A3 Guildford tunnel - could it happen?

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jackal
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Re: A3 Guildford tunnel - could it happen?

Post by jackal » Tue Jul 27, 2021 08:48

Phil wrote:
Mon Jul 26, 2021 14:24
Micro The Maniac wrote:
Mon Jul 26, 2021 12:08
Getting slightly further away from Guildford, but today work starts at the A31/A331 junction
The next phase of the works will provide the new lane from the A331 passed the roundabout towards the A31 for Guildford bound traffic. The proposals also include new signal crossings and improvements so the cyclists and pedestrians using the Christmas Pie cycle route can easily and safely cross the slip road which are currently difficult to cross.

It involves the construction of a slip lane for vehicles travelling southbound on the A331, wishing to travel eastbound on the A31, removing the need for them to use the roundabout.
So... the solution to the congestion on a roundabout is (a) put traffic lights on it, but (b) build a free-flow slip - but then put traffic lights on it!
https://www.surreycc.gov.uk/roads-and-t ... at-tongham
If the lights on the free flow slip are for predestinarians and cyclists to cross then I can't see that being an issue. We are hardly talking about Oxford Street proportions of foot traffic which (would be needed to justify grade separation)
Exactly. A freeflow filter onto A31 eastbound is a great improvement and it's splitting hairs to complain about the NMU signals.

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Re: A3 Guildford tunnel - could it happen?

Post by Chris5156 » Tue Jul 27, 2021 14:11

Micro The Maniac wrote:
Mon Jul 26, 2021 12:08
So... the solution to the congestion on aroundabout is (a) put traffic lights on it, but (b) build a free-flow slip - but then put traffic lights on it!
https://www.surreycc.gov.uk/roads-and-t ... at-tongham
I used to think it was a terrible shame this junction hadn't been built free-flow, and that it had never been converted, since it always looked like it should be possible to squeeze enough vertical separation in to install a bridge where the roundabout is.

That's impossible now, though, because the roundabout has a fourth exit with a petrol station and services there. So signalisation it will have to be. The free-flow slip is very welcome though - if it enables two lanes from the A331 to the A31 westbound then that's going to make a big difference to throughput.

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Re: A3 Guildford tunnel - could it happen?

Post by Micro The Maniac » Tue Jul 27, 2021 15:43

Chris5156 wrote:
Tue Jul 27, 2021 14:11
That's impossible now, though, because the roundabout has a fourth exit with a petrol station and services there. So signalisation it will have to be. The free-flow slip is very welcome though - if it enables two lanes from the A331 to the A31 westbound then that's going to make a big difference to throughput.
It is indeed ironic, that during the consultation as to what to do with the junction, planning permission was granted for the services - and it was built and opened.

That said, I think it was always planned, as the fourth arm was built when the roundabout was built.

SMT edit to fix quoting issues

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Re: A3 Guildford tunnel - could it happen?

Post by jackal » Tue Jul 27, 2021 19:07

Pretty stupid that this connection between two grade separated dual carriageways features two-thirds of a semi-directional T, including two skewed bridges, but a roundabout instead of the third.

Even with the services I fancy it would be possible to put in a bridge where the roundabout is, which together with the left turn filter would freeflow 3/4 of the movements.

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Re: A3 Guildford tunnel - could it happen?

Post by Truvelo » Tue Jul 27, 2021 19:24

jackal wrote:
Tue Jul 27, 2021 19:07
Pretty stupid that this connection between two grade separated dual carriageways features two-thirds of a semi-directional T, including two skewed bridges, but a roundabout instead of the third.
I haven't done any research into the proposals for this road but it may be possible there were alternative designs for this junction. There are documents at Surrey Archives from the 1980s which may show some interesting junction layouts. Some other roads planned at this time were built with cheaper junctions by the time they opened in the 90s.
How would you like your grade separations, Sir?
Big and complex.

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Re: A3 Guildford tunnel - could it happen?

Post by Stevie D » Tue Jul 27, 2021 20:20

jackal wrote:
Tue Jul 27, 2021 19:07
Pretty stupid that this connection between two grade separated dual carriageways features two-thirds of a semi-directional T, including two skewed bridges, but a roundabout instead of the third.

Even with the services I fancy it would be possible to put in a bridge where the roundabout is, which together with the left turn filter would freeflow 3/4 of the movements.
It isn't just the services, the junction also provides access to the westbound A31 from Tongham and the ambulance station – and while you could plausibly direct traffic from Tongham and other nearby villages to use the next access point, that probably wouldn't be a good idea for the ambulance route, so the junction needs to provide for that route.

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Re: A3 Guildford tunnel - could it happen?

Post by Bryn666 » Tue Jul 27, 2021 21:15

Stevie D wrote:
Tue Jul 27, 2021 20:20
jackal wrote:
Tue Jul 27, 2021 19:07
Pretty stupid that this connection between two grade separated dual carriageways features two-thirds of a semi-directional T, including two skewed bridges, but a roundabout instead of the third.

Even with the services I fancy it would be possible to put in a bridge where the roundabout is, which together with the left turn filter would freeflow 3/4 of the movements.
It isn't just the services, the junction also provides access to the westbound A31 from Tongham and the ambulance station – and while you could plausibly direct traffic from Tongham and other nearby villages to use the next access point, that probably wouldn't be a good idea for the ambulance route, so the junction needs to provide for that route.
It's the classic British inability to connect two roads without using a roundabout though. It should have been quite feasible to have the A331 freeflow onto the A31 with the services roundabout underneath a flyover. As Jackal says this achieves 3/4 freeflow and would probably eradicate any problems here for, well, ever.
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Re: A3 Guildford tunnel - could it happen?

Post by Chris5156 » Tue Jul 27, 2021 22:23

Stevie D wrote:
Tue Jul 27, 2021 20:20
jackal wrote:
Tue Jul 27, 2021 19:07
Pretty stupid that this connection between two grade separated dual carriageways features two-thirds of a semi-directional T, including two skewed bridges, but a roundabout instead of the third.

Even with the services I fancy it would be possible to put in a bridge where the roundabout is, which together with the left turn filter would freeflow 3/4 of the movements.
It isn't just the services, the junction also provides access to the westbound A31 from Tongham and the ambulance station – and while you could plausibly direct traffic from Tongham and other nearby villages to use the next access point, that probably wouldn't be a good idea for the ambulance route, so the junction needs to provide for that route.
To serve that requirement you only need an additional branch of the entry sliproad from Tongham to continue on the south side of the A31 and join the westbound on-slip from the A331.

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Re: A3 Guildford tunnel - could it happen?

Post by booshank » Tue Jul 27, 2021 23:13

Bryn666 wrote:
Tue Jul 27, 2021 21:15
Stevie D wrote:
Tue Jul 27, 2021 20:20
jackal wrote:
Tue Jul 27, 2021 19:07
Pretty stupid that this connection between two grade separated dual carriageways features two-thirds of a semi-directional T, including two skewed bridges, but a roundabout instead of the third.

Even with the services I fancy it would be possible to put in a bridge where the roundabout is, which together with the left turn filter would freeflow 3/4 of the movements.
It isn't just the services, the junction also provides access to the westbound A31 from Tongham and the ambulance station – and while you could plausibly direct traffic from Tongham and other nearby villages to use the next access point, that probably wouldn't be a good idea for the ambulance route, so the junction needs to provide for that route.
It's the classic British inability to connect two roads without using a roundabout though. It should have been quite feasible to have the A331 freeflow onto the A31 with the services roundabout underneath a flyover. As Jackal says this achieves 3/4 freeflow and would probably eradicate any problems here for, well, ever.
Part of the problem is that services are often attached to interchanges here, which isn't so common in other countries. Overuse of roundabouts helps here as it lends itself to plugging more connections into a single point.

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Re: A3 Guildford tunnel - could it happen?

Post by solocle » Wed Jul 28, 2021 12:20

As for Guildford, a cheap solution as a northern bypass would be to extend the A31 to meet the A3 at the other side of Guildford. That would let you maintain the D2 layout through the centre, but take strategic A31-A3 traffic off it.

Such a bypass would only currently have to be S2. A3-A31 movements are both restricted to one lane as it is. But if you built it as S2+1, to allow overtaking, you'd have one carriageway of a future D3 bypass.
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Re: A3 Guildford tunnel - could it happen?

Post by jackal » Wed Jul 28, 2021 12:38

solocle wrote:
Wed Jul 28, 2021 12:20
As for Guildford, a cheap solution as a northern bypass would be to extend the A31 to meet the A3 at the other side of Guildford. That would let you maintain the D2 layout through the centre, but take strategic A31-A3 traffic off it.

Such a bypass would only currently have to be S2. A3-A31 movements are both restricted to one lane as it is. But if you built it as S2+1, to allow overtaking, you'd have one carriageway of a future D3 bypass.
Capture.JPG
It's an interesting idea. Possibly S2 would be sufficient if you had no intermediate junctions. The problem, though, is that it's virtually the full length of an A3 bypass and would be likely to face similar objections, in which case you might as well build the A3 bypass. (As an aside, D2 might be sufficient for an A3 bypass given a lot of traffic is going to/from Guildford.)

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Re: A3 Guildford tunnel - could it happen?

Post by thatapanydude » Wed Jul 28, 2021 13:03

Could traffic lights be used on the A3 mainline and A31 NB slip at Hog's back to regulate traffic at peak time? Like here in Windsor.
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Re: A3 Guildford tunnel - could it happen?

Post by Stevie D » Wed Jul 28, 2021 15:56

thatapanydude wrote:
Wed Jul 28, 2021 13:03
Could traffic lights be used on the A3 mainline and A31 NB slip at Hog's back to regulate traffic at peak time? Like here in Windsor.
While that can help to ensure that traffic from both roads gets a fair crack of the whip, it doesn't create any more capacity and so doesn't solve the fundamental problem that – between the A31 Hogs Back and A25/A322 Dennis Roundabout at least – the road needs to be D3.

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Re: A3 Guildford tunnel - could it happen?

Post by jackal » Thu Jul 29, 2021 14:14

I didn't realise the A3 in Guildford has the highest NO2 levels on the strategic network, well in excess of legal levels. That does rather cast things in a different light and improves the case for a bypass or perhaps tunnel. This may be why HE dropped the widening scheme, similar to the M60 smart motorway being watered down to nothing due to similar concerns.

https://www.guildford-dragon.com/2021/0 ... y-hotspot/

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Re: A3 Guildford tunnel - could it happen?

Post by thatapanydude » Thu Jul 29, 2021 14:42

Would a toll tunnel be an acceptable solution if let's say charged at £2.50 for cars along with reducing the attractiveness of the A3 through route.
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Re: A3 Guildford tunnel - could it happen?

Post by KeithW » Thu Jul 29, 2021 18:18

thatapanydude wrote:
Thu Jul 29, 2021 14:42
Would a toll tunnel be an acceptable solution if let's say charged at £2.50 for cars along with reducing the attractiveness of the A3 through route.
I doubt it, British motorists dont like tolls and making the A3 less attractive would cause congestion. If your tunnel is D2 then you are talking a minimum of two 10 metre dia tunnels which are likely to each cost between 20 and 40 million pounds per km and there is also the problem of adequate ventilation in a built up area not to mention refuges and/or crossovers depending on the length. The current A3 carries an AADF of 80K so realistically you would probably want a larger tunnel which could double that cost and some land acquisition would be needed for ventilation. The ventilation problem does not go away for electric cars. A Lithium ion battery fire is very nasty and produces some real dangerous fumes.

Circular tunnels are not ideal for UK style HGV's as they have to be quite large , if you want an example from the US take a look at the Big Dig in Boston where the fates combined to make everything go wrong and the final cost came in at $8 billion. Then there was the US 99 tunnel in the Tacoma WA area that came in at $3 billion.

As others have said If you want a cost effective solution a D3 Northern outer bypass would be the way to go. Preferably with a minimal number of junctions to minimise the proliferation of the sort of retail and housing development that developed around the A421 south of Bedford and the Cambridge Northern Bypass. When both of these opened they mostly ran through open fields, that didnt last long.

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Re: A3 Guildford tunnel - could it happen?

Post by Micro The Maniac » Fri Jul 30, 2021 09:06

Micro The Maniac wrote:
Mon Jul 26, 2021 12:08
Getting slightly further away from Guildford, but today work starts at the A31/A331 junction
The next phase of the works will provide the new lane from the A331 passed the roundabout towards the A31 for Guildford bound traffic. The proposals also include new signal crossings and improvements so the cyclists and pedestrians using the Christmas Pie cycle route can easily and safely cross the slip road which are currently difficult to cross.

It involves the construction of a slip lane for vehicles travelling southbound on the A331, wishing to travel eastbound on the A31, removing the need for them to use the roundabout.
So... the solution to the congestion on aroundabout is (a) put traffic lights on it, but (b) build a free-flow slip - but then put traffic lights on it!
https://www.surreycc.gov.uk/roads-and-t ... at-tongham
A quick update... I had the misfortune of having to use this junction yesterday (my oppo, driving, knew better)... at 10am, the southbound A331 was stationary beyond the A323 roundabout (over a mile) - there is a lane closure starting under the roundabout, so taking the exit and rejoining saves about 15 minutes (or until a few more cotton on to this)! The queue westbound along the A31 was back to nearly Puttenham (approx 3 miles). It's going to be a long 8 months (the estimated completion).


But hopefully, worth it.

Suggested route, for car/van-driving locals: A323(E) then Westwood Lane, to pick the A31 at Puttenham/B3000 junction... not HGV friendly.

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Re: A3 Guildford tunnel - could it happen?

Post by Micro The Maniac » Fri Jul 30, 2021 09:38

solocle wrote:
Wed Jul 28, 2021 12:20
Such a bypass would only currently have to be S2. A3-A31 movements are both restricted to one lane as it is. But if you built it as S2+1, to allow overtaking, you'd have one carriageway of a future D3 bypass.
Capture.JPG
Good luck with that... you're traipsing through a Special Protection Area (Whitmoor Common SSSI, part of the Thames Basin Heaths SPA) in the north, and the Surrey Hills Area of Outstanding Natural Beauty to the south-west.

Also your link to the A31 requires a significant elevation change, but doesn't tie in to the A3?

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