A487 Caernarfon Bypass

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AAndy
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A487 Caernarfon Bypass

Post by AAndy » Wed Dec 02, 2020 08:29

The construction looks to be on schedule, and quite surprising the scale of the works.

Once constructed the largely fast flowing A487 make a good North / South alternative to the A470 connection with the A55 from here https://www.google.co.uk/maps/@52.93719 ... 384!8i8192

https://gov.wales/a487-caernarfon-bontn ... s-overview

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Re: A487 Caernarfon Bypass

Post by A303Chris » Wed Dec 02, 2020 13:46

AAndy wrote:
Wed Dec 02, 2020 08:29
The construction looks to be on schedule, and quite surprising the scale of the works.

Once constructed the largely fast flowing A487 make a good North / South alternative to the A470 connection with the A55 from here https://www.google.co.uk/maps/@52.93719 ... 384!8i8192

https://gov.wales/a487-caernarfon-bontn ... s-overview
Conway from that junction is 33 miles and via Carnarvon is 51 miles. I think time wise even for the last 17 miles being on the A55, there would not be much in it travelling wise.

Although I have to say the design with long stretches of overtaking lanes is great for the volume of traffic, and it is something Transport Wales does well. In England, we still build 7.3 metre wide SC bypasses which take the traffic out of a village , but you can not overtake a slow vehicle due to the volume of traffic. Take the A327 Arborfield Relief Road opened last month in Berkshire and I did a post last week , just SC throughout
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Re: A487 Caernarfon Bypass

Post by DB617 » Wed Dec 02, 2020 16:30

A303Chris wrote:Transport Wales
Tf*W don't currently handle trunk roads (though I wish they did as it would bring it all under one roof); only public transport strategy and rail. I assume this falls under the handily named NWTRA. Wales doesn't have the current English Government's interest in catchy ministry titles, as you can tell.

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Re: A487 Caernarfon Bypass

Post by jackal » Wed Dec 02, 2020 20:51

A303Chris wrote:
Wed Dec 02, 2020 13:46
AAndy wrote:
Wed Dec 02, 2020 08:29
The construction looks to be on schedule, and quite surprising the scale of the works.

Once constructed the largely fast flowing A487 make a good North / South alternative to the A470 connection with the A55 from here https://www.google.co.uk/maps/@52.93719 ... 384!8i8192

https://gov.wales/a487-caernarfon-bontn ... s-overview
Conway from that junction is 33 miles and via Carnarvon is 51 miles. I think time wise even for the last 17 miles being on the A55, there would not be much in it travelling wise.

Although I have to say the design with long stretches of overtaking lanes is great for the volume of traffic, and it is something Transport Wales does well. In England, we still build 7.3 metre wide SC bypasses which take the traffic out of a village , but you can not overtake a slow vehicle due to the volume of traffic. Take the A327 Arborfield Relief Road opened last month in Berkshire and I did a post last week , just SC throughout
There are S2+1 stretches like that in England, and they are generally not well regarded, e.g., the A303 Ilminster Bypass or A30 between Camborne and Hayle. The thing is you're spending three quarters of the cost of a dual carriageway but without the safety benefit of divided carriageways or consistency of capacity - if volumes rise you essentially have a series of one lane bottlenecks. And S2+1 is generally rather difficult to upgrade to DC: the three lane viaduct at Carnavon suggests this tradition will be continued.

I would prefer either that they spend a little more to dual it properly or (if that's off the table) use a mixture of dualling and S2. The job would then be smaller if it is later decided that continuous D2 is required, and on a road with several major junctions like the Carnavon bypass there usually will be significant changes in volume along the way that can be accommodated better by a mixture of S2 and D2 than by blanket S2+1.

S2+1 climbing lane sections are useful, but that's a rather different use case.

All that said, it is quite an impressive bypass.

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Re: A487 Caernarfon Bypass

Post by darkcape » Wed Dec 02, 2020 21:40

The S2+1 format works quite well on the Newton bypass and this seems a similar model. I'd prefer less roundabouts. I suspect the authorities are fairly satisfied they will never upgrade to full D2. The +1 sections provide ample overtaking opportunities.
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Re: A487 Caernarfon Bypass

Post by Herned » Wed Dec 02, 2020 23:35

jackal wrote:
Wed Dec 02, 2020 20:51
There are S2+1 stretches like that in England, and they are generally not well regarded, e.g., the A303 Ilminster Bypass or A30 between Camborne and Hayle.
Entirely dependent on traffic volumes. Most of the time the Ilminster bypass flows well, but it does cause bottlenecks once you get to a certain level. On quieter roads 2+1 is ideal

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Re: A487 Caernarfon Bypass

Post by rhyds » Thu Dec 03, 2020 10:47

AAndy wrote:
Wed Dec 02, 2020 08:29
The construction looks to be on schedule, and quite surprising the scale of the works.

Once constructed the largely fast flowing A487 make a good North / South alternative to the A470 connection with the A55 from here https://www.google.co.uk/maps/@52.93719 ... 384!8i8192

https://gov.wales/a487-caernarfon-bontn ... s-overview
From Gelliydan heading north the A487 bypass at Caernarfon (along with Porthmadog's existing diversion) will make a very big difference as the A470 is of a pretty low standard through Ffestiniog and over the Crimea It then dumps you in to Betws y Coed, which along with Llanrwst doesn't exactly flow well during the average summer.
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Re: A487 Caernarfon Bypass

Post by rhyds » Thu Dec 03, 2020 10:49

A303Chris wrote:
Wed Dec 02, 2020 13:46
AAndy wrote:
Wed Dec 02, 2020 08:29
The construction looks to be on schedule, and quite surprising the scale of the works.

Once constructed the largely fast flowing A487 make a good North / South alternative to the A470 connection with the A55 from here https://www.google.co.uk/maps/@52.93719 ... 384!8i8192

https://gov.wales/a487-caernarfon-bontn ... s-overview
Conway from that junction is 33 miles and via Carnarvon is 51 miles. I think time wise even for the last 17 miles being on the A55, there would not be much in it travelling wise.
One quick point: Conway was a singer and Carnarvon was someone who dug holes in Egypt.

A303Chris wrote:
Wed Dec 02, 2020 13:46
Although I have to say the design with long stretches of overtaking lanes is great for the volume of traffic, and it is something Transport Wales does well. In England, we still build 7.3 metre wide SC bypasses which take the traffic out of a village , but you can not overtake a slow vehicle due to the volume of traffic. Take the A327 Arborfield Relief Road opened last month in Berkshire and I did a post last week , just SC throughout
Welsh trunk road traffic volumes work well for S2+1, as the issue is rarely the volume of traffic, but rather getting stuck behind a long/heavy/agricultural vehicle with no suitable overtaking spots.
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Re: A487 Caernarfon Bypass

Post by Chris5156 » Thu Dec 03, 2020 15:49

rhyds wrote:
Thu Dec 03, 2020 10:49
A303Chris wrote:
Wed Dec 02, 2020 13:46
Conway from that junction is 33 miles and via Carnarvon is 51 miles.
One quick point: Conway was a singer and Carnarvon was someone who dug holes in Egypt.
No, come on Rhyds. Let's be fair. Conway can also mean the man who played brilliant tinkly piano tunes :wink:

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Re: A487 Caernarfon Bypass

Post by Bryn666 » Thu Dec 03, 2020 18:20

What will be interesting to see is if anyone comes up with any sane options for the old A487. The flyover in the town centre will no doubt be attracting "knock it down" crowds.
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Re: A487 Caernarfon Bypass

Post by roadtester » Thu Dec 03, 2020 18:57

Chris5156 wrote:
Thu Dec 03, 2020 15:49
rhyds wrote:
Thu Dec 03, 2020 10:49
A303Chris wrote:
Wed Dec 02, 2020 13:46
Conway from that junction is 33 miles and via Carnarvon is 51 miles.
One quick point: Conway was a singer and Carnarvon was someone who dug holes in Egypt.
No, come on Rhyds. Let's be fair. Conway can also mean the man who played brilliant tinkly piano tunes :wink:
Conway was also Rolls-Royce turbofan engine that saw distinguished service in the VC10 and several other aircraft of the era.

https://en.wikipedia.org/wiki/Rolls-Royce_Conway
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Re: A487 Caernarfon Bypass

Post by Truvelo » Thu Dec 03, 2020 19:01

The sane option for the old A487 is to leave it as it is so traffic within the town can circulate more freely. It will also be needed for when the area within the bypass becomes infilled with tin sheds and dog boxes which will attract its own traffic.
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Re: A487 Caernarfon Bypass

Post by Ruperts Trooper » Thu Dec 03, 2020 19:39

roadtester wrote:
Thu Dec 03, 2020 18:57
Chris5156 wrote:
Thu Dec 03, 2020 15:49
rhyds wrote:
Thu Dec 03, 2020 10:49
One quick point: Conway was a singer and Carnarvon was someone who dug holes in Egypt.
No, come on Rhyds. Let's be fair. Conway can also mean the man who played brilliant tinkly piano tunes :wink:
Conway was also Rolls-Royce turbofan engine that saw distinguished service in the VC10 and several other aircraft of the era.

https://en.wikipedia.org/wiki/Rolls-Royce_Conway
And made trailer tents https://www.conwayowners.org.uk/conwaytrailertents.htm
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Re: A487 Caernarfon Bypass

Post by Bryn666 » Thu Dec 03, 2020 21:16

Truvelo wrote:
Thu Dec 03, 2020 19:01
The sane option for the old A487 is to leave it as it is so traffic within the town can circulate more freely. It will also be needed for when the area within the bypass becomes infilled with tin sheds and dog boxes which will attract its own traffic.
Yes I think it's rather established that such infill is demonstrably insane but people keep advocating it.
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Re: A487 Caernarfon Bypass

Post by Chris Bertram » Thu Dec 03, 2020 22:17

Chris5156 wrote:
Thu Dec 03, 2020 15:49
rhyds wrote:
Thu Dec 03, 2020 10:49
A303Chris wrote:
Wed Dec 02, 2020 13:46
Conway from that junction is 33 miles and via Carnarvon is 51 miles.
One quick point: Conway was a singer and Carnarvon was someone who dug holes in Egypt.
No, come on Rhyds. Let's be fair. Conway can also mean the man who played brilliant tinkly piano tunes :wink:
... and a subsequent Carnarvon was the Queen's racing manager. The current holder of the title owns Downton Abbey, or if you prefer, Totleigh Towers (both portrayed on screen by Highclere Castle).
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AAndy
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Re: A487 Caernarfon Bypass

Post by AAndy » Sat Dec 05, 2020 16:22

A303Chris wrote:
Wed Dec 02, 2020 13:46
AAndy wrote:
Wed Dec 02, 2020 08:29
The construction looks to be on schedule, and quite surprising the scale of the works.

Once constructed the largely fast flowing A487 make a good North / South alternative to the A470 connection with the A55 from here https://www.google.co.uk/maps/@52.93719 ... 384!8i8192

https://gov.wales/a487-caernarfon-bontn ... s-overview
Conway from that junction is 33 miles and via Carnarvon is 51 miles. I think time wise even for the last 17 miles being on the A55, there would not be much in it travelling wise.

Although I have to say the design with long stretches of overtaking lanes is great for the volume of traffic, and it is something Transport Wales does well. In England, we still build 7.3 metre wide SC bypasses which take the traffic out of a village , but you can not overtake a slow vehicle due to the volume of traffic. Take the A327 Arborfield Relief Road opened last month in Berkshire and I did a post last week , just SC throughout
rhyds wrote:
Thu Dec 03, 2020 10:47


From Gelliydan heading north the A487 bypass at Caernarfon (along with Porthmadog's existing diversion) will make a very big difference as the A470 is of a pretty low standard through Ffestiniog and over the Crimea It then dumps you in to Betws y Coed, which along with Llanrwst doesn't exactly flow well during the average summer.
What Rhyds says Chris ^^

Though I will add that I much prefer the 'longer' route even at present.

Here is a short video of some of the construction:
https://youtu.be/IGoV_w_7ygM

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Re: A487 Caernarfon Bypass

Post by nowster » Tue Jan 26, 2021 22:26

Has anyone noticed that the OS has got the route choice wrong?

Look around Bethel to the east of Caernarfon on the OS Modern layer on Sabre Maps (direct linking for that layer doesn't work, unfortunately).

StreetMap shows the same error at the 1:50k level: http://www.streetmap.co.uk/map.srf?X=25 ... &A=Y&Z=120

(Bing OS Mapping has old tiles.)

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Re: A487 Caernarfon Bypass

Post by wrinkly » Tue Jan 26, 2021 22:57

nowster wrote:
Tue Jan 26, 2021 22:26
Has anyone noticed that the OS has got the route choice wrong?
I hadn't notice that. The route they show seems to be he one that was first chosen and then fairly quickly changed - called the purple route IIRC.

Edit: just found this link in a post from the previous thread:

https://www.bbc.co.uk/news/uk-wales-nor ... s-22551939

The choice of the purple route lasted 10 months - odd to see it on a map 8 years later!

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Re: A487 Caernarfon Bypass

Post by wrinkly » Wed Mar 10, 2021 18:33


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Re: A487 Caernarfon Bypass

Post by Peter Freeman » Thu Mar 11, 2021 08:06

jackal wrote:
Wed Dec 02, 2020 20:51
... The thing is you're spending three quarters of the cost of a dual carriageway but without the safety benefit of divided carriageways or consistency of capacity - if volumes rise you essentially have a series of one lane bottlenecks. And S2+1 is generally rather difficult to upgrade to DC: the three lane viaduct at Carnavon suggests this tradition will be continued.

I would prefer either that they spend a little more to dual it properly or (if that's off the table) use a mixture of dualling and S2. The job would then be smaller if it is later decided that continuous D2 is required, ...
(my emphasis above - PF)

I generally approve of alternating S2+1 (and very strongly disapprove of WS2 !). Someone has suggested up-thread that traffic on this rural road in North Wales is unlikely in the foreseeable future to grow significantly, so S2+1 is probably OK. In AU we tend to use this road format too, but here it is less advisable because we have inevitable traffic growth due to a national policy of increasing our population.

Having said that, and despite also liking the look of this project, 'a mixture of dualling and S2' would be exactly my preference too. It allows nicely for subsequent dualling completion. Safety would be improved, especially if the S2 lengths incorporated wide centreline treatment and/or central barriers. Total project price would be lower because the S2 sections could be used at points of highest construction cost - for example, over the viaduct and in the rather deep cutting that exists at one point.

I'd place dual sections before and after each roundabout, and at other needy points such as up-gradients
jackal wrote:
Wed Dec 02, 2020 20:51
... and on a road with several major junctions like the Carnavon bypass there usually will be significant changes in volume along the way that can be accommodated better by a mixture of S2 and D2 than by blanket S2+1.
I agreed with this statement when I first read it. However, on deeper thought, I think the opposite is true. To the first order, this alternative strategy of S2/D2 can provide exactly the same number of overtaking opportunities with an equal area of road surface. However, it is arguable that S2+1 might allow more judicious positioning of its 2-lane sections. This because D2 might put a 2-lane carriageway on the side where it is needed, but wastefully impose 2 lanes on the opposite side even though it is not required there. That wasted area of road surface could be better deployed elsewhere.

Regardless, I favour the S2/D2 mix!

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