A358 Taunton to Southfields

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jackal
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Re: A358 Taunton to Southfields

Post by jackal »

Consultation open. The good news - they're getting rid of the Nexus 25 roundabout! The bad news - they're replacing it with a signalised crossroads :roll:

https://highwaysengland.citizenspace.co ... sultation/
Herned
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Re: A358 Taunton to Southfields

Post by Herned »

jackal wrote: Tue May 24, 2022 12:28 Consultation open. The good news - they're getting rid of the Nexus 25 roundabout! The bad news - they're replacing it with a signalised crossroads :roll:

https://highwaysengland.citizenspace.co ... sultation/
I will definitely be putting your idea for a bridge there instead in the consultation. That would make much more sense, then the old A358 can be used for the local traffic. The change to the local road network on the west side at the A378 junction is weird too, the "busiest" connection is to Ash Road, yet they have removed the direct link to the junction.

The consultation has a link to a map of expected traffic changes, they only expect a very small drop in traffic on the A303 west of Ilminster which is slightly surprising
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jackal
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Re: A358 Taunton to Southfields

Post by jackal »

I guess it's a positive that they're recognizing the roundabout should be replaced, they just need to take a step further.

Here's the bridge idea again for the new readers:

M5 J25 - Copy.jpg

East-facing slips could also be considered.
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A303Chris
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Re: A358 Taunton to Southfields

Post by A303Chris »

Herned wrote: Tue May 24, 2022 13:09 The consultation has a link to a map of expected traffic changes, they only expect a very small drop in traffic on the A303 west of Ilminster which is slightly surprising
That is not that surprising as most traffic is travelling Taunton to Yeovil, the flows west of Southfields are quite low, although DFT data has shown an increase up to 2019, but still only around 15,000 to 16,000 AADT.

The flows at the eastern end of the Ilminster bypass are circa 35,000, dropping again east of the A3088.

The A358 carries higher flows than the A303 west of Southfields.

What this all shows is that the busiest area is the the actual Ilminster bypass and with the A358 improved removing the throttle of the existing road, congestion and delays on the bypass will get worse. This needs to be dualled and a free flow provided from the A358 to A303 East.

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Re: A358 Taunton to Southfields

Post by JammyDodge »

jackal wrote: Tue May 24, 2022 13:42 I guess it's a positive that they're recognizing the roundabout should be replaced, they just need to take a step further.

Here's the bridge idea again for the new readers:


M5 J25 - Copy.jpg


East-facing slips could also be considered.
The only slip you would need to consider is this one, to remove traffic going all the way around the roundabout to access the old A358/Nexus25
M5 J25 - Edited.jpg
M5 J25 - Edited.jpg (31.94 KiB) Viewed 747 times
Having an onlip would arguably be unnecessary, due to it being the 1st exit from the roundabout?
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jackal
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Re: A358 Taunton to Southfields

Post by jackal »

You are right, the case for the offslip is clearest. But the onslip might also be a good idea to stop Nexus 25 and P&R traffic going along the old A358 in preference to backtracking to J25. The same could perhaps be achieved with traffic calming on the old A358 or even prohibiting the right turn onto the old A358 here.
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Re: A358 Taunton to Southfields

Post by ikcdab »

jackal wrote: Tue May 24, 2022 12:28 Consultation open. The good news - they're getting rid of the Nexus 25 roundabout! The bad news - they're replacing it with a signalised crossroads :roll:

https://highwaysengland.citizenspace.co ... sultation/
Oh how horrible is the word "signalised" is used by the highway authority....why doesnt the word "signalled" do?
And the roundabout only cost £19.2M. ...so after 18 months maybe time is right to announce its demise...
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Re: A358 Taunton to Southfields

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I was of the understanding that the A358 here was also forming the de facto dual carriageway high-quality link between the A303 and the M5, replacing the substandard section of A303/A30 southwest of Yeovil? That was why I was so baffled by the fact all the strategic traffic was forced through the roundabout serving a local development. Am I mistaken?
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Re: A358 Taunton to Southfields

Post by Peter Freeman »

ikcdab wrote: Tue May 24, 2022 18:57 Oh how horrible is the word "signalised" is used by the highway authority....why doesnt the word "signalled" do?
Because 'signalled' means something different: it's the past tense of the verb 'to signal'.

The adjective 'signalised' comes from the verb 'to signalise', which is formed in the standard way to mean 'conversion to, or addition of, signals'. It's the correct word and the correct usage.

I'm aware that we don't generally indulge in grammatical pedantry on Sabre, but this is an important word in our context, and it's worthwhile to get it right. The validity of the word has been discussed by us previously.
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Re: A358 Taunton to Southfields

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DB617 wrote: Tue May 24, 2022 23:31 I was of the understanding that the A358 here was also forming the de facto dual carriageway high-quality link between the A303 and the M5, replacing the substandard section of A303/A30 southwest of Yeovil? That was why I was so baffled by the fact all the strategic traffic was forced through the roundabout serving a local development. Am I mistaken?
Exactly, it's unbelievably stupid. Building quite large grade separated junctions to access the bright lights of Ashill, while putting in a roundabout/traffic lights to access a thus-far entirely fictional business park is madness.

I have filled in the consultation and made that point, and suggested they build a bridge instead of 9 lanes of traffic lights
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Re: A358 Taunton to Southfields

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Herned wrote: Wed May 25, 2022 09:24
DB617 wrote: Tue May 24, 2022 23:31 I was of the understanding that the A358 here was also forming the de facto dual carriageway high-quality link between the A303 and the M5, replacing the substandard section of A303/A30 southwest of Yeovil? That was why I was so baffled by the fact all the strategic traffic was forced through the roundabout serving a local development. Am I mistaken?
Exactly, it's unbelievably stupid. Building quite large grade separated junctions to access the bright lights of Ashill, while putting in a roundabout/traffic lights to access a thus-far entirely fictional business park is madness.

I have filled in the consultation and made that point, and suggested they build a bridge instead of 9 lanes of traffic lights
Well they ruined the free flow M5 J29 which has got progressively worse with each so called improvement and addition of more signals
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Re: A358 Taunton to Southfields

Post by Phil »

DB617 wrote: Tue May 24, 2022 23:31 I was of the understanding that the A358 here was also forming the de facto dual carriageway high-quality link between the A303 and the M5, replacing the substandard section of A303/A30 southwest of Yeovil? That was why I was so baffled by the fact all the strategic traffic was forced through the roundabout serving a local development. Am I mistaken?
No you are not. The intention is most definitely to upgrade the A358 and use that as an alternative to trying to take on the environmental lobby in forcing a new road through the Blackdown Hills.

But you also need to remember the Government is fixated on Development = automatically good ideology which trumps everything else. So...

the Government fails to object to the Nexus25 plans in the first place (which is simply dumping more private car focused development on the strategic road network)
fails to safeguard any route through the development that would allow a free flow connection to the M5 (can't have the Government reducing any of that 'development land' now can we)
falls over backward to help the developers access needs just so the DfT don't have to pay for 500yards of road.

It stinks - but when the political class are (1) in the pocket of developers and (2) want to do everything on the cheap so they can bleat on about low taxes then what else do you expect?
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Re: A358 Taunton to Southfields

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A303Chris wrote: Wed May 25, 2022 13:45
Herned wrote: Wed May 25, 2022 09:24
DB617 wrote: Tue May 24, 2022 23:31 I was of the understanding that the A358 here was also forming the de facto dual carriageway high-quality link between the A303 and the M5, replacing the substandard section of A303/A30 southwest of Yeovil? That was why I was so baffled by the fact all the strategic traffic was forced through the roundabout serving a local development. Am I mistaken?
Exactly, it's unbelievably stupid. Building quite large grade separated junctions to access the bright lights of Ashill, while putting in a roundabout/traffic lights to access a thus-far entirely fictional business park is madness.

I have filled in the consultation and made that point, and suggested they build a bridge instead of 9 lanes of traffic lights
Well they ruined the free flow M5 J29 which has got progressively worse with each so called improvement and addition of more signals
What a ridiculous junction. The fact that Exeter -> M5 South traffic has to make that ridiculous u-turn is just beyond belief.

I also despise the A379/A3015 GSJ. In its original form, it may have made sense, but when I reached the end of what has to be one of the most expansive non-primary junctions I've ever traversed, I was absolutely amazed to hit two complex signalised junctions.
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Re: A358 Taunton to Southfields

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My hopes aren't much more than floor-high, but I've filled in the consultation all the same.
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Re: A358 Taunton to Southfields

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DB617 wrote: Wed May 25, 2022 17:42 I also despise the A379/A3015 GSJ. In its original form, it may have made sense, but when I reached the end of what has to be one of the most expansive non-primary junctions I've ever traversed, I was absolutely amazed to hit two complex signalised junctions.
Are you suggesting ripping up the GSJ and replacing it with a flat junction then, at taxpayers' expense, for no benefit?

It still works just fine, so I'd say leave it. The fact that there's signalised junctions on the road between there and the M5 might be a little Sabristically displeasing, but it's perfectly understandable. I've never seen that road congested.

(Heck, I'll make the same argument about M5 J29 - yes, it's a big mess, but it works, and doesn't get congested - the main things I don't like about it in practice are 1) the very faded lane markings when performing the E->S movement and 2) the silly lane arrangement that makes everyone have to move a lane to the left when travelling E on the A30. But this one could at least benefit from some freeflow.)
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Re: A358 Taunton to Southfields

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Keiji wrote: Fri May 27, 2022 06:16 (Heck, I'll make the same argument about M5 J29 - yes, it's a big mess, but it works, and doesn't get congested - the main things I don't like about it in practice are 1) the very faded lane markings when performing the E->S movement and 2) the silly lane arrangement that makes everyone have to move a lane to the left when travelling E on the A30. But this one could at least benefit from some freeflow.)
The point is that it did have freeflow, which was removed for no sensible reason whatever. Even if it is never 'congested' it is still operating worse than it would do with the freeflow there, because the 'uncongested' traffic is waiting in the blessed stacking space when it should just be driving to its destination without stopping, like it used to be able to. (This mostly applies to A30wb to M5sb, which was previously freeflow, but in a more qualified form for M5nb to A30eb, which used to have one set of lights to traverse and now has three.)

Many of the failures of junction design in this country are down to the concept that 'no congestion' and 'within capacity' can be achieved by making traffic wait for arbitrarily long periods, provided they have a nice wide bit of road to wait in. By this logic a sufficiently large car park is a higher capacity junction than a four-level stack. See the wonderful results of this in the new designs for M6 J10, M6 J11, Wisley, A358/Nexus 25, and many others. In more enlightened jurisdictions (and occasionally when there is an outbreak of commonsense in the UK) congestion is defined as any departure from freeflowing conditions, i.e., any reduction below 50mph, or whatever the target speed is. By this improved definition any signalized junction is inherently congested. That's not of course to say that they should never be built - far from it - but just that delays should actually be recognized as such and included in the modelling, rather than swept under the carpet.
Last edited by jackal on Fri May 27, 2022 10:37, edited 1 time in total.
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Re: A358 Taunton to Southfields

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Keiji wrote: Fri May 27, 2022 06:16
DB617 wrote: Wed May 25, 2022 17:42 I also despise the A379/A3015 GSJ. In its original form, it may have made sense, but when I reached the end of what has to be one of the most expansive non-primary junctions I've ever traversed, I was absolutely amazed to hit two complex signalised junctions.
Are you suggesting ripping up the GSJ and replacing it with a flat junction then, at taxpayers' expense, for no benefit?

It still works just fine, so I'd say leave it. The fact that there's signalised junctions on the road between there and the M5 might be a little Sabristically displeasing, but it's perfectly understandable. I've never seen that road congested.

(Heck, I'll make the same argument about M5 J29 - yes, it's a big mess, but it works, and doesn't get congested - the main things I don't like about it in practice are 1) the very faded lane markings when performing the E->S movement and 2) the silly lane arrangement that makes everyone have to move a lane to the left when travelling E on the A30. But this one could at least benefit from some freeflow.)
Well, I subsequently did my reading and discovered that it was originally part of the Exeter bypass, hence the huge size and more recent reduction from free flowing to end-signalled. If it had been built with end signals it really would have been a dreadful waste of money, but no, I cannot say I would like to see old GSJs removed and signalised.
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Re: A358 Taunton to Southfields

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jackal wrote: Fri May 27, 2022 10:13Many of the failures of junction design in this country are down to the concept that 'no congestion' and 'within capacity' can be achieved by making traffic wait for arbitrarily long periods, provided they have a nice wide bit of road to wait in. By this logic a sufficiently large car park is a higher capacity junction than a four-level stack. See the wonderful results of this in the new designs for M6 J10, M6 J11, Wisley, A358/Nexus 25, and many others. In more enlightened jurisdictions (and occasionally when there is an outbreak of commonsense in the UK) congestion is defined as any departure from freeflowing conditions, i.e., any reduction below 50mph, or whatever the target speed is. By this improved definition any signalized junction is inherently congested. That's not of course to say that they should never be built - far from it - but just that delays should actually be recognized as such and included in the modelling, rather than swept under the carpet.
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Re: A358 Taunton to Southfields

Post by SteveA30 »

Yes, a bridge with east facing slips for Nexus. Developers really are in charge these days, same with new housing sprawling out of most towns nowadays, messing up bypasses.
Here is M5 J29 as it was from 1975 to... 2010? The original S2 becoming D2 under the M5 and freeflow for all. Even when the D2 was opened in Aug 99, it was freeflow for a while. Note the fields beyond the M5, now all built on, with many more signalled junctions along the way.
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Re: A358 Taunton to Southfields

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SteveA30 wrote: Fri May 27, 2022 11:00 Yes, a bridge with east facing slips for Nexus. Developers really are in charge these days, same with new housing sprawling out of most towns nowadays, messing up bypasses.
Here is M5 J29 as it was from 1975 to... 2010? The original S2 becoming D2 under the M5 and freeflow for all. Even when the D2 was opened in Aug 99, it was freeflow for a while. Note the fields beyond the M5, now all built on, with many more signalled junctions along the way.
I would not say developers, they are tied by the rules local planning authorities and highway authorities make. They are so desperate to make there housing allocations and pushing active travel they fall for viability issues every time. Often a developer will have priced for a better junction, but pull the viability argument and can get the proposals watered down.

All goes down to the lack of experience within the local authorities and the lack of professionally qualified staff.
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