M3 Junction 9 Improvements

[Bryn666]

My initial thought was that this could end up being worse than a delay. But then I remembered that the latest design already had the M3 and A34 merging into only three lanes, so maybe four lanes isn't as essential as it seems.

With 3 lanes I'd say it will be a bit slow at peak times no doubt due to how the flows are spat into the merge but 4 into 3 merges with a tiger tail lane gain are hardly rare. If they use the SM hiatus as reason to can this then we might as well pack up and go home. The safety benefits of the free-flow and separation of movements here outweigh the capacity constraint from the SM not happening.

[A303Chris]

My initial thought was that this could end up being worse than a delay. But then I remembered that the latest design already had the M3 and A34 merging into only three lanes, so maybe four lanes isn't as essential as it seems.

With 3 lanes I'd say it will be a bit slow at peak times no doubt due to how the flows are spat into the merge but 4 into 3 merges with a tiger tail lane gain are hardly rare. If they use the SM hiatus as reason to can this then we might as well pack up and go home. The safety benefits of the free-flow and separation of movements here outweigh the capacity constraint from the SM not happening.

Fully agree, my experiences of the junction, which I have to say is mainly staying on the M3, is queuing at the lights on the northbound exit slip and queuing on the A34 southbound approach. The two to three lanes on the southbound entry very rarely causes a queue, as southbound speeds are constrained with it being only D2M.

My biggest gripe is the lane drop northbound is probably the worst signed lane drop on the strategic highway network for such an important junction.

There is no one mile ADS, the half mile is so small it often gets obscured by HGV's

The final ADS is no better as well.

The number of times I see vehicles in lane 2 and lane 3 that do not know the road diving across at the last minute is significant. Why it is not signed by ganteries is beyond me.

[Bryn666]

My initial thought was that this could end up being worse than a delay. But then I remembered that the latest design already had the M3 and A34 merging into only three lanes, so maybe four lanes isn't as essential as it seems.

With 3 lanes I'd say it will be a bit slow at peak times no doubt due to how the flows are spat into the merge but 4 into 3 merges with a tiger tail lane gain are hardly rare. If they use the SM hiatus as reason to can this then we might as well pack up and go home. The safety benefits of the free-flow and separation of movements here outweigh the capacity constraint from the SM not happening.

Fully agree, my experiences of the junction, which I have to say is mainly staying on the M3, is queuing at the lights on the northbound exit slip and queuing on the A34 southbound approach. The two to three lanes on the southbound entry very rarely causes a queue, as southbound speeds are constrained with it being only D2M.

My biggest gripe is the lane drop northbound is probably the worst signed lane drop on the strategic highway network for such an important junction.

There is no one mile ADS, the half mile is so small it often gets obscured by HGV's

The final ADS is no better as well.

The number of times I see vehicles in lane 2 and lane 3 that do not know the road diving across at the last minute is significant. Why it is not signed by ganteries is beyond me.

90s cost cutting. M65 J6 should have had gantries too but got similar post mounted signs. J9 on the other hand has a gantry, being from the 80s. Luckily it's not as busy.

I can't wait to see the outrage when someone puts gantries through Twyford Down though

[Fluid Dynamics]

With 3 lanes I'd say it will be a bit slow at peak times no doubt due to how the flows are spat into the merge but 4 into 3 merges with a tiger tail lane gain are hardly rare. If they use the SM hiatus as reason to can this then we might as well pack up and go home. The safety benefits of the free-flow and separation of movements here outweigh the capacity constraint from the SM not happening.

Fully agree, my experiences of the junction, which I have to say is mainly staying on the M3, is queuing at the lights on the northbound exit slip and queuing on the A34 southbound approach. The two to three lanes on the southbound entry very rarely causes a queue, as southbound speeds are constrained with it being only D2M.

My biggest gripe is the lane drop northbound is probably the worst signed lane drop on the strategic highway network for such an important junction.

There is no one mile ADS, the half mile is so small it often gets obscured by HGV's

The final ADS is no better as well.

The number of times I see vehicles in lane 2 and lane 3 that do not know the road diving across at the last minute is significant. Why it is not signed by ganteries is beyond me.

90s cost cutting. M65 J6 should have had gantries too but got similar post mounted signs. J9 on the other hand has a gantry, being from the 80s. Luckily it's not as busy.

I can't wait to see the outrage when someone puts gantries through Twyford Down though

Minor point, but I'm pretty sure the sign format dates back to the '80s from the 8-9 extension rather than 90's with the Twyford Down scheme. Remember south of J9 towards J10 was build as part of the same scheme as j8-J9 (including Spitfire Bridge and the A31 parallel feeder road, which in part took over the old bypass route) but remained as the A33 and ending spontaneously close to what is now J10 with the third lane temporary covered over in parts awaiting the later Twyford Down scheme. The route of the road at J10 took a more westerly route through what in now the P&R.

[jnty]

The final ADS is no better as well.

I hate lane signs which indicate based on the number of lanes ahead, rather than the number of lanes at the point the sign is seen. It's not so bad here, but especially on the approach to roundabouts it adds cognitive load trying to work out which lanes now will turn into the lanes on the sign. If they really want to sign the lanes ahead in advance could they not put in a little illustrative dotted line somewhere to illustrate where the new lane is appearing?

[darkcape]

I can't wait to see the outrage when someone puts gantries through Twyford Down though

Paint all the gantries beige?

[Chris5156]

The final ADS is no better as well.

I hate lane signs which indicate based on the number of lanes ahead, rather than the number of lanes at the point the sign is seen. It's not so bad here, but especially on the approach to roundabouts it adds cognitive load trying to work out which lanes now will turn into the lanes on the sign. If they really want to sign the lanes ahead in advance could they not put in a little illustrative dotted line somewhere to illustrate where the new lane is appearing?

I agree. It’s possible to show arrows branching off each other, which is all that’s needed. Failing that the sign should surely match the lanes on the road at the point the sign is located.

[Paul7755]

My initial thought was that this could end up being worse than a delay. But then I remembered that the latest design already had the M3 and A34 merging into only three lanes, so maybe four lanes isn't as essential as it seems.

With 3 lanes I'd say it will be a bit slow at peak times no doubt due to how the flows are spat into the merge but 4 into 3 merges with a tiger tail lane gain are hardly rare. If they use the SM hiatus as reason to can this then we might as well pack up and go home. The safety benefits of the free-flow and separation of movements here outweigh the capacity constraint from the SM not happening.

Is it possible, if the eventual layout is built as drawn, that at busy times people coming down the A34 will suss it out and use the off slip route towards Winnal roundabout and then rejoin the M3 down the southbound on slip that becomes lane 1 of 4?

[Bryn666]

My initial thought was that this could end up being worse than a delay. But then I remembered that the latest design already had the M3 and A34 merging into only three lanes, so maybe four lanes isn't as essential as it seems.

With 3 lanes I'd say it will be a bit slow at peak times no doubt due to how the flows are spat into the merge but 4 into 3 merges with a tiger tail lane gain are hardly rare. If they use the SM hiatus as reason to can this then we might as well pack up and go home. The safety benefits of the free-flow and separation of movements here outweigh the capacity constraint from the SM not happening.

Is it possible, if the eventual layout is built as drawn, that at busy times people coming down the A34 will suss it out and use the off slip route towards Winnal roundabout and then rejoin the M3 down the southbound on slip that becomes lane 1 of 4?

Possible but I think there'd be little advantage to doing so.

[jackal]

A silver lining of the ALR freeze is that, with only three lanes in each direction under the J9 bridges, they could potentially save the significant cost of replacing them.

[SO53]

News about further changes to the design and new public engagement events posted on the National Highways website:

https://nationalhighways.co.uk/our-road ... rovements/

In essence some additional cycle lane provision, a subway for NMU's to avoid crossing one of the roundabouts and an increase in length to the southbound M3 slip road (but the one from Winnall roundabout as opposed to the one from the A34). But I haven't read the full article in detail.

[A307Patrick]

I see they are replacing the central barrier south of j9 to the M27. The signs say these works will take around a year to complete, which seems a long time. I assume this will this form part of the plan to convert this section to a smart motorway if/when that happens?

[jackal]

^ Yep.

I've been trying to work out the arrangement for the A34 merge/diverge now ALR has been dropped. The consultation page is not very clear about this. The best image is this, facing south:



It seems southbound there will be a long tigertail - you can just about see the tigertail ending at the top of the image, presumably as a lane gain, with roundabout traffic subsequently joining with a conventional merge (rather than lane gain).

Northbound will have a four-lane approach to the diverge with a 2+2 split, but you can't see where the fourth lane starts.

[jackal]

The scheme took a step forward today as it was accepted for examination. The application documents have accordingly been published by PINS, with the funding statement indicating "a most-likely estimate of £215 million, including allowances for risk and inflation at the date of application".

Here's the general arrangement: https://infrastructure.planninginspecto ... 0Plans.pdf

It's basically the same as previously shown, though the full detail of the merge/diverge arrangement is now apparent.

I still can't see how the A33/M3 northbound access can be important enough to get a filter to bypass the main roundabout, but so unimportant that NH can plonk another roundabout on it purely to serve their compound.

But overall it's a very good design that finally sorts out the A34 and A33.

[ChrisH]

The scheme took a step forward today as it was accepted for examination. The application documents have accordingly been published by PINS, with the funding statement indicating "a most-likely estimate of £215 million, including allowances for risk and inflation at the date of application".

Here's the general arrangement: https://infrastructure.planninginspecto ... 0Plans.pdf

It's basically the same as previously shown, though the full detail of the merge/diverge arrangement is now apparent.

I still can't see how the A33/M3 northbound access can be important enough to get a filter to bypass the main roundabout, but so unimportant that NH can plonk another roundabout on it purely to serve their compound.

But overall it's a very good design that finally sorts out the A34 and A33.

Aside from the slight roundabout-itis which afflicts all schemes, this is really very good. Clever way to solve the A33 access with the extra link. I also think the active travel facilities are some of the best I've seen on a scheme like this: plenty of high quality grade separated routes with clear sightlines through underpasses.

[A303Chris]

Good scheme but why keep the verge mounted 1 mile and 1/2 mile ADS signs on the northbound approach. Surely verge mounted gantries would be better.

[RichardA35]

Good scheme but why keep the verge mounted 1 mile and 1/2 mile ADS signs on the northbound approach. Surely verge mounted gantries would be better.

There isn't currently a 1 mile ADS for this junction. Both look like new signs which will have a different legend with the changed junction layout.

[jackal]

The Planning Inspectorate sent the Recommendation Report on 16 Feb. The Secretary of State has 3 months to make a decision (or extend their own deadline). "A positive decision will allow construction to start in January 2025 and be completed in 2027."

https://www.hampshirechronicle.co.uk/ne ... n-9-plans/

[Bryn666]

The Planning Inspectorate sent the Recommendation Report on 16 Feb. The Secretary of State has 3 months to make a decision (or extend their own deadline). "A positive decision will allow construction to start in January 2025 and be completed in 2027."

https://www.hampshirechronicle.co.uk/ne ... n-9-plans/

Is Mark Harper actually capable of holding a pen and signing his name or is this doomed to fall before the sword of the election?

[jervi]

Looks like Hampshire CC are waiting on knowing the go-ahead on this scheme before reworking the "car and horse junction" just up the A33 https://www.hants.gov.uk/transport/tran ... provements