The A30 in Cornwall

[Richardf]

Just to move slightly away from the future of Chiverton Cross, to its past. Given its significance on the A30, I was wondering about its history. The layout of the junction is interesting too.

Looking at old maps, and surviving traces visible on Google Earth, the original Chiverton Cross junction between the A30. A390 and B3277 was located to the west where the smaller roundabout is now. The A3075 didnt join here but joined the A30 further to the north east at the end of the section where the two roads run paralel now.

I was wondering when the present roundabout and the extension of the A3075 to it were built and why this layout was used. How also does it fit in with the building of the Blackwater bypass, as the newer roundabout was clearly aligned to fit in with it. Finally how does this all fit in with past/abandoned plans to dual east of this point.

The paralell carriageways of the A30 and A3075 do look odd on a map. I am surprised they havent been combined into an extension of the dual cariageway at some point as a kind of cheap improvement to that section of A30.

[Hdeng16]

Actually you're missing a phase I think. The Blackwater road connected to the main roundabout, the St Agnes road ALSO connected directly to the roundabout AND the Newquay road also connected in. The small newer roundabout is newish.

[crowntown100]

Originally, it was a crossroads between the A30 and B3285 (which went from the original A392 to St Agnes). With a bit of shuffling around, the B3285 became the B3277 and the A390 was extended from Truro to Scorrier along the original A392.

As an easy improvement over the road through Chacewater, the B3277 was upgraded between Threemilestone and Chiverton Cross in the 70's, with the roundabout being built to connect (from the North, clockwise) the B3277 to St Agnes, the extended A3075 to Newquay, the A30 towards Bodmin, the new rebuilt and renumbered A390 (which took over the route from Chiverton Cross to Truro), a little connector to the now severed B3277 to meet the services, and the A30 towards Redruth. Each road had its own arm to the roundabout. I expect the A3075 was extended as the original fork junction wouldn't have seen much, if any, improvement after it was upgraded to an A-road.

When the Blackwater Bypass was built in the late 80's/early 90's, it took over the space that was filled by the stub to the services, meaning that there were now 6 major through roads connecting to the roundabout.

In 2008, Cornwall Council made a few changes, including adding the unhooked left turn from the A390 to the Blackwater Bypass, and combining the B3277 and Blackwater arms into one and building a smaller roundabout on the site of the original crossroads.

I think all of this is documented on the Wiki.

[Richardf]

OK thanks. Sounds like it's had a complicated history. I think I have it worked out!

[jackal]

'Highways England conducting safety study of A30 Hayle bypass as petition calls for U-turn barrier'

http://m.cornwalllive.com/a30-hayle-byp ... story.html

[Richardf]

'Highways England conducting safety study of A30 Hayle bypass as petition calls for U-turn barrier'

http://m.cornwalllive.com/a30-hayle-byp ... story.html

Oh why wasn't it dual in the first place? The road as built is wide enough now so wouldn't have needed to be much wider to fit a D2 in. It's probably the bridges that weren't built wide enough to allow widening now.

[Berk]

It's because it was built in the mid-80s by a government with a very similar outlook to today's one. It was lucky to be built at all.

So as a result, it's a very 'value' project. Lucky that it's even 2+1, rather thuan S2

[Richardf]

Hard to see how it can be made much safer, let alone put a barrier in then?

I suppose alternating the middle lane like at Ilminster wouldn't really help much in this situation? Or is it like that already?

[Berk]

Hard to see how it can be made much safer, let alone put a barrier in then?

I suppose alternating the middle lane like at Ilminster wouldn't really help much in this situation? Or is it like that already?

No, it's just 2 lanes eastbound, one west. And a hard white line between them.

[multiraider2]

Hard to see how it can be made much safer, let alone put a barrier in then?

I suppose alternating the middle lane like at Ilminster wouldn't really help much in this situation? Or is it like that already?

No, it's just 2 lanes eastbound, one west. And a hard white line between them.

Not quite that.

It's got a lane each way at the Hayle End
Then gets a second lane westbound
There's a small bit of s4
Then two lanes eastbound, one westbound
Then back down to s2

So not that dissimilar to Ilminster and just as woefully inadequate in the holiday season.

[Richardf]

The S4 bit could have an Irish style barrier fitted, but even if you lost the hard strips you couldn't do it for the rest of it like that.

Looking at both Hayle and the similarly designed Connor Downs section, I just wonder what they were thinking when they designed an built these roads. Jumping from WS2 to S2+1 to S4 and back again doesn't make much sense. It looks like they just couldn't decide what was best. No wonder drivers get frustrated and impatient on it!

If they were determined to not dual it then a consistent WS2 or S2+1 like Ilminster would have been better. The S4 bits just look dangerous to me.

[wrinkly]

Isn't the bit of S4 just a side effect of the overlap of two climbing lanes?

[A320Driver]

It's possible, just very expensive and disruptive. An example would be Tollbar End, seemingly quite straightforward with just 1 mile of widening and a basic GSJ, but priced over £100m due to the retaining structures and complex traffic management. That would be about half the cost of the entire A30 scheme - not sensible at all when you can build the junction up the road for a fraction of the price.

I've just got back from a week in St Agnes. New section at Temple v.good, no delays.

Having used Chiverton X several times in the week, I got an opportunity to imagine how a GSJ in the present location would look, and I'll be honest I really don't see the issue (apart from cost). Sure, the Starbucks and perhaps the nearest filling station (why why why are there TWO???) would have to go, but the church to the north looks far enough away to not be disturbed. Plenty of land available to the south.

[Richardf]

Isn't the bit of S4 just a side effect of the overlap of two climbing lanes?

No if you look in Google Earth the 4 lane sections are of significant length not just an overlap.

[crowntown100]

The S4 bit could have an Irish style barrier fitted, but even if you lost the hard strips you couldn't do it for the rest of it like that.

Looking at both Hayle and the similarly designed Connor Downs section, I just wonder what they were thinking when they designed an built these roads. Jumping from WS2 to S2+1 to S4 and back again doesn't make much sense. It looks like they just couldn't decide what was best. No wonder drivers get frustrated and impatient on it!

If they were determined to not dual it then a consistent WS2 or S2+1 like Ilminster would have been better. The S4 bits just look dangerous to me.

Hayle & Connor Downs are similarly designed as they were both part of the same contract (Polstrong - St Erth Improvement). The reason the lanes switch is because they are climbing lanes. The WS2 section towards St Erth is like that as it is flat as it goes over the viaduct.

Isn't the bit of S4 just a side effect of the overlap of two climbing lanes?

No if you look in Google Earth the 4 lane sections are of significant length not just an overlap.

400 yards isn't that significant. It's there to try and prevent cars having a head on collision because they've overshot the overtaking lane as it moves the overtaking vehicles on both sides away from each other before they merge back into the single lane.

[Stevie D]

Isn't the bit of S4 just a side effect of the overlap of two climbing lanes?

Pretty much, yes. The overtaking lanes are not just plonked down randomly – the summit is about 45–50m higher than the foot on either side, so it is a significant gradient – there is an overtaking lane on the uphill side in both directions, and they overlap at the top to allow slow traffic to get back up to speed before the lanes merge back.

[BF2142]

'Highways England conducting safety study of A30 Hayle bypass as petition calls for U-turn barrier'

http://m.cornwalllive.com/a30-hayle-byp ... story.html

Oh why wasn't it dual in the first place? The road as built is wide enough now so wouldn't have needed to be much wider to fit a D2 in. It's probably the bridges that weren't built wide enough to allow widening now.

The only impediment to widening on the Hayle bypass is the old railway viaduct - I'm not sure you could get two lanes through each arch? But the odd thing is that the "new build" bridges on the Hayle-Camborne section were intentionally built to only accommodate three lanes, scuppering any easy widening project. That said, there are only a few bridges on that section and it is entirely rural so maybe not such a great cost to widen it online in the future?

[crowntown100]

'Highways England conducting safety study of A30 Hayle bypass as petition calls for U-turn barrier'

http://m.cornwalllive.com/a30-hayle-byp ... story.html

Oh why wasn't it dual in the first place? The road as built is wide enough now so wouldn't have needed to be much wider to fit a D2 in. It's probably the bridges that weren't built wide enough to allow widening now.

The only impediment to widening on the Hayle bypass is the old railway viaduct - I'm not sure you could get two lanes through each arch? But the odd thing is that the "new build" bridges on the Hayle-Camborne section were intentionally built to only accommodate three lanes, scuppering any easy widening project. That said, there are only a few bridges on that section and it is entirely rural so maybe not such a great cost to widen it online in the future?

Not that I've seen them, but I think the original seventies plans did have the dual carriagway splitting, putting a carriage under adjacent arches. However, the eighties happened the a dual carriageway didn't.

Apart from Connor Downs, and the development south of Loggans Moor, it should possible to widen it without too much expenditure in land purchasing. Still can't see it happening though. If they manage to get St Erth to Long Rock in the program, it won't happen before that is done. Otherwise, I can see it staying the same for years as there's no incentive to dual it as it slows traffic into what will be the last section of A30 from Exeter to Long Rock that hasn't been dualled or bypassed.

[multiraider2]

Back from a week in Cornwall. It seemed that whenever I had Pirate Radio on in the car, it was reporting significant delays on the Carland Cross to Chiverton Cross section. I didn't use it once in the holiday. I had arrranged to meet my sister and her family at Trebarwith Strand on the way home, so I used the A3075, A392 and A39 to get there.

Further down and I was contemplating doing this on the way back home, but at 9.15 am last Friday there was only minor slowness between the Newtown Roundabout and the St. Erth Roundabout and no delays at all on the Hayle bypass, so I stuck to the main route.

[RichardEvans67]

I have a few thoughts reguarding the Hayle bypass.

Firstly I'm thinking surely the problem of U-Turns is caused by very slow traffic, and is that largely caused by the next section from St. Erth to Penzance. So I wonder if that section was improved, would that remove the temptation to U-Turn.

I'm also wondering, are traffic levels high enough to justify looking at dueling. I tried a search but couldn't find any figures.

So would it be enough to bypass the villages west of Hyle, or should they eventually be looking at dual all the way to penzance.