M3 junctions 9 to 14: smart motorway

[jackal]

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.

As you initially said, the weaving is between traffic joining at J14 and traffic leaving at J13. M27 wb traffic that's heading up the M3 (i.e. the vast majority of it) just stays right. It's a pretty standard weaving situation and the standard solution of an extra lane would help by reducing traffic per lane and with it the intensity of the weaving.

[Johnathan404]

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.

Obviously it's never going to happen and I wouldn't suggest otherwise for a moment, but seeing as M3 J13 to M27 eastbound traffic has to use the back roads and cannot use the motorway, there is already a case for improving the Chestnut Avenue corridor and that awful mini roundabout. In an ideal country that road would have been upgraded before the retail parks opened.

It would make more sense for a fantasy road like that to be carrying traffic in both directions, rather than westbound traffic having to play Frogger with two busy lanes of M3.

[Richardf]

When I read this thread my heart sank. I use this section quite often and find it an uncomfortable experience with the standard motorway configuration, losing the hard shoulder could make the experience worse. I remember the old A33 days, when the road felt very claustrophobic. This is going back to those days, only multiplied!

With both this scheme and the J9 works set to go on at the same time, it sounds like the M3 will be a road to avoid for the duration, just as the eastern M27 is now.

[jackal]

Consultation on variable speed limits:

https://highwaysengland.citizenspace.co ... -motorway/

[J6onM27]

Looks like the preparation work is underway, the cones and yellow triffids have appeared.

https://highwaysengland.co.uk/our-work/ ... -motorway/

[Vierwielen]

Will the junction where the A34 joins the M3 be part of J9 or will it become J8a?

[Chris5156]

Will the junction where the A34 joins the M3 be part of J9 or will it become J8a?

I don't think any decision has been taken, but the junction upgrade isn't part of this scheme anyway - it's currently due to start on site in 2023, around the time the Smart Motorway work finishes.

[jackal]

9 and 9a would arguably be more logical

[Bryn666]

9 and 9a would arguably be more logical

Agreed - which means it won't happen...

I'd also make the old junction 9A, and the strategically more important direct A34 links 9. Far too often we get this the wrong way around, which would mean the northbound junction order would end up as 10, 9, 9A, 8.

... any second now we'll hear how km based exit numbering is much better because having J102A and J102B (because they'd both be within km 102) is somehow more memorable than J9 and J9A

[Herned]

9 and 9a would arguably be more logical

Agreed - which means it won't happen...

I'd also make the old junction 9A, and the strategically more important direct A34 links 9. Far too often we get this the wrong way around, which would mean the northbound junction order would end up as 10, 9, 9A, 8.

... any second now we'll hear how km based exit numbering is much better because having J102A and J102B (because they'd both be within km 102) is somehow more memorable than J9 and J9A

Junction 102.3 and 102.8 surely?

[Bryn666]

9 and 9a would arguably be more logical

Agreed - which means it won't happen...

I'd also make the old junction 9A, and the strategically more important direct A34 links 9. Far too often we get this the wrong way around, which would mean the northbound junction order would end up as 10, 9, 9A, 8.

... any second now we'll hear how km based exit numbering is much better because having J102A and J102B (because they'd both be within km 102) is somehow more memorable than J9 and J9A

Junction 102.3 and 102.8 surely?

Every international distance based system I'm aware of uses letter suffices for all junctions within the same km.

France, which is sequential, uses decimal points for new junctions and letters for multiple exits within the same complex, e.g. 15.1 for a new junction and 16a and 16b for a cloverleaf.

[Vierwielen]

9 and 9a would arguably be more logical

No, because this would mean renaming J9 as J9A. It might be more logical to name the new junction J9A and while the old J9 becomes J9B.

I would of course have no objection to the junctions becoming J100 (new M3 slip-road, northern access), J102 (new A34 slip roads - northern access) and J103 (existing M3 southern access).

[Herned]

Every international distance based system I'm aware of uses letter suffices for all junctions within the same km.

France, which is sequential, uses decimal points for new junctions and letters for multiple exits within the same complex, e.g. 15.1 for a new junction and 16a and 16b for a cloverleaf.

I should have added a smiley, I didn't know anywhere used decimals for junctions, I have only ever come across a's and b's with distance-based numbering

[ais523]

IIRC there are actual rules for this, so if you were leaving the old junction number alone, the new one would have to be either 8A or 9i. (I don't think the lowercase-Roman-numeral suffixes have ever been used? Also, I'm not confident I remember the rules for using them properly.)

[A303Chris]

Anyone know the latest on this. For the last 6 weeks temporary variable speed limit cameras have been erected along the section, with signs saying "Camera Not in Use", with the hard shoulder closed off.

During the evenings I have used it, it seems to be down to one lane both ways between 14 and 11. It looks like major works, but has it been delayed as the M27 Smartification works j4 to J11 are significantly over running

[Bryn666]

I thought this had got caught up in the smart motorway hullabaloo?

[Ben302]

Remember back when this was the A33 being converted to M3, didn't expect to be smartified 30 years after the mammoth roadworks undertaken there in the early 90's. Hope they put it off until the M27 works are done

[KeithW]

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?

Mike

The outcry over digging the cutting means no government is likely to put forward take that option.

[J6onM27]

Although smartification is on hold they are still going ahead with putting a concrete barrier central reservation works. Source - Highways magazine.

Anyone know the latest on this. For the last 6 weeks temporary variable speed limit cameras have been erected along the section, with signs saying "Camera Not in Use", with the hard shoulder closed off.

During the evenings I have used it, it seems to be down to one lane both ways between 14 and 11. It looks like major works, but has it been delayed as the M27 Smartification works j4 to J11 are significantly over running

[Gaz909909]

Yes, that's right. It seems they are doing as much as they can without the M3 actually being "smart".

https://www.hampshirechronicle.co.uk/ne ... rk-paused/