s are seldom as busy as smart motorways, so the incidence of stopped vehicles is much rarer. Also there is usually some way that vehicles can pull mostly off the carriageway, as armco barrier is not generally installed right up to the edge of the running lane.

What very busy S1s did you have in mind? This sounds like a contradiction in terms.
Presumably the stopped vehicle risk isn't so much a function of absolute traffic as it is in terms of traffic per lane? The Oxford section of the A34 or the A720 aren't as strictly as busy as some motorways but certainly feel much busier as it's all crammed into two lanes. And yes, whoops, I meant S2. Stranded vehicles are a different problem entirely on S1s!
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Re: M25 J23-27

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jnty wrote: Thu Nov 25, 2021 12:38
Chris Bertram wrote: Thu Nov 25, 2021 11:47
jnty wrote: Wed Nov 24, 2021 18:55
I've heard of "Lane 1 refusal" on smart motorways (due to the stopped vehicle risk) a few times and I'm curious about the safety calculus at play.

How do you drive on very busy non-hard-shoulder D2 roads? Are there any very busy S1s you'd completely avoid on the same basis?
D2s are seldom as busy as smart motorways, so the incidence of stopped vehicles is much rarer. Also there is usually some way that vehicles can pull mostly off the carriageway, as armco barrier is not generally installed right up to the edge of the running lane.

What very busy S1s did you have in mind? This sounds like a contradiction in terms.
Presumably the stopped vehicle risk isn't so much a function of absolute traffic as it is in terms of traffic per lane? The Oxford section of the A34 or the A720 aren't as strictly as busy as some motorways but certainly feel much busier as it's all crammed into two lanes. And yes, whoops, I meant S2. Stranded vehicles are a different problem entirely on S1s!
The only two times I have been rear-ended in traffic were here on the A56: https://goo.gl/maps/JfAAeSXkjhAPQwwh6 when it was down to narrow lanes for lighting replacement works in 2010. People doing the "there's never any stopped traffic in Lane 2" mindset and wham. Thankfully both very low speed impacts with nothing beyond minor car damage in both cases, but infuriating all the same.

1970s D2s are often far more stressful to drive on than D3M or even ALR.
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Re: M25 J23-27

Post by jnty »

Bryn666 wrote: Thu Nov 25, 2021 13:37 1970s D2s are often far more stressful to drive on than D3M or even ALR.
Definitely - having been used to the A720 which tends to slow down quite sharply as the weight of traffic increases (and does have some hard shoulder sections), the A34 surprised me in how busy it can be while still maintaining 70+ mph (and very close spacing between vehicles.) I guess it must be to do with gradients and frequency of junctions? If I'm on it, I'll be heading from/to some ALR smart motorways sections on the same day, and I know where I feel safer!
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