A1(M) Junction 6 to Junction 8 Smart Motorway

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thatapanydude
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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by thatapanydude » Tue Dec 08, 2020 15:00

c2R wrote:
Tue Dec 08, 2020 13:48
jackal wrote:
Tue Dec 08, 2020 12:01
To be fair the southbound A1 does lose a third of its traffic to the A14 at Brampton so it's somewhat logical that that's where the quality drops off.

I personally think J6-8 is a higher priority as it's far busier and a glaring D2 bottleneck between D3 sections. Baldock to Brampton is a vastly more expensive long term aspiration that shouldn't be an excuse to hold up more deliverable schemes.
I disagree with that assessment - firstly J6-8 is only really busy when it fills up with commuter traffic centred around Welwyn, Hatfield, Letchworth, Baldock, and Stevenage - for the most the day, there is not a significant issue - this can be seen by the fact that the D2M section south of Hatfield copes fine. I would argue that increasing capacity on this section will only release currently suppressed demand. Have we also got an answer yet as to the level of structure and hard shoulder reconstruction that is required for 6-8? It's a fairly old section of motorway, and so I don't think that it's going to be as straightforward as putting in a couple of ERAs, a concrete barrier, and getting out the white paint...

The section between Brampton and the Black Cat on the otherhand has a number of at grade junctions, poor alignments, and contributes to significant local severence in the villages mentioned above. While it is less busy clearly than the D4M section between Alconbury and Peterborough, there is still a large amount of strategic traffic heading to/from distribution centres at Milton Keynes, and also using the A1/A421/M1 to route towards London. I would therefore argue that Brampton to the Black Cat is more urgent.
Apologises on digressing a bit but I would add that "Brampton to Black Cat" would not be that expensive too. As the Wyboston section is being tided up as part of the A421/8 Black Cat scheme so it only needs straightening up at Southoe and a Buckden bypass - though I my opinion the A14 scheme was a missed opportunity for that with the new tie-in on the A1 leaving a very tight turn to bypass Buckden on the west. Still any scheme ought to be competitive with any smart motorway scheme further south - I agree too that it will almost certainly push traffic issues northwards to the inadequate A505 junction and southwards onto the already overcapacity A414 not-forgetting exacerbating the rush-hour queues at South Mimms and Borehamwood.

My wish would have been at least extending the D3(M) to the end of a new Buckden bypass as part of the A1(M) though any scheme now will we almost certainly all-purpose.
A1/A1(M) >>> M1

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jackal
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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by jackal » Tue Dec 08, 2020 17:21

c2R wrote:
Tue Dec 08, 2020 13:48
The section between Brampton and the Black Cat on the otherhand has a number of at grade junctions, poor alignments, and contributes to significant local severence in the villages mentioned above.
Obviously I agree it would be great to get it upgraded. The question is where do you find ~£1bn from the RIS budget to do that? Cutting J6-8 isn't anything like enough - you'd need to cut 5-10 schemes of that size. There's the rub.
While it is less busy clearly than the D4M section between Alconbury and Peterborough
As an aside I might mention that, unlike Brampton to Black Cat, A1(M) J6-8 is not less busy than north of Alconbury - it carries the same traffic on half the lanes. Hence why ALR is such a no brainer.

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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by c2R » Tue Dec 08, 2020 17:26

jackal wrote:
Tue Dec 08, 2020 17:21
c2R wrote:
Tue Dec 08, 2020 13:48
The section between Brampton and the Black Cat on the otherhand has a number of at grade junctions, poor alignments, and contributes to significant local severence in the villages mentioned above.
Obviously I agree it would be great to get it upgraded. The question is where do you find ~£1bn from the RIS budget to do that? Cutting J6-8 isn't anything like enough - you'd need to cut 5-10 schemes of that size. Which ones?
While it is less busy clearly than the D4M section between Alconbury and Peterborough
As an aside I might mention that, unlike Brampton to Black Cat, A1(M) J6-8 is not less busy than north of Alconbury - it carries the same traffic on half the lanes. Hence why ALR is such a no brainer.
Yes, I'm aware of that - however, the majority of that is during the rush hour gridlock caused by the commuter traffic I mention above... I used to live in a village directly affected by people finding alternative routes around that - which is why I'm also pretty sure that the amount of suppressed demand is so large that providing an additional lane of capacity will just fill up immediately. If we're trying to predict and provide for commuter traffic here, we'd be looking at least at D4M, with potentially collector distributor lanes between some of the junctions...
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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by jackal » Tue Dec 08, 2020 18:09

Relieving villages of rat runners and putting them on motorways instead doesn't sound so bad to me...

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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by trickstat » Tue Dec 08, 2020 19:01

jackal wrote:
Tue Dec 08, 2020 18:09
Relieving villages of rat runners and putting them on motorways instead doesn't sound so bad to me...
For a short period after I started driving (in 1987) I used to commute between Stevenage and Hendon and, coming home, I would sometimes turn off at J6 and go through Knebworth.

Since moving to Letchworth, on the rare occasions when I've been heading northbound during the evening peak, I have occasionally turned off at J6 and headed home via the B656 and various country roads.

Usually (i.e. not this year), there are a couple of times a year when I need to be in SE Stevenage at about 8:30 AM. I will always leave enough time to take the B197 and a circuitous route around the north and east of the town rather than risk the lottery of the A1(M).

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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by Bryn666 » Tue Dec 08, 2020 19:13

jackal wrote:
Tue Dec 08, 2020 18:09
Relieving villages of rat runners and putting them on motorways instead doesn't sound so bad to me...
Only it doesn't. The M65 reduced traffic on the B-road outside my parents old house for a few years but now it's busier than it was before the motorway was built because some genius decided all that new motorway capacity had to be filled by building industrial estates and box sheds along it, thus completely obliterating the function of the M65 as a bypass. J4-5 is the busiest section and it's because everyone is transiting between two massive distribution parks.

Designed for 38,000 AADT by 2010, it carried 51,000.

This has been explained numerous times before that you have to provide measures to prevent induced demand from new roads but planners keep looking at spreadsheets and whinging that mitigation is too expensive so these villages are actually sacrificed at the altar of BCR and swallowed up by shed development spurred on by that massive new road that apparently has to 'service the economy' instead of 'service quality of life' because WebTAG has no method of calculating quality of life but it can quantify all the other crap that unmitigated road building generates as a 'win'.
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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by thatapanydude » Fri Jan 22, 2021 17:27

Just been looking at the AADF here and while 7-8 is at 75k, 6-7 is well up on 2018 and 2017 at 95k!

This along with the A406 2-lane sections nr Walthamstow must be the highest D2 roads.
A1/A1(M) >>> M1

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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by Micro The Maniac » Fri Jan 22, 2021 18:03

Bryn666 wrote:
Tue Dec 08, 2020 19:13
This has been explained numerous times before that you have to provide measures to prevent induced demand from new roads
By induced demand, I assume you include the previously suppressed demand? ie the traffic that would have used the official route but don't because it is too congested?

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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by jackal » Fri Jan 22, 2021 18:11

thatapanydude wrote:
Fri Jan 22, 2021 17:27
Just been looking at the AADF here and while 7-8 is at 75k, 6-7 is well up on 2018 and 2017 at 95k!

This along with the A406 2-lane sections nr Walthamstow must be the highest D2 roads.
A406 through the M11 junction is the highest D2 I've seen (103,997 a few years back). Some discussion: viewtopic.php?f=1&t=41782

That J6-7 number is really extreme though. Some D3Ms have been converted to D4 around that level. Bizarre that even the D3 ALR has dropped out of the programme.

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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by Chris Bertram » Fri Jan 22, 2021 18:32

Micro The Maniac wrote:
Fri Jan 22, 2021 18:03
Bryn666 wrote:
Tue Dec 08, 2020 19:13
This has been explained numerous times before that you have to provide measures to prevent induced demand from new roads
By induced demand, I assume you include the previously suppressed demand? ie the traffic that would have used the official route but don't because it is too congested?
Suppression of demand seems to be the name of the game in some traffic planning circles.
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Re: A1(M) Junction 6 to Junction 8 Smart Motorway

Post by marconaf » Fri Jan 22, 2021 18:46

Chris Bertram wrote:
Fri Jan 22, 2021 18:32
Micro The Maniac wrote:
Fri Jan 22, 2021 18:03
Bryn666 wrote:
Tue Dec 08, 2020 19:13
This has been explained numerous times before that you have to provide measures to prevent induced demand from new roads
By induced demand, I assume you include the previously suppressed demand? ie the traffic that would have used the official route but don't because it is too congested?
Suppression of demand seems to be the name of the game in some traffic planning circles.
The railway only works at all because fares do exactly that. In BR days it was the standard management procedure. It feels like we are seeing a reversal over the decades for different modes (witness HS2) although personally I prefer “predict and provide” to be applied uniformly and then rely on the inherant advantages/disadvantages of different modes to drive usage - rather than have people decide other peoples desires are less worthy than their own and seek to suppress them, or complain when something is built and finally people can advance/ease their life and label it “induced” as if they are just using it out of spite or something.

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