M3 junctions 9 to 14: smart motorway

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jackal
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M3 junctions 9 to 14: smart motorway

Post by jackal »

This scheme is to start construction next year. Details:
The M3 will be converted into a smart motorway between junction 9 (Winchester) and 14 (Southampton). This stretch of road is 13km or 8 miles long. There are slight variations of smart motorway that can be used depending on the layout and configuration of the road.

Between junction 9 (Winchester) to 13 (Eastleigh), the M3 will operate four-lanes in each direction. This is known as ‘all-lane running’ and involves the existing hard shoulder being converted into an additional lane for vehicles.

Road users driving northbound and joining the M3 at junction 14 where the roads converge from the M27 eastbound, westbound and from Southampton will see the M3 operate four lanes and a hard shoulder up to junction 13.

For road users driving southbound from junction 13 (Eastleigh) towards junction 14 (Southampton), the road will transition from four lanes with no hard should shoulder and then split into two separate roads to link to the M27 East and West.

The section of the M3 linking to the M27 eastbound will feature two lanes and a hard shoulder. The section of the M3 linking to the M27 westbound will comprise three lanes with no hard shoulder. The road layout into Southampton will remain as it is now.

The section from after junction 13 (Eastleigh) to junction 14 (Southampton) is a variation of smart motorway known as a ‘controlled motorway’.

Road users will see enhanced signage, information and the deployment of variable speed limits from overhead gantries from junction 9 to junction 14.
So J9-J13 will be in a consistent D4 ALR configuration. J14-J13 northbound stays as D4H while J13-14 southbound gains a lane on the outercarriageway only, giving five lanes total southbound.

HE say that "In 2036, this section of the M3 (junction 9 to 14) is forecast to carry an average of between 63,000 and 86,000 vehicles per day, which is an increase of 20,000 vehicles compared 2015". By UK standards these seem like low volumes at which to be adding the fourth lane. However, they will want to add the electronics and it may make economic sense to add the lane at the same time. At £139m it's a relatively inexpensive upgrade.

https://highwaysengland.co.uk/projects/ ... -motorway/

(Could have sworn there was a thread about this already but couldn't find it.)
Last edited by jackal on Mon Sep 02, 2019 13:10, edited 1 time in total.
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Johnathan404
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Re: M3 junctions 9 to 14: smart motorway

Post by Johnathan404 »

jackal wrote: Mon Sep 02, 2019 12:33 J14-J13 northbound stays as D4H while J13-14 southbound gains a lane on the mainline (innercarriageway) only, giving five lanes total southbound. From the description above it seems the third lane may continue to the M27, though as this would pose merge issues perhaps it actually drops to the A27.
It's the outer carriageway being widened - the one heading towards Bournemouth - unless you're talking in driving terms. I'm not sure that would cause many merging issues as it would only be 5 lanes into 4, but more importantly I can't see them widening all the way to the M27 unless it needs to be done. If the lane were to drop at the A27, I'd like to see the other A27 exit closed - why have a lane drop if people aren't going to use it?
jackal wrote: Mon Sep 02, 2019 12:33By UK standards these seem like low volumes at which to be adding the fourth lane.
Don't forget that the poor alignment of the road, especially the three big hills, considerably lowers the capacity of any lane configuration. Consistent widening is much better than arbitrary climbing lanes.
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jervi
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Re: M3 junctions 9 to 14: smart motorway

Post by jervi »

The thread you were probably think of was on the M3 J9 upgrade thread.
Speaking of which, I wonder if they will do all the landworks and gantries for the smart motorway when they are upgrading the junction?
and then wait for the rest of the scheme to be done before using them.
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Re: M3 junctions 9 to 14: smart motorway

Post by jackal »

^ The smart motorway scheme and J9 improvement will be under construction at the same time (2020-22) and should be well coordinated. And yes, the J9 thread was the closest I could find!
Johnathan404 wrote: Mon Sep 02, 2019 12:38
jackal wrote: Mon Sep 02, 2019 12:33 J14-J13 northbound stays as D4H while J13-14 southbound gains a lane on the mainline (innercarriageway) only, giving five lanes total southbound. From the description above it seems the third lane may continue to the M27, though as this would pose merge issues perhaps it actually drops to the A27.
It's the outer carriageway being widened - the one heading towards Bournemouth
Thanks, will edit OP.
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Re: M3 junctions 9 to 14: smart motorway

Post by Patrick Harper »

So M3S-M27W is going to be D3ALR. I wonder if this is a pretence for D5ALR for M27 J3-J4 (and perhaps D4ALR for J2-J3), given that the new Romsey Road overbridge is being rebuilt for D4M.
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Re: M3 junctions 9 to 14: smart motorway

Post by A303Chris »

To me what is more important is turning the two lane section between J8 and J9 to 3ALR as this is a slog and often crawling at 30 to 50 mph. In fact on returns from the south coast on a Saturday, Sunday of Bank Holiday afternoon I find it quicker to go off the A31 at J1 of the M27, use the A3090, to Winchester, go through the city on the B3040 and B3047 and then come up the A33 to J7. That time of day you fly through Winchester and can sit at a steady 60 mph / 70mph on the A33 (depending if SC or DC) and pass by the queuing traffic on the adjacent M3.

So the 60 mile M3 will be:

J1 to J2 - 3 lanes with HS
J2 to J4A - 4 lanes ALR
J4A to J8 - 3 lanes with HS
J8 to J9 - 2 lanes With HS
J9 to J13 - 4 lanes ALR

That IMO is a lot of changes in the characteristics of the motorway over a relatively short length
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Patrick Harper
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Re: M3 junctions 9 to 14: smart motorway

Post by Patrick Harper »

I've never found J8-J9 an issue during the regular peak hours though, the queue always starts where the A34 joins. The eastern most parts of the A303 have the same sort of traffic situation but they have no HS so there's no cheap upgrade for them.
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Re: M3 junctions 9 to 14: smart motorway

Post by Johnathan404 »

A303Chris wrote: Mon Sep 02, 2019 13:36 To me what is more important is turning the two lane section between J8 and J9 to 3ALR as this is a slog and often crawling at 30 to 50 mph.
"Slog" is indeed the right word to describe J8-9: very rarely stationary (unless it's the tailbacks from J11), but often stuck at the speed of the overtaking vehicles. That is very different to how I would describe J9-14, which would be something like "chronically congested": I can't think of an occasion in the last few years where I have used it and not had to come to a halt.

I'm not surprised the latter is a much higher priority. I count seven alternative routes through the villages that people regularly take to avoid the road. At least with J7-9 the rat-run is relatively harmless (I also don't think it's actually any quicker, but it is a lot more fun).
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Re: M3 junctions 9 to 14: smart motorway

Post by mikehindsonevans »

jackal wrote: Mon Sep 02, 2019 13:09 ^ The smart motorway scheme and J9 improvement will be under construction at the same time (2020-22) and should be well coordinated. And yes, the J9 thread was the closest I could find!
Johnathan404 wrote: Mon Sep 02, 2019 12:38
jackal wrote: Mon Sep 02, 2019 12:33 J14-J13 northbound stays as D4H while J13-14 southbound gains a lane on the mainline (innercarriageway) only, giving five lanes total southbound. From the description above it seems the third lane may continue to the M27, though as this would pose merge issues perhaps it actually drops to the A27.
It's the outer carriageway being widened - the one heading towards Bournemouth
Thanks, will edit OP.
Erm, if I read this correctly, following decades of heading south down the M3 towards the coast....

If you head south along the outer two lanes of the M3S/B towards Southampton, you will find yourself passing the Airport on your way Eastbound towards Portsmouth. Not towards Bournemouth - for that westbound (Bournemouth) slip, you need to be in the lefthand lane. It was the prototype for the M40NB-M42NB junction!
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Re: M3 junctions 9 to 14: smart motorway

Post by RichardA35 »

mikehindsonevans wrote: Tue Sep 03, 2019 15:26
jackal wrote: Mon Sep 02, 2019 13:09 ^ The smart motorway scheme and J9 improvement will be under construction at the same time (2020-22) and should be well coordinated. And yes, the J9 thread was the closest I could find!
Johnathan404 wrote: Mon Sep 02, 2019 12:38
It's the outer carriageway being widened - the one heading towards Bournemouth
Thanks, will edit OP.
Erm, if I read this correctly, following decades of heading south down the M3 towards the coast....

If you head south along the outer two lanes of the M3S/B towards Southampton, you will find yourself passing the Airport on your way Eastbound towards Portsmouth. Not towards Bournemouth - for that westbound (Bournemouth) slip, you need to be in the lefthand lane. It was the prototype for the M40NB-M42NB junction!
Depends how you define the two "outer" lanes - as the ones furthest from the centre or something else...
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Re: M3 junctions 9 to 14: smart motorway

Post by Johnathan404 »

mikehindsonevans wrote: Tue Sep 03, 2019 15:26 Erm, if I read this correctly, following decades of heading south down the M3 towards the coast....

If you head south along the outer two lanes of the M3S/B towards Southampton, you will find yourself passing the Airport on your way Eastbound towards Portsmouth. Not towards Bournemouth - for that westbound (Bournemouth) slip, you need to be in the lefthand lane. It was the prototype for the M40NB-M42NB junction!
You read incorrectly. The full version of the post you quoted states that I am not talking in driving terms, in which case the 'outside' would indeed have referred to the left. This was in response to a post using the phrase "inner carriageway".
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Re: M3 junctions 9 to 14: smart motorway

Post by Micro The Maniac »

It seems perverse to me that they are going to upgrade south of J9 to four lanes, while between J8 and J9 remains as two lanes only - but is a real bottleneck :(
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Re: M3 junctions 9 to 14: smart motorway

Post by Phil »

Micro The Maniac wrote: Tue Sep 03, 2019 16:54 It seems perverse to me that they are going to upgrade south of J9 to four lanes, while between J8 and J9 remains as two lanes only - but is a real bottleneck :(
Not really. LOTS of traffic from the south coast leaves / joins the A34, while similarly lots of traffic joins / leaves at the A303 split.

In any other civilised country that would be recognised by the A34 being a proper motorway not a collection of variable standard A road upgrades.

It strikes me that the only problem you might get on the D2 section is the odd bit of 'elephant racing' between HGVs - consider yourself fortunate - those using the A34 in particular will be facing that for a lot longer than the 10 odd miles you may experience on the M3!
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Re: M3 junctions 9 to 14: smart motorway

Post by Patrick Harper »

If the M3 to the north is made D4ALR from J8 all the way to J6, the south-facing J7 slips and J8 slips will have to be rebuilt akin to M25 J21 so that the A303 motorway spur will lose access to and from J8 (after all, the A30 already has an adequate junction with the A303 at Popham).
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Re: M3 junctions 9 to 14: smart motorway

Post by jackal »

From SABRE maps it seems volumes on J9-14 are consistently over 100k AADT and as high as 140k at J13-14, which makes a lot more sense. I guess the AADTs given by HE are one-directional.

In traffic terms they should add a fifth lane northbound at J14-13. They are presumably not doing this as there is still uncertainty about D5 ALR. M25 J15-16 is supposed to be the testbed but has slipped back to RIS2.
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Re: M3 junctions 9 to 14: smart motorway

Post by Johnathan404 »

jackal wrote: Wed Sep 04, 2019 13:39 In traffic terms they should add a fifth lane northbound at J14-13. They are presumably not doing this as there is still uncertainty about D5 ALR. M25 J15-16 is supposed to be the testbed but has slipped back to RIS2.
I appreciate you've got the figures but in practical terms I'm not sure why that would be needed. The congestion there is frequent but is always caused by traffic trying to pile into three lanes to get through J13, plus HGVs slowing down to climb the hill immediately beyond J13.

Ideally the exit at J13 northbound would be closed, or at least made accessible to traffic coming from the M27 eastbound only. The weaving there is only going to get worse. The north-facing onslip ought to be a lot longer too, as there isn't much room to build up speed.
Skye wrote: Wed Sep 04, 2019 12:13 If the M3 to the north is made D4ALR from J8 all the way to J6, the south-facing J7 slips and J8 slips will have to be rebuilt akin to M25 J21 so that the A303 motorway spur will lose access to and from J8 (after all, the A30 already has an adequate junction with the A303 at Popham).
You're deep in to fantasy territory there. There is no plan to widen J6-8, nor is there any need to do it. Congestion there is (was?) caused by Black Dam Roundabout.
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Re: M3 junctions 9 to 14: smart motorway

Post by jackal »

Johnathan404 wrote: Wed Sep 04, 2019 13:52
jackal wrote: Wed Sep 04, 2019 13:39 In traffic terms they should add a fifth lane northbound at J14-13. They are presumably not doing this as there is still uncertainty about D5 ALR. M25 J15-16 is supposed to be the testbed but has slipped back to RIS2.
I appreciate you've got the figures but in practical terms I'm not sure why that would be needed. The congestion there is frequent but is always caused by traffic trying to pile into three lanes to get through J13, plus HGVs slowing down to climb the hill immediately beyond J13.

Ideally the exit at J13 northbound would be closed, or at least made accessible to traffic coming from the M27 eastbound only. The weaving there is only going to get worse. The north-facing onslip ought to be a lot longer too, as there isn't much room to build up speed.
So you're saying the cause of congestion is the three lane bottleneck and hill, not the weaving? But if the weaving doesn't cause congestion why would you even consider closing J13 nb? I don't really follow.

A common solution to weaving is provision of an additional lane (that's one thing DMRB is not wrong about) so combined with sheer volumes it seems a no brainer.
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Re: M3 junctions 9 to 14: smart motorway

Post by Johnathan404 »

jackal wrote: Wed Sep 04, 2019 14:48 So you're saying there is a weaving issue but it doesn't actually cause congestion? And if it doesn't cause congestion why would you even consider closing J13 nb? I don't really follow.

A common solution to weaving is provision of an additional lane (that's one thing DMRB is not wrong about) so combined with sheer volumes it seems a no brainer.
This is not an ordinary weaving problem.

An ordinary weaving problem would be that you have traffic joining at J14 and traffic leaving at J13 both fighting for space in lane one at the same point. It is clear how widening helps with this.

In this situation we will have traffic leaving the M27 westbound having to make three lane changes over a very short distance, crossing over both fast and slow traffic joining from the M27 eastbound. On a normal D4/M some traffic may need to make that many lane changes over less than a mile, but never all of it and rarely does it involve crossing such a varied and dense stream of traffic. It is not a matter of congestion but safety. I'm struggling to visualise how widening would help with this as the merging area is already as long as it can be.

I don't doubt for a moment that the improved road will open like this and it will flow OK, it will just be far from ideal. Like so much of the motorway network.
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Re: M3 junctions 9 to 14: smart motorway

Post by mikehindsonevans »

jackal wrote: Wed Sep 04, 2019 14:48
Johnathan404 wrote: Wed Sep 04, 2019 13:52
jackal wrote: Wed Sep 04, 2019 13:39 In traffic terms they should add a fifth lane northbound at J14-13. They are presumably not doing this as there is still uncertainty about D5 ALR. M25 J15-16 is supposed to be the testbed but has slipped back to RIS2.
I appreciate you've got the figures but in practical terms I'm not sure why that would be needed. The congestion there is frequent but is always caused by traffic trying to pile into three lanes to get through J13, plus HGVs slowing down to climb the hill immediately beyond J13.

Ideally the exit at J13 northbound would be closed, or at least made accessible to traffic coming from the M27 eastbound only. The weaving there is only going to get worse. The north-facing onslip ought to be a lot longer too, as there isn't much room to build up speed.
So you're saying the cause of congestion is the three lane bottleneck and hill, not the weaving? But if the weaving doesn't cause congestion why would you even consider closing J13 nb? I don't really follow.

A common solution to weaving is provision of an additional lane (that's one thing DMRB is not wrong about) so combined with sheer volumes it seems a no brainer.
Just expanding this for a moment. Boy, am I glad that I no longer live in Chandler's Ford!

Closing M3j13NB to traffic from eastbound would drive that traffic off at M27j5 (Airport) - a junction already under stress and that is before the houses on Stoneham Park are fully occupied. The queues would go back past Hedge End.

Oh, hang on - they already do!

Secondly. What happened to the plan (in the 2005 long-term plan for the M3) which planned a 4th (crawler and j10 exit) lane up through Twyford Down from M3J11NB?

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Re: M3 junctions 9 to 14: smart motorway

Post by Patrick Harper »

Johnathan404 wrote: Wed Sep 04, 2019 13:52You're deep in to fantasy territory there. There is no plan to widen J6-8, nor is there any need to do it. Congestion there is (was?) caused by Black Dam Roundabout.
Realising the M3 J13 layout, I retract the comment.
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