M3 Junction 9 Improvements

The study of British and Irish roads - their construction, numbering, history, mapping, past and future official roads proposals and general roads musings.

There is a separate forum for Street Furniture (traffic lights, street lights, road signs etc).

Registered users get access to other forums including discussions about other forms of transport, driving, fantasy roads and wishlists, and roads quizzes.

Moderator: Site Management Team

Post Reply
Herned
Member
Posts: 826
Joined: Thu Jul 20, 2017 09:15

Re: M3 Junction 9 Improvements

Post by Herned » Thu May 27, 2021 13:45

jackal wrote:
Thu May 27, 2021 12:39
Yes, there is a national cycle route running northeasterly through the junction, hence the spiral. My point is that the new NMU route running northwest from the junction to Kings Worthy is marked as footpath only when it would be perfect for cyclists.
Oh I missed that, that does look odd to only be a footpath. Can they get away with tighter corners or narrower bridges perhaps?

User avatar
Bryn666
Member
Posts: 31249
Joined: Thu Jun 20, 2002 20:54

Re: M3 Junction 9 Improvements

Post by Bryn666 » Thu May 27, 2021 14:00

Herned wrote:
Thu May 27, 2021 13:45
jackal wrote:
Thu May 27, 2021 12:39
Yes, there is a national cycle route running northeasterly through the junction, hence the spiral. My point is that the new NMU route running northwest from the junction to Kings Worthy is marked as footpath only when it would be perfect for cyclists.
Oh I missed that, that does look odd to only be a footpath. Can they get away with tighter corners or narrower bridges perhaps?
There are supposedly stringent DMRB standards for cycleways (they're naturally overspecc'd, assuming cyclists need similar radii to HGVs and the like), no doubt they're trying to value engineer it out. Worth pointing out that this needs to be a cycleway.
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

User avatar
jackal
Member
Posts: 6281
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: M3 Junction 9 Improvements

Post by jackal » Thu May 27, 2021 14:51

Looking at traffic counts the downgrade (compared to the previous design) to three lanes southbound through J9 looks a retrograde measure. This section is projected for 121k AADT on opening, which is overcapacity for three lanes.

Furthermore, 58k merging from the A34 gets only a single lane gain (plus tigertail), while the onslip from J9 gets a lane gain despite only have 9k. The previous design of a double lane gain for the A34 was far preferable. The M3 and A34 north of the junction have almost identical volumes and should get equal priority, i.e., 2+2=4.

M3 J9 2026 - Copy.JPG

(I deducted slip volumes from mainline volumes to get intra-junction volumes.)

User avatar
Bryn666
Member
Posts: 31249
Joined: Thu Jun 20, 2002 20:54

Re: M3 Junction 9 Improvements

Post by Bryn666 » Thu May 27, 2021 15:36

jackal wrote:
Thu May 27, 2021 14:51
Looking at traffic counts the downgrade (compared to the previous design) to three lanes southbound through J9 looks a retrograde measure. This section is projected for 121k AADT on opening, which is overcapacity for three lanes.

Furthermore, 58k merging from the A34 gets only a single lane gain (plus tigertail), while the onslip from J9 gets a lane gain despite only have 9k. The previous design of a double lane gain for the A34 was far preferable. The M3 and A34 north of the junction have almost identical volumes and should get equal priority, i.e., 2+2=4.


M3 J9 2026 - Copy.JPG


(I deducted slip volumes from mainline volumes to get intra-junction volumes.)
Yes, on balance I agree again (!) - 2+2 does seem more logical, especially given the existing roundabout will be quiet in comparison. This goes back to my comments (threads passim) that HE have no idea how merges and diverges work.
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

mikehindsonevans
Member
Posts: 1230
Joined: Tue Dec 06, 2016 11:44
Location: Cheshire, but working week time in Cambridge

Re: M3 Junction 9 Improvements

Post by mikehindsonevans » Sat May 29, 2021 06:18

So glad that we now live in Cheshire, so I shall only pass the Winnall junction every three months and usually at night.
Mike Hindson-Evans.
Never argue with a conspiracy theorist.
They will drag you down to their level and beat you with experience.

JRN
Member
Posts: 67
Joined: Sun May 16, 2021 20:11

Re: M3 Junction 9 Improvements

Post by JRN » Wed Jun 02, 2021 19:00

Bryn666 wrote:
Thu May 27, 2021 15:36
jackal wrote:
Thu May 27, 2021 14:51
Looking at traffic counts the downgrade (compared to the previous design) to three lanes southbound through J9 looks a retrograde measure. This section is projected for 121k AADT on opening, which is overcapacity for three lanes.

Furthermore, 58k merging from the A34 gets only a single lane gain (plus tigertail), while the onslip from J9 gets a lane gain despite only have 9k. The previous design of a double lane gain for the A34 was far preferable. The M3 and A34 north of the junction have almost identical volumes and should get equal priority, i.e., 2+2=4.


M3 J9 2026 - Copy.JPG


(I deducted slip volumes from mainline volumes to get intra-junction volumes.)
Yes, on balance I agree again (!) - 2+2 does seem more logical, especially given the existing roundabout will be quiet in comparison. This goes back to my comments (threads passim) that HE have no idea how merges and diverges work.
Agreed. Though looking at the 3D model on the consultation doc, it looks like the merge in of the offside lane from the A34 (the lane that *would* be lane no. 2 were the M3 opened to D4M at this point) happens in between the north and south bridges of the roundabout interchange. Assuming both bridges are the same span, there is likely room for a full D4M layout here.

(Not that it really matters as you could always squeeze the HS a bit, and this section will be the northern terminus of a Smart Motorway with variable speed limits by the time it opens.)

Hopefully they will fix the layout with paint to give both lanes to the A34 and make the local traffic merge instead if the initial layout doesn't work.

User avatar
jackal
Member
Posts: 6281
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: M3 Junction 9 Improvements

Post by jackal » Thu Jun 03, 2021 11:44

JRN wrote:
Wed Jun 02, 2021 19:00
Hopefully they will fix the layout with paint to give both lanes to the A34 and make the local traffic merge instead if the initial layout doesn't work.
As Bryn has mentioned many times, HE aren't very good at making these sensible little optimisations. The initial layout is likely to stay a long time - so they need to get it right first time.

Peter Freeman
Member
Posts: 689
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: M3 Junction 9 Improvements

Post by Peter Freeman » Thu Jun 03, 2021 14:16

jackal wrote:
Thu May 27, 2021 10:24
- I'm not sure why they have changed to a two bridge roundabout (with new bridges) from the previously planned dumbbell. There will be a massive reduction in traffic due to M3-A34 traffic bypassing the roundabout, and the dumbbell is surely cheaper.
Agree, the two-bridge elevated roundabout is inappropriate. A dumbbell would be perfect here, and lower in cost, and safer.

However, it should not be as shown in the original proposal: the western roundabout should be complete rather than tear-dropped, as no traffic should have to cross the motorway and then come back over again in order to exit south-westwards. The tear-dropped eastern roundabout in the original scheme was OK, and under my suggestion, without interference from west-side traffic that has no business there, it would function better.

User avatar
JammyDodge
Member
Posts: 182
Joined: Sat Oct 13, 2018 13:17

Re: M3 Junction 9 Improvements

Post by JammyDodge » Thu Jun 03, 2021 16:09

Peter Freeman wrote:
Thu Jun 03, 2021 14:16
jackal wrote:
Thu May 27, 2021 10:24
- I'm not sure why they have changed to a two bridge roundabout (with new bridges) from the previously planned dumbbell. There will be a massive reduction in traffic due to M3-A34 traffic bypassing the roundabout, and the dumbbell is surely cheaper.
Agree, the two-bridge elevated roundabout is inappropriate. A dumbbell would be perfect here, and lower in cost, and safer.

However, it should not be as shown in the original proposal: the western roundabout should be complete rather than tear-dropped, as no traffic should have to cross the motorway and then come back over again in order to exit south-westwards. The tear-dropped eastern roundabout in the original scheme was OK, and under my suggestion, without interference from west-side traffic that has no business there, it would function better.
The reason they replaced the dumbell is because they have added the A33 directly into the roundabout. The new 2-bridge design is larger than the dumbell, but smaller than the existing roundabout. There is also free flowing left turn onto the A33 from Easton Lane. Sadly there isn't too much space to retain the original design with the A33 plugged into it

With the original design, there was no need for a complete roundabout on the dumbell as the only traffic the would have to traverse the entire way around would have been from the Highway Depot
Designing Tomorrow, Around the Past

Peter Freeman
Member
Posts: 689
Joined: Thu Aug 30, 2012 07:52
Location: M1-Exit E9 Melbourne Australia

Re: M3 Junction 9 Improvements

Post by Peter Freeman » Fri Jun 04, 2021 12:59

JammyDodge wrote:
Thu Jun 03, 2021 16:09
With the original design, there was no need for a complete roundabout on the dumbell as the only traffic the would have to traverse the entire way around would have been from the Highway Depot
Oops, sorry, I missed that in my quick re-skim of the thread - I thought a two-way road came in there.

Even so, I prefer the dumbbell (tear-dropped). The low capacity shouldn't be a problem here. Smaller-scale roads are safer. Lower speeds make roundabout entry less intimidating, so signalisation can be avoided. By the way, I assume this new, smaller 2-bridge roundabout is not signalised ...?

User avatar
jackal
Member
Posts: 6281
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: M3 Junction 9 Improvements

Post by jackal » Fri Jun 04, 2021 13:22

Peter Freeman wrote:
Fri Jun 04, 2021 12:59
By the way, I assume this new, smaller 2-bridge roundabout is not signalised ...?
Correct. I was so impressed to see signals actually removed when they would no longer be needed that I didn't bother to complain about the two-bridge rbt when I completed the form. Technically, yes, I agree a dumbbell is a bit more cost effective, but it seemed potentially counterproductive to complain about an aspect of the design that gets so much right. (I did complain about the three lane southbound M3, HE depot rbt, and lack of cycleway towards Kings Worthy.)

User avatar
JammyDodge
Member
Posts: 182
Joined: Sat Oct 13, 2018 13:17

Re: M3 Junction 9 Improvements

Post by JammyDodge » Fri Jun 04, 2021 14:59

I have finally had time to send HE a comment and this is what I told them I had concerns over:

1) The M3/A34 merge should be 4 lanes in total, rather than 4 merging into 3. This is supported by your stated traffic flows now, with the M3 and A34 having roughly the same traffic flows. The lane gane south of Junction 9, from the roundabout would not be required, instead just merging into a 4 lane M3

2) The access to the Highways depot on the future A33 would be better served by a simple T-Junction with a turn lane provided northbound

3) The freeflow link between the M3 south slip and the A272 should have a form of physical segregation between the link and the roundabout, rather than hatching. This link should also have an appropriate merge onto the A272, rather than a give-way.
Designing Tomorrow, Around the Past

User avatar
JammyDodge
Member
Posts: 182
Joined: Sat Oct 13, 2018 13:17

Re: M3 Junction 9 Improvements

Post by JammyDodge » Tue Jun 15, 2021 17:12

HE have just sent me a response to my comments:

Thank you for the feedback provided. We’ll ensure that it is recorded as part of the consultation process. Please see below our responses to the points you have raised.

1) The M3/A34 merge should be 4 lanes in total, rather than 4 merging into 3. This is supported by your stated traffic flows now, with the M3 and A34 having roughly the same traffic flows. The lane gain south of Junction 9, from the roundabout would not be required, instead just merging into a 4 lane M3

The current scheme is based on the modelling forecasts and Motorway upgrade scheme shown in the Regional Developments Plan. Predicted economic growth is also taken into account, with the scheme designed to cater for the predicted increased traffic flow like to happen over the next twenty years.


2) The access to the Highways depot on the future A33 would be better served by a simple T-Junction with a turn lane provided northbound

We have discussed the changes to the Highways England maintenance depot team. The proposed junction layout was agreed as the best option going forward with the existing exit to the rear of the depot being removed.

3) The freeflow link between the M3 south slip and the A272 should have a form of physical segregation between the link and the roundabout, rather than hatching. This link should also have an appropriate merge onto the A272, rather than a give-way.

The current proposal meets current design standards as these recommend a give-way function. Introducing a physical segregation between the roundabout and the A272, would introduce the requirement for all of the approaches and exits on the roundabout to be lit.
Designing Tomorrow, Around the Past

User avatar
jervi
Member
Posts: 1213
Joined: Thu Aug 17, 2017 16:29
Location: Lincoln / Haywards Heath

Re: M3 Junction 9 Improvements

Post by jervi » Tue Jun 15, 2021 22:24

JammyDodge wrote:
Tue Jun 15, 2021 17:12
HE have just sent me a response to my comments:

Thank you for the feedback provided. We’ll ensure that it is recorded as part of the consultation process. Please see below our responses to the points you have raised.

1) The M3/A34 merge should be 4 lanes in total, rather than 4 merging into 3. This is supported by your stated traffic flows now, with the M3 and A34 having roughly the same traffic flows. The lane gain south of Junction 9, from the roundabout would not be required, instead just merging into a 4 lane M3

The current scheme is based on the modelling forecasts and Motorway upgrade scheme shown in the Regional Developments Plan. Predicted economic growth is also taken into account, with the scheme designed to cater for the predicted increased traffic flow like to happen over the next twenty years.
They planning for the traffic flows 20 years in advance! I'm fairly certain the road layout would need to be repainted at least once between completion and 2041, if they design it with both layouts in mind it could accommodate a 2 lane gain + 1 lane merge now and then could cheaply changed to 1 lane gain + 1 lane gain at a later date if the traffic flows changed enough to warrant it.

User avatar
Chris5156
Member
Posts: 14697
Joined: Thu Sep 06, 2001 21:50
Location: Hampshire
Contact:

Re: M3 Junction 9 Improvements

Post by Chris5156 » Wed Jun 16, 2021 01:18

Thanks for posting the replies you got - not really surprising to see that they are all a bit "computer says no".
JammyDodge wrote:
Tue Jun 15, 2021 17:12
Introducing a physical segregation between the roundabout and the A272, would introduce the requirement for all of the approaches and exits on the roundabout to be lit.
Can any of our professionals shed any light on this bizarre statement?

User avatar
JammyDodge
Member
Posts: 182
Joined: Sat Oct 13, 2018 13:17

Re: M3 Junction 9 Improvements

Post by JammyDodge » Wed Jun 16, 2021 22:42

Chris5156 wrote:
Wed Jun 16, 2021 01:18
Thanks for posting the replies you got - not really surprising to see that they are all a bit "computer says no".
JammyDodge wrote:
Tue Jun 15, 2021 17:12
Introducing a physical segregation between the roundabout and the A272, would introduce the requirement for all of the approaches and exits on the roundabout to be lit.
Can any of our professionals shed any light on this bizarre statement?
I did think it was a bit odd. As it would just be a merge/diverge. I don't know why you would require lighting for it
Designing Tomorrow, Around the Past

User avatar
Bryn666
Member
Posts: 31249
Joined: Thu Jun 20, 2002 20:54

Re: M3 Junction 9 Improvements

Post by Bryn666 » Thu Jun 17, 2021 00:09

Chris5156 wrote:
Wed Jun 16, 2021 01:18
Thanks for posting the replies you got - not really surprising to see that they are all a bit "computer says no".
JammyDodge wrote:
Tue Jun 15, 2021 17:12
Introducing a physical segregation between the roundabout and the A272, would introduce the requirement for all of the approaches and exits on the roundabout to be lit.
Can any of our professionals shed any light on this bizarre statement?
One of many stupidities of the DMRB, I'm afraid. The second you introduce kerb islands they become hazards so have to be lit in a way that paint alone does not, despite the rest of the world managing quite well with unlit roads.
Bryn
Traffic/Road Safety Dogsbody and General Grumpy Now-a-Thirtysomething Man
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/

SteveA30
Member
Posts: 5342
Joined: Fri May 06, 2005 12:52
Location: Dorset
Contact:

Re: M3 Junction 9 Improvements

Post by SteveA30 » Thu Jun 17, 2021 15:51

Sounds like DMRB needs to be revisited and in modern parlance, descoped, ie simplified. If a rule doesn't exist, there is no need to obey it.
Roads and holidays in the west, before motorways.
https://roadhog.shutterfly.com
http://holidayroads.webs.com/

Post Reply