M4 Junction 3 to 12 Smart Motorway

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
User avatar
Truvelo
Member
Posts: 17467
Joined: Wed May 29, 2002 21:10
Location: Staffordshire
Contact:

Re: M4 Junction 3 to 12 Smart Motorway

Post by Truvelo »

Doing away with the park and ride part of it would surely reduce the demand while achieving the desired effect of removing the bottleneck. It doesn't even need the equivalent westbound onslip.
How would you like your grade separations, Sir?
Big and complex.
User avatar
Bryn666
Elected Committee Member
Posts: 35754
Joined: Thu Jun 20, 2002 20:54
Contact:

Re: M4 Junction 3 to 12 Smart Motorway

Post by Bryn666 »

I can't see the suburbs being happy at thousands of vehicles being dumped off the M4 onto their local network.

If you build a J2A, it'd have to be for a transport interchange with the TfL rail systems.
Bryn
Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
User avatar
ManomayLR
Social Media Admin
Posts: 3331
Joined: Wed Aug 03, 2016 11:47
Location: London, UK

Re: M4 Junction 3 to 12 Smart Motorway

Post by ManomayLR »

Bryn666 wrote:I can't see the suburbs being happy at thousands of vehicles being dumped off the M4 onto their local network.

If you build a J2A, it'd have to be for a transport interchange with the TfL rail systems.
If there will be bottlenecks due to less lanes, building a new junction would cause even more issues in works. If bottlenecks build up to the SMART motorway section then VSL would be used.

Seeing as standard motorway MIDAS is used without VSL on the viaduct, why not fit in VSL? Would it be any great help?
Though roads may not put a smile on everyone's face, there is one road that always will: the road to home.
WHBM
Member
Posts: 9705
Joined: Thu Nov 30, 2006 18:01
Location: London

Re: M4 Junction 3 to 12 Smart Motorway

Post by WHBM »

Chris5156 wrote: It wouldn't have worked for several reasons. A few years ago another member had the same idea, and it turns out the Sabristi include someone who had actually investigated it at the time!
Well that saves me looking it up :) . We had looked at this Boston Manor one in the 1970s as part of a University study.

A further issue nowadays is the disparity in rail fares between London from the outer Underground points, and commuter stations on the national network beyond, and even a comparable disparity in station car park charges, means that outer Underground stations now are attractive to those, especially daily commuters, driving from places beyond the Underground, if only they can get parked. I believe Epping suffers particularly from this.
User avatar
Chris5156
Deputy Treasurer
Posts: 16908
Joined: Thu Sep 06, 2001 21:50
Location: Hampshire
Contact:

Re: M4 Junction 3 to 12 Smart Motorway

Post by Chris5156 »

WHBM wrote:
Chris5156 wrote: It wouldn't have worked for several reasons. A few years ago another member had the same idea, and it turns out the Sabristi include someone who had actually investigated it at the time!
Well that saves me looking it up :)
Happy to be of service! What amused me is that your post from 2010 starts with the phrase "we have discussed this before", so apparently it wasn't even new information back then.

Such things seem to be par for the course if you hang around on the same web forum for fifteen years or so :shock:
User avatar
ManomayLR
Social Media Admin
Posts: 3331
Joined: Wed Aug 03, 2016 11:47
Location: London, UK

Re: M4 Junction 3 to 12 Smart Motorway

Post by ManomayLR »

EpicChef wrote:
Bryn666 wrote:I can't see the suburbs being happy at thousands of vehicles being dumped off the M4 onto their local network.

If you build a J2A, it'd have to be for a transport interchange with the TfL rail systems.
If there will be bottlenecks due to less lanes, building a new junction would cause even more issues in works. If bottlenecks build up to the SMART motorway section then VSL would be used.

Seeing as standard motorway MIDAS is used without VSL on the viaduct, why not fit in VSL? Would it be any great help?
Any opinions on this?
Though roads may not put a smile on everyone's face, there is one road that always will: the road to home.
User avatar
jackal
Member
Posts: 7544
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: M4 Junction 3 to 12 Smart Motorway

Post by jackal »

Preparation works start in a week, with main construction in the Autumn:

http://roads.highways.gov.uk/projects/m ... -motorway/
User avatar
Bryn666
Elected Committee Member
Posts: 35754
Joined: Thu Jun 20, 2002 20:54
Contact:

Re: M4 Junction 3 to 12 Smart Motorway

Post by Bryn666 »

EpicChef wrote:
EpicChef wrote:
Bryn666 wrote:I can't see the suburbs being happy at thousands of vehicles being dumped off the M4 onto their local network.

If you build a J2A, it'd have to be for a transport interchange with the TfL rail systems.
If there will be bottlenecks due to less lanes, building a new junction would cause even more issues in works. If bottlenecks build up to the SMART motorway section then VSL would be used.

Seeing as standard motorway MIDAS is used without VSL on the viaduct, why not fit in VSL? Would it be any great help?
Any opinions on this?
No point as the viaduct is only 40 mph anyway.
Bryn
Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
WHBM
Member
Posts: 9705
Joined: Thu Nov 30, 2006 18:01
Location: London

Re: M4 Junction 3 to 12 Smart Motorway

Post by WHBM »

jackal wrote:Preparation works start in a week, with main construction in the Autumn:
A compound and some static plant is being put in place right now on the roundabout at J5 Langley.
User avatar
ManomayLR
Social Media Admin
Posts: 3331
Joined: Wed Aug 03, 2016 11:47
Location: London, UK

Re: M4 Junction 3 to 12 Smart Motorway

Post by ManomayLR »

Bryn666 wrote:
EpicChef wrote:
EpicChef wrote:If there will be bottlenecks due to less lanes, building a new junction would cause even more issues in works. If bottlenecks build up to the SMART motorway section then VSL would be used.

Seeing as standard motorway MIDAS is used without VSL on the viaduct, why not fit in VSL? Would it be any great help?
Any opinions on this?
No point as the viaduct is only 40 mph anyway.
VSL could be able to bring the viaduct speed limit back to 70 mph.
Though roads may not put a smile on everyone's face, there is one road that always will: the road to home.
User avatar
Bryn666
Elected Committee Member
Posts: 35754
Joined: Thu Jun 20, 2002 20:54
Contact:

Re: M4 Junction 3 to 12 Smart Motorway

Post by Bryn666 »

That is definitely not an option. The design speed of the viaduct is nowhere near 70. The curvature and lack of hard shoulder plus minimal merge lanes at the junctions rule out any higher speed limits.

40 is justified.
Bryn
Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.

Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
User avatar
A303Chris
Elected Committee Member
Posts: 3587
Joined: Mon Sep 20, 2004 14:01
Location: Reading

Re: M4 Junction 3 to 12 Smart Motorway

Post by A303Chris »

EpicChef wrote: VSL could be able to bring the viaduct speed limit back to 70 mph.
Viaduct was never 70mph , was always 50 mph reduced to 40mph when bus lane when in between J3 and the start of the viaduct in 1999 and speed limit was reduced to 50 mph between J4 and the viaduct. When speed limit was increase to 60mph between J4 and the viaduct (a much better compromise), the limit on the flyover remained at 40mph
The M25 - The road to nowhere
User avatar
ManomayLR
Social Media Admin
Posts: 3331
Joined: Wed Aug 03, 2016 11:47
Location: London, UK

Re: M4 Junction 3 to 12 Smart Motorway

Post by ManomayLR »

Bryn666 wrote:That is definitely not an option. The design speed of the viaduct is nowhere near 70. The curvature and lack of hard shoulder plus minimal merge lanes at the junctions rule out any higher speed limits.

40 is justified.

Makes sense-would they ever try to widen the viaduct to have D3M or at least D2M/D3 dynamic hard shoulder?

Why was the bus lane removed, why not "dynamic bus lane", a twist on dynamic hard shoulders?
Though roads may not put a smile on everyone's face, there is one road that always will: the road to home.
ais523
Member
Posts: 1139
Joined: Tue Sep 08, 2015 19:52
Location: Birmingham

Re: M4 Junction 3 to 12 Smart Motorway

Post by ais523 »

Having timed bus lanes is very common (i.e. the bus lane only exists at certain times of day, on certain days of the week). However, drivers often seem to have a tendency to avoid them even when they aren't active (perhaps out of habit from when they're active, or perhaps out of a desire not to worry about whether they're active).

I imagine a dynamic bus lane would cause similar amounts of confusion to DHSR, but possibly even worse.
Lewis1997
Member
Posts: 202
Joined: Mon Apr 03, 2017 22:53

Re: M4 Junction 3 to 12 Smart Motorway

Post by Lewis1997 »

Is there plans to do the smart motorway project in sections or as a whole?
WHBM
Member
Posts: 9705
Joined: Thu Nov 30, 2006 18:01
Location: London

Re: M4 Junction 3 to 12 Smart Motorway

Post by WHBM »

EpicChef wrote: Why was the bus lane removed
Because there were no buses on it. The one remaining bus service on the M4 at this point, the last vestige of the (generally empty) Airbus from Heathrow to London, had been withdrawn at the opening of the bus lane.
User avatar
ManomayLR
Social Media Admin
Posts: 3331
Joined: Wed Aug 03, 2016 11:47
Location: London, UK

Re: M4 Junction 3 to 12 Smart Motorway

Post by ManomayLR »

We have relatives whom we go to via the M4 from 4B from M25 to 10 for A329M. If the motorway were not to be renovated in sections we'd have 50 all the way till A329M. Also sometimes there's also a commute to Newbury, of which the majority would be 50. If the whole stretch were 50 instead of staged renovation it would be a massive bummer.
Though roads may not put a smile on everyone's face, there is one road that always will: the road to home.
WHBM
Member
Posts: 9705
Joined: Thu Nov 30, 2006 18:01
Location: London

Re: M4 Junction 3 to 12 Smart Motorway

Post by WHBM »

Major compound now established in the middle of the roundabout at J5 Langley, although it seems to have taken a couple of months to get it in place. Presumably for the widening of the M4 bridge. Main contractor is a Balfours-Vinci JV, although the actual works have been subcontracted out so far to a secondary civils contractor.
mikehindsonevans
Member
Posts: 1359
Joined: Tue Dec 06, 2016 11:44
Location: Cheshire, but working week time in Cambridge

Re: M4 Junction 3 to 12 Smart Motorway

Post by mikehindsonevans »

WHBM wrote:
EpicChef wrote: Why was the bus lane removed
Because there were no buses on it. The one remaining bus service on the M4 at this point, the last vestige of the (generally empty) Airbus from Heathrow to London, had been withdrawn at the opening of the bus lane.
The disruption caused by the M4 bus lane is reminiscent of the "experimental" right-hand turn lane implemented in the (?1980s?) for about a week up near Earls Court - it managed to stuff up traffic all the way back to Heston and incurred the wrath of the late Terry Wogan (amongst others). It is rumoured that the traffic planner responsible couldn't find his bicycle clips in a Halfords shop.
Mike Hindson-Evans.
Never argue with a conspiracy theorist.
They will drag you down to their level and beat you with experience.
User avatar
Truvelo
Member
Posts: 17467
Joined: Wed May 29, 2002 21:10
Location: Staffordshire
Contact:

Re: M4 Junction 3 to 12 Smart Motorway

Post by Truvelo »

Chris5156 wrote:
ChrisH wrote:
Truvelo wrote: Has anyone thought about a J2a with just west facing slips onto Boston Manor Road? There must surely be traffic from the west who's destination is near Brentford but either has to leave at J3 and negotiate miles of A4 or suffer the crush at the viaduct and leave at J2. A junction immediately west of the viaduct could solve many problems. Not only would it ease the crush but it could take some traffic off the viaduct.
I previously floated this idea at work as a revenue raiser. Build west-facing slips, a massive multi-storey car park and a link to Boston Manor station on the Piccadilly line. That way we'd raise revenue twice over :wink:
If you want to do that you can dig out the construction plans drawn up by the Department of the Environment in the mid-1970s. I have copies of them somewhere. They were going to build a surface car park but the idea was the same - drop the third lane of the M4 into a dedicated park and ride site next to the Piccadilly Line.

It wouldn't have worked for several reasons. A few years ago another member had the same idea, and it turns out the Sabristi include someone who had actually investigated it at the time!
Turns out the idea of a west facing junction at Boston Manor was resurrected in 1991. It was part of a study to improve traffic flow on the A4 and M4. Ideally the A4 between Heathrow and Brentford would be D3 with GSJs but the cost and the negative impact for local traffic movements ruled it out, a shame because traffic travelling between Central London and the airport wouldn't have to clog up the M4. Attention turned to the M4 lane drop where single lane slips at a new J2a would transfer traffic between the M4 and A4. The A4 between this new junction and Chiswick Roundabout would be D4 to cope with the additional traffic. The J2 westbound onslip would close as the 60m merge is insufficient. It also recommends closing the other west facing slip at J2 so all traffic from the west wanting the A406 would have to use the new junction. This would ensure the lane drop would work well and take enough traffic off the elevated M4 to prevent future queuing.

So the fear about the new junction dumping traffic on the local roads is now unfounded. Having direct slips to the A4 rather than just Boston Manor Road was a brilliant idea that like so many other schemes of its time failed to see the light of day.
How would you like your grade separations, Sir?
Big and complex.
Post Reply