A358 Taunton to Southfields

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
Chris5156
Member
Posts: 14618
Joined: Thu Sep 06, 2001 21:50
Location: Hampshire
Contact:

Re: A358 Taunton to Southfields

Post by Chris5156 » Thu Jun 27, 2019 19:07

I wonder if there's some thought at HE that a new junction on the M5 to create a free-flowing route is better split off into a separate, later scheme, either for budgetary reasons or political ones? I find it hard to see how an eventual A303 expressway could be considered complete if it just hit the existing roundabout under the M5 that is already signalised and is already badly congested.

The other vain hope is that someone at HE or DfT is having second third fourth fifth sixth seventh thoughts about the Blackdown Hills dualling and has gone lukewarm on the A358 scheme as a result. But I think that is highly unlikely at this stage, as much as it would be popular among Sabristi.

User avatar
jackal
Member
Posts: 6236
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: A358 Taunton to Southfields

Post by jackal » Thu Jun 27, 2019 19:08

According to the SAR the proposed J25 improvements are a dedicated left turn for A358 Toneway to M5 North and widening of the M5 sb offslip. With these improvements:
The LinSig analysis for 2038 shows DoS [degree of saturation] on the Toneway approach up to 91.5% which is just above the 90% recommended threshold, but with queues that can be accommodated within the link stacking capacity and with a delay per Passenger Car Unit (PCU) below of one minute. The queues that would develop on the gyratory lanes opposite the Toneway approach, the new A358 east approach and the M5 northbound off-slip exceed the link stacking capacities in the AM peak hour (and also in the PM peak hour with the exception of the gyratory lanes opposite the M5 northbound off-slip). These queues have the possibility of blocking upstream junctions and therefore affecting the overall operation of the roundabout.
Later on they say "The performance of the gyratory lanes might be further improved and mitigated with a more detailed signal analysis in later stages of the Scheme development (that is Project Control Framework (PCF) Stage 3)". So clearly the idea is to scrape together something that just about manages in theory (and probably not at all in practice).
roadtester wrote:
Thu Jun 27, 2019 17:04
Also, do we know the junction in the middle at Ash will be a GSJ?
Yes we do.

A weird feature of the proposal is that Southfields roundabout will be widened despite the cost saving efforts elsewhere and plans for the Ilminster bypass.

Richardf
Member
Posts: 1612
Joined: Wed Dec 06, 2006 10:19
Location: Dorchester
Contact:

Re: A358 Taunton to Southfields

Post by Richardf » Thu Jun 27, 2019 20:01

Not ideal, but if it gets the dualling done then that's better than not at all. Dualling the A358 is the priority. Freeflow links and GSJ''s can come later. Wouldn't be the first expressway built this way.
My latest Road Photos https://flic.kr/s/aHsktQHcMB

boliston
Member
Posts: 141
Joined: Wed Dec 10, 2014 19:43
Location: Taunton
Contact:

Re: A358 Taunton to Southfields

Post by boliston » Thu Jun 27, 2019 21:01

at least they are choosing the 'pink option' and have improved on it further by removing the extra pointless section of new road across existing open countryside - to me the newly announced route seems a good compromise and has least impact on the local area in terms of disruption - it's a nice simple upgrade which mainly respects the original alignment while taking through traffic out of the centre of henlade village

A320Driver
Member
Posts: 377
Joined: Fri Jun 24, 2005 19:11
Location: Leatherhead

Re: A358 Taunton to Southfields

Post by A320Driver » Thu Jun 27, 2019 21:58

Saddened but not surprised. They want to chuck strategic, regional and local traffic for Taunton into the J25 roundabout, it will snarl up on day 1 and traffic will queue back onto the A358.

There isn’t one mention of the word ‘expressway’ in the PRA document. This presents itself as a local rather than a strategic scheme, and won’t persuade me to use it over the Blackdown Hills route I’m afraid.
Free flow at Southfields and the M5 however, may have just tipped the balance.

Overall disappointing but as I say, not surprised really.
Formerly ‘guvvaA303’

User avatar
roadtester
Social Media Admin
Posts: 29107
Joined: Mon Mar 26, 2007 18:05
Location: Cambridgeshire

Re: A358 Taunton to Southfields

Post by roadtester » Thu Jun 27, 2019 22:06

A320Driver wrote:
Thu Jun 27, 2019 21:58
Saddened but not surprised. They want to chuck strategic, regional and local traffic for Taunton into the J25 roundabout, it will snarl up on day 1 and traffic will queue back onto the A358.

There isn’t one mention of the word ‘expressway’ in the PRA document. This presents itself as a local rather than a strategic scheme, and won’t persuade me to use it over the Blackdown Hills route I’m afraid.
Free flow at Southfields and the M5 however, may have just tipped the balance.

Overall disappointing but as I say, not surprised really.
Yes, that's the point - this is supposed to be the big picture solution to the difficulty of dualling the A303 through the Blackdown Hills, completing the A303 as an expressway route to the southwest. Linking across to the M5 here already seems like an cheapo option to doing the job properly by dualling the A303 all the way, so I thought this thing would at least be GSJed and future-proofed up to the eyeballs rather than, as seems to be the case, a how-little-can-we-get-away-with job!
Electrophorus Electricus

User avatar
Debaser
Member
Posts: 1929
Joined: Wed Sep 02, 2009 16:57

Re: A358 Taunton to Southfields

Post by Debaser » Fri Jun 28, 2019 06:11

Chris5156 wrote:
Thu Jun 27, 2019 19:07
I wonder if there's some thought at HE...
And that was your first mistake.😁

User avatar
RichardA35
Site Manager
Posts: 4608
Joined: Thu Jul 11, 2002 18:58
Location: Dorset

Re: A358 Taunton to Southfields

Post by RichardA35 » Fri Jun 28, 2019 08:27

Debaser wrote:
Fri Jun 28, 2019 06:11
Chris5156 wrote:
Thu Jun 27, 2019 19:07
I wonder if there's some thought at HE...
And that was your first mistake.😁
Exec Summary of A358 SAR wrote:"With updated Scheme cost estimates exceeding the stated range of £250m - £500m, further assessment and design work was undertaken to develop a modified option to reduce costs. The Pink Modified option emerged following substantiation that Junction A (connection to the M5 at Blackbrook), Junction B and the road in-between, could be removed from the Scheme. This made the Scheme more affordable whilst still delivering the RIS objectives. It also provided a solution that is sympathetic to the public’s concern raised about impact to the countryside and the open space."
&
"The BCRs in the current assessment for all the options, have reduced from
those reported in the Technical Appraisal Report, January 2018, due to:
 A switch from TEMPRO v7.0 to v7.2 was made in line with Department
for Transport (DfT) guidance. TEMPRO v7.2 provided lower overall traffic
growth in the south-west region
compared to TEMPRO v7.0. The BCRs
have been adversely affected by a combination of rising costs (that is,
Present Value of Costs- PVC)."
The Executive Summary of the SAR is a sorry tale of woe (and reminds me of Chichester). Essentially someone in HE/DfT land decided that a scheme of £250M was what was wanted here without any design or development work to refer to and irrespective of whether it met the needs and solved all the problems.
The scheme has now been heavily value managed back to the budget available which should be no surprise to anyone in the south west given how far away the region is from London.
I suppose a saving grace is that the additional long distance traffic that might switch from the M4 route will not materialise until the other A303 schemes (including Stonehenge) are complete at some uncertain date in the future.

User avatar
Debaser
Member
Posts: 1929
Joined: Wed Sep 02, 2009 16:57

Re: A358 Taunton to Southfields

Post by Debaser » Fri Jun 28, 2019 08:37

This is the tale of many RIS1 schemes. Where the scheme estimates have come from god knows, but the ones I've worked on they seem to have been less than is actually needed to provide a decent scheme, so they've all been value engineered to within an inch of being pointless. I've said it before, but HE saw a pot of gold bigger than they'd ever had before and their eyes got too big for their belly. 'Fewer schemes higher quality' should have been their mantra.

User avatar
AAndy
Member
Posts: 3438
Joined: Thu May 12, 2005 20:28

Re: A358 Taunton to Southfields

Post by AAndy » Fri Jun 28, 2019 08:45

To keep Taunton on one m5 junctio is strange...even little old bridgwater just up the road has 2.

User avatar
A303Chris
Elected Committee Member
Posts: 3178
Joined: Mon Sep 20, 2004 14:01
Location: Reading

Re: A358 Taunton to Southfields

Post by A303Chris » Fri Jun 28, 2019 11:13

I was just going to post this as it popped into my inbox, but what a disaster. Two at grade roundabouts at either end , which are already overloaded, again road improvements on the cheap. As with the A380 at Kingskerwell will it have a 50mph to reduce the costs even further. I do wonder if the costs have been reduced to pay for Stonehenge, which is only going up, up, up.

As has been said many times apart form holiday weekends the A303 through the Blackdown Hill is not that busy for a strategic route. If Devon's plan to provide a S/C online improvement with overtaking lanes of the A30 between the A303 junction and Honiton, you would only be looking at about 6 miles of old route. Given the existing distance, up to Taunton, it only usually takes me about 20 to 25 mins to do the 13 miles from the end of the Illminster bypass to Honiton anyway.
The M25 - The road to nowhere

User avatar
Peter350
Member
Posts: 713
Joined: Thu Jan 25, 2018 20:20
Location: Southampton

Re: A358 Taunton to Southfields

Post by Peter350 » Fri Jun 28, 2019 12:30

I’d be interested to know whether Exeter will still be signed on the A303 westbound exit at Southfields once this shambles of a project has been finished.

User avatar
Chris5156
Member
Posts: 14618
Joined: Thu Sep 06, 2001 21:50
Location: Hampshire
Contact:

Re: A358 Taunton to Southfields

Post by Chris5156 » Fri Jun 28, 2019 12:58

RichardA35 wrote:
Fri Jun 28, 2019 08:27
The Executive Summary of the SAR is a sorry tale of woe (and reminds me of Chichester). Essentially someone in HE/DfT land decided that a scheme of £250M was what was wanted here without any design or development work to refer to and irrespective of whether it met the needs and solved all the problems.
The scheme has now been heavily value managed back to the budget available which should be no surprise to anyone in the south west given how far away the region is from London.
Thanks for posting that, I hadn't seen it.

The result is, sadly, yet another road scheme that builds a decent road between terrible junctions.

User avatar
Norfolktolancashire
Member
Posts: 953
Joined: Tue Apr 17, 2007 22:34
Location: Cornwall

Re: A358 Taunton to Southfields

Post by Norfolktolancashire » Fri Jun 28, 2019 13:02

AAndy wrote:
Fri Jun 28, 2019 08:45
To keep Taunton on one m5 junctio is strange...even little old bridgwater just up the road has 2.
As a regular traveller past and into Taunton I have wondered this lack of a "west Taunton junction. With all the residential development around the town over the recent years the one junction is heavily overloaded.

SteveA30
Member
Posts: 5320
Joined: Fri May 06, 2005 12:52
Location: Dorset
Contact:

Re: A358 Taunton to Southfields

Post by SteveA30 » Fri Jun 28, 2019 14:20

Will the old A358 at Henlade still be a through route? Even with traffic calming and reducing the D2 to S2, it will soon become a rat run to the M5 n/bnd when there are huge summer queues at J25, forewarned by Satnav. Not s/bnd as there would be no advantage.
Also, it looks as if heading through Ilminster w/bnd will still be my route, as it is now.
Last edited by SteveA30 on Fri Jun 28, 2019 14:21, edited 1 time in total.
Roads and holidays in the west, before motorways.
https://roadhog.shutterfly.com
http://holidayroads.webs.com/

Herned
Member
Posts: 799
Joined: Thu Jul 20, 2017 09:15

Re: A358 Taunton to Southfields

Post by Herned » Fri Jun 28, 2019 14:21

Norfolktolancashire wrote:
Fri Jun 28, 2019 13:02
As a regular traveller past and into Taunton I have wondered this lack of a "west Taunton junction. With all the residential development around the town over the recent years the one junction is heavily overloaded.
Jct 26 is very useful for heading west for a lot of the town and is signed on the M5 for Taunton. And you can use the back road to the services as an unofficial junction, or so I've been told

User avatar
AAndy
Member
Posts: 3438
Joined: Thu May 12, 2005 20:28

Re: A358 Taunton to Southfields

Post by AAndy » Fri Jun 28, 2019 15:55

SteveA30 wrote:
Fri Jun 28, 2019 14:20
Will the old A358 at Henlade still be a through route? Even with traffic calming and reducing the D2 to S2, it will soon become a rat run to the M5 n/bnd when there are huge summer queues at J25, forewarned by Satnav. Not s/bnd as there would be no advantage.
Also, it looks as if heading through Ilminster w/bnd will still be my route, as it is now.
There are other routes which I use and always alternatives which have saved me from ever being in traffic jams.

I feel the reasons are political (and a particular party involved) as to why future proofed new roads are not being built.

A bit like the M4 relief road in South Wales.

A reason why these new roads are not being built seem to be some erroneous projections that traffic demand is going to reduce. Who is giving this advice and why arn't the predictions being questioned?

Richardf
Member
Posts: 1612
Joined: Wed Dec 06, 2006 10:19
Location: Dorchester
Contact:

Re: A358 Taunton to Southfields

Post by Richardf » Fri Jun 28, 2019 19:50

SteveA30 wrote:
Fri Jun 28, 2019 14:20
Will the old A358 at Henlade still be a through route? Even with traffic calming and reducing the D2 to S2, it will soon become a rat run to the M5 n/bnd when there are huge summer queues at J25, forewarned by Satnav. Not s/bnd as there would be no advantage.
Also, it looks as if heading through Ilminster w/bnd will still be my route, as it is now.
How can Henlade become a rat run? The only access to the village will be either via the new road or from the roundabout if coming from the M5 so no gain in terms of avoiding J25. Might bypass a queue approaching the roundabout from the A358 but you would still have to negotiate the roundabout!
My latest Road Photos https://flic.kr/s/aHsktQHcMB

Herned
Member
Posts: 799
Joined: Thu Jul 20, 2017 09:15

Re: A358 Taunton to Southfields

Post by Herned » Fri Jun 28, 2019 20:39

Richardf wrote:
Fri Jun 28, 2019 19:50
Might bypass a queue approaching the roundabout from the A358 but you would still have to negotiate the roundabout!
Exactly that, potentially bypassing 2.5 miles of queuing traffic. The queues at J27 coming from North Devon regularly get that long, so it's entirely possible

Richardf
Member
Posts: 1612
Joined: Wed Dec 06, 2006 10:19
Location: Dorchester
Contact:

Re: A358 Taunton to Southfields

Post by Richardf » Fri Jun 28, 2019 21:16

Herned wrote:
Fri Jun 28, 2019 20:39
Richardf wrote:
Fri Jun 28, 2019 19:50
Might bypass a queue approaching the roundabout from the A358 but you would still have to negotiate the roundabout!
Exactly that, potentially bypassing 2.5 miles of queuing traffic. The queues at J27 coming from North Devon regularly get that long, so it's entirely possible
The solution then is to remove the through route in Henlade, so there is no short cut to be had. Cutting the old Road at the roundabout end should achieve this. Access to Henlade and nearby villages via the A378 junction only.
My latest Road Photos https://flic.kr/s/aHsktQHcMB

Post Reply