Bypass for Thickthorn roundabout, A11/A47

[signol]

The local paper published this article today:
http://www.edp24.co.uk/news/politics/no ... _1_3249001

Interesting idea, I wonder about cost comparison to simply tunneling under the roundabout. I guess it depends how much traffic is through traffic on the A11 only.

signol

[MiChaos]

Thickthorn is an awful roundabout, I don't think I can recall a roundabout with more lights at each arm and with a more appalling road surface! I like the plan in principle, but I do think it needs to join the Norwich-side A11 as a free-flow, not just patch it into the roundabout at the other side! You might be able to get away with it at Hardwick in Lynn, but this is a much, much busier junction!

[Benny]

I've always found it odd that the A11 gets the roundabout whilst the A47 gets the GSJ, surely it should be the other way around?

The obvious answer is a 'Toyota Island'.

[tidalflow]

Thickthorn is an awful roundabout, I don't think I can recall a roundabout with more lights at each arm and with a more appalling road surface! I like the plan in principle, but I do think it needs to join the Norwich-side A11 as a free-flow, not just patch it into the roundabout at the other side! You might be able to get away with it at Hardwick in Lynn, but this is a much, much busier junction!

Spot on about the road surface!

[c2R]

I can't help but think the money would be better spent dualling the Acle Straight, or improving access to King's Lynn (A10 bypass of the villages between Hardwick Roundabout and the A134 turn, for instance). I know there's some queues there, but surely a tunnel here will just increase pressure on the A11 into the city?

[Haydn1971]

Interesting idea, I wonder about cost comparison to simply tunneling under the roundabout. I guess it depends how much traffic is through traffic on the A11 only.

Simply ? I'd suggest that it would be technically challenging in terms of access to the site, complications with disturbing existing structures and much more costly. The solution proposed splits the busy turn movements and is similar to what has been demonstrated to work at M40 J15 - as to if it's a long term solution or just another Catthorpe is debatable though

[Norfolktolancashire]

Why wasn't this the same style junction as the A38/A50 junction west of Derby? The A11 into Norwich itself always was busy without the addition of the bypass traffic from the A47. I also agree with the previous comment that the money would be better spent on bypasses along the A47 east of Kings Lynn.

[Derek]

What I don't get about this is why the off slip from the A11 goes under the road, then climbs over the top of the A47, which is on an embankment, that would be one hell of a climb up. Better, surely, for the off slip to cross over the A11, then it's already half way towards being able to cross the A47.

The Roundhoouse roundabout would be a problem though, with Norwich bound A11 traffic crossing outbound A47 traffic. Given the height it has to climb it's also going to be a lengthy diversion and it'll probably be quicker to go around the roundabout.

Derek

[norwichuk]

Thickthorn is Norfolk's Copdock. I wonder how the HA will find money for this when Copdock is arguably more of a mess and more strategic.

[owen b]

Thickthorn is Norfolk's Copdock. I wonder how the HA will find money for this when Copdock is arguably more of a mess and more strategic.

Wouldn't this be a local scheme rather than an HA scheme? The HA network surely is only the A47 and the A11 as far as the A47.

[norwichuk]

seems like the HA's problem.

“Norfolk County Council, working with us, will be pushing the Highways Agency to fund necessary improvements as a matter of urgency.”

The Highways Agency, which has responsibility for maintaining the roundabout, confirmed it was talking to the county council about a long-term solution.

[Derek]

Thickthorn is Norfolk's Copdock. I wonder how the HA will find money for this when Copdock is arguably more of a mess and more strategic.

Copdock is being improved already isn't it? clicky

Derek

[c2R]

I think if I were the highways agency, I'd tell the council where they could stick it. The problem is clearly caused by the council allowing a tonne of housing development next to the junction, and the council should have appreciated potential traffic flows as part of the planning agreement for the site, and incorporated s106 provision as appropriate for new infrastructure into the schemes.

The HA should therefore suggest closure of local accesses onto the roundabout, and suggest that the city council get funding for a bridge/underpass to carry the B1172 across the A47 and link to the new development on roundhouse way. Accesses to the serviecs would be maintained from the roundabout, but not through access to the B1172.

Similarly close Old Newmarket Road, and link that in with roundhouse way.

Finally close Cantley Lane south.

If the HA then wanted to spend some money, some free flow slips between the A11 and A14 (dir: Lowestoft) just to the north of the railway line south of the junction would be nice.

[M5Lenzar]

Thickthorn is Norfolk's Copdock. I wonder how the HA will find money for this when Copdock is arguably more of a mess and more strategic.

Copdock is being improved already isn't it? clicky

Derek

Those works were certainly not an improvement. Copdock is much worse for the recent meddling that was done there - to the point that I now cut through the villages and use the abandoned D2 to get to the A12.

Copdock should never have been built in its current form. Two major D2s should not use a 2-level junction.

[MiChaos]

I can't help but think the money would be better spent dualling the Acle Straight, or improving access to King's Lynn (A10 bypass of the villages between Hardwick Roundabout and the A134 turn, for instance). I know there's some queues there, but surely a tunnel here will just increase pressure on the A11 into the city?

I could be wrong, but isn't the issue with the Acle Straight environmental rather than financial, with rare blue-beaked dragon-lizards* living by the current alignment?

I have to admit if I'm going to Lynn I avoid the A10 and come across the A47 instead - again though the stretch between the A47 / A17 and the Walpole bypass could certainly do with dualling, as could the Wisbech bypass, both better candidates than the A10 IMO.

What I don't get about this is why the off slip from the A11 goes under the road, then climbs over the top of the A47, which is on an embankment, that would be one hell of a climb up. Better, surely, for the off slip to cross over the A11, then it's already half way towards being able to cross the A47.

The Roundhoouse roundabout would be a problem though, with Norwich bound A11 traffic crossing outbound A47 traffic. Given the height it has to climb it's also going to be a lengthy diversion and it'll probably be quicker to go around the roundabout.

Derek

Completely agree with this. Unless it free-flows onto the Norwich-side A11 there'll be no real benefits for Norwich-bound traffic to use this, no matter how impressive it is.


*Or some such like

[skiddaw05]

The problem is clearly caused by the council allowing a tonne of housing development next to the junction, and the council should have appreciated potential traffic flows as part of the planning agreement for the site, and incorporated s106 provision as appropriate for new infrastructure into the schemes.

I assume the deveoplment you are referring to is the Roundhouse Way one which doesn't have a direct sccess to Thickthorn, and congestion has been an issue here long before the houses were built.

The problem is that is that Thickthorn is the only junction in Norfolk where 3 trunk routes (A47W, A47E ands A11) all meet and should be solved by a freeflow A11N-A47E and A47W-A11S arrangement, rather than what's being proposed as this would mean through traffic still has to go round the roundabout. But even this would be a vast improvement on what is there now, and would be money far better spent than on what is planned up the road at Postwick

[MiChaos]

Also worth noting is that the DfT is looking at ways of improving the A47 and A12: Clicky!

[bart]

I don't know this junction but would assume there are significant traffic movements from the A11 NB to A47 EB and vice-versa, that could be catered for easily with slip roads added to the proposed solution.

[Derek]

I think if I were the highways agency, I'd tell the council where they could stick it. The problem is clearly caused by the council allowing a tonne of housing development next to the junction, and the council should have appreciated potential traffic flows as part of the planning agreement for the site, and incorporated s106 provision as appropriate for new infrastructure into the schemes.

Well, this is a classic example of making plans up as you go along, but it's not actually the fault of Norfolk CC, the HA caused it. Way back when the road was being planned in the early 90's plans were also hatched for the new hospital, built slightly further north near the B1108, which has a junction with the A47. A large part of the reasoning for putting the hospital there was the fact that it was close to the bypass. However, when it got built, the HA refused to allow a junction for the hospital because it was too close to the B1108 junction and, for some reason, it wasn't possible to run a LAR from that junction. So for the first few years of the new hospital's life, access was via the B1108, essentially a country lane; something had to be done. The result was a planning deal and the Roundhouse roundabout was built to allow a feeder road which would also provide the spine for the new Roundhouse housing development.

The HA should therefore suggest closure of local accesses onto the roundabout, and suggest that the city council get funding for a bridge/underpass to carry the B1172 across the A47 and link to the new development on roundhouse way. Accesses to the serviecs would be maintained from the roundabout, but not through access to the B1172.

A good idea but I suspect if you leave the services there moving the traffic from the B1172 (old A11) isn't going to make that much difference. There is also the Park and ride associated with the services and together these make a significant problem on the junction, really having them there is just plain daft. Even if this scheme happened the buses from the P&R would still be using the roundabout.

Similarly close Old Newmarket Road, and link that in with roundhouse way.

Old Newmarket Road is pretty harmless and produces virtually no traffic, but it is used by the fire service for car rescue training (here is a video I made earlier, wear headphones!) so the access is needed.

Finally close Cantley Lane south.

Again, Cantley Lane South is only an off slip, so pretty harmless

If the HA then wanted to spend some money, some free flow slips between the A11 and A14 (dir: Lowestoft) just to the north of the railway line south of the junction would be nice.

Don't follow you there.

The big problems at Thickthorn are the services/P&R, together with the amount of through traffic on the A11. As I say, short term development with no long term vision.

Derek

[signol]

Interesting idea, I wonder about cost comparison to simply tunneling under the roundabout. I guess it depends how much traffic is through traffic on the A11 only.

Simply ? I'd suggest that it would be technically challenging in terms of access to the site, complications with disturbing existing structures and much more costly. The solution proposed splits the busy turn movements and is similar to what has been demonstrated to work at M40 J15 - as to if it's a long term solution or just another Catthorpe is debatable though

In terms of land take, digging under would be simple! But I take your point, the engineering wouldn't be quite so simple!

But even this would be a vast improvement on what is there now, and would be money far better spent than on what is planned up the road at Postwick

Indeed ridiculous. My commute brings me from the bypass over the river, off at Postwick to one of the business parks there. This would mean an additional mile / mile and a half, countless extra roundabouts and business traffic. Not to mention 2 years of disruption while they build it

signol