A11 Angers Bypass 3 Level roundabout stack

Fluid Dynamics · Post by **Fluid Dynamics** » Fri Apr 04, 2008 22:36

Forgive me if I am wrong, I have spotted this very un-French design for one of the new junctions on the new A11 Angers Bypass. A little to the East there is also a significant amount of cut and cover tunneling.

http://maps.google.com/maps?f=q&hl=en&g ... 1&t=k&z=17

Fluid Dynamics · Post by **Fluid Dynamics** » Fri Apr 04, 2008 22:42

They Must be catching on as this one is also under construction on a new urban Motorway in North East Marseille. Follow the route South and more tunneling.

http://maps.google.com/maps?f=q&hl=en&g ... 1&t=k&z=17

RoadaddictReece · Post by **RoadaddictReece** » Fri Apr 04, 2008 22:44

Take note french government.

That design does not work well in britain.

When will transport departments learn? 3 level stacks are uncool!

Fluid Dynamics · Post by **Fluid Dynamics** » Fri Apr 04, 2008 22:57

Exactly, we have spent large amounts of money on improving/bypassing Ferrybridge and Lofthouse.

I would assume from the design that the A11 around Angers will be free as the French are prone to putting awful double trumpet junctions in on most similar junctions. Will be interesting to see what they do with the existing road through Angers. In the UK we would grass it over or turn it into a park and ride car park.

Bryn666 · Post by **Bryn666** » Fri Apr 04, 2008 23:00

The French can build these junctions as their autoroutes take about a tenth of the traffic our motorways do.

The A11 carries probably about the same amount of traffic as the A55 on Anglesey. The nearby A85 carries a mere 8,500 vpd.

EDIT: The A11 beyond Angers is free - the toll gate is at the A85 junction.

mwacuk · Post by **mwacuk** » Fri Apr 04, 2008 23:10

They seem to have made the roundabout extremely small the first junction considering it is surrounded by fields. The problem is that the entrys and exits are going to be far too close together, unless they are going to be signalised?

marc

Fluid Dynamics · Post by **Fluid Dynamics** » Fri Apr 04, 2008 23:13

From my experience the A11/N23 through Angers is quite busy. I have not driven the section between ANgers and Nantes, but the A85 to Bourgeuil was particularly empty when I used it back in 2002, but this was prior to the Bourgeuil - Langeis section opening (is it open yet).

It has also perplexed me why the A85 was built to the Tours Ring Road and yet is now being diverted south. Was this always part of the plan. I also see on google maps that the Tours Ring Road (not complete) is being extended north of the Loire on its Western side.

Bryn666 · Post by **Bryn666** » Fri Apr 04, 2008 23:32

The A85 is now open all the way to the N585 at Tours I believe.

As for the southern diversion, that was always the plan but the first bit was built as an approach road into Tours to bypass the crummy bits of the N152.

The N23 through Angers is only busy because it's got all the cross-city traffic too. The A11 will take all through traffic meaning the N23 will be purely for commuting.

scragend · Post by **scragend** » Sat Apr 05, 2008 01:33

Interesting to read about this - I'm quite familiar with Angers (Wigan's twin town) and, although I haven't been for about 5 years, I will be there this July. I wasn't aware of this road being built.

It seems to be scheduled to open in August this year so won't yet be open when I'm there; I'll have to go again next year to see the impact it has had

Bryn666 wrote:EDIT: The A11 beyond Angers is free - the toll gate is at the A85 junction.

True, but I think it becomes péage again after Angers heading towards Nantes. Will it become péage all the way when the missing section is completed?

Bryn666 · Post by **Bryn666** » Sat Apr 05, 2008 01:48

Judging by the planned layouts of GSJs, I'd say no.

Stephen from Wuss · Post by **Stephen from Wuss** » Wed Apr 09, 2008 10:22

French motorways in general are not as well engineered as UK motorways. You get long single lane link roads at motorway junctions, even around Paris. which can be frustrating.

I notice Angers is where the A11 and A85 come although from ViaMichelin it would appear they are using the existing ring road as part of the scheme (N23/N260), so the A11 will use the N23 between junctions 14 and 15, and to get to the A85 you would need to use the N260 from junction 14 of the A11.

I note the N260 already has GSJ, and local traffic will use the old N23 from junction 15 that follows the Loire. Hopefully getting around Angers will become much easier with this new motorway.

The toll booths for both the A11 and A85 are some distance from Angers suggesting the new motorway on the photograph will be "free". Often where this happens there are 3 lanes on each carriageway as to to the usual 2, as at nearby Tours on the A10.

sotonsteve · Post by **sotonsteve** » Thu Apr 10, 2008 10:55

Stephen from Wuss wrote:French motorways in general are not as well engineered as UK motorways.

Correction. British motorways from the old days were well engineered affairs, but look at more recent developments and the standards have clearly dropped. The M6Toll has lots of narrow and tight slip roads, and near to me, the M3 through Twyford Down has some very steep slip roads, with the onslips only one lane wide, meaning traffic normally joins the motorway at 40-45mph, and congestion prevails.

Even if French traffic levels are lower, which they generally are, they shouldn't make the same mistakes as us and connect two motorways with a three level stacked roundabout. When the junctions on the M27 were built they were probably adequate for the traffic volumes, but the traffic volumes grew.

You get a bit of three level stacking in the USA, although where I saw it there were lots of freeflows bypassing the signalised bit. Effectively, the ones I saw were signalised squarebouts.

The worst traffic I've experienced in France was on a toll motorway on the approach to the toll booths.

Bryn666 · Post by **Bryn666** » Thu Apr 10, 2008 13:29

Thing is, the French don't build massive Ikeas and housing estates alongside their motorways so the traffic volumes rarely grow beyond the natural rise in traffic. The A85 is just as rural as it was 10 years ago when it first opened, and is still so quiet that the MSA between Bourgeuil and Angers closes at 9pm.

However, I don't understand why no one has bypassed the N147 yet, especially between the A10 and A20, that is a horrid road!

Stephen from Wuss · Post by **Stephen from Wuss** » Thu Apr 10, 2008 13:33

Standards in the UK may have appeared to have slipped, but this is probably due compromises as a result of the finances and the environmental lobby. Sadly we aren't building new motorways at any where near the same rate as the French so I don't think we can compare current engineering standards. I look at recent projects such as the A28 south of Alençon where only one bridge was initially opened across a river (so it was just 1 lane in each direction), or the junction of the A28 with the A11 near Tours with its narrow slip roads, or further east the junction with the A85/A71 north of Vierzon. In the UK we tend to not build slip roads between motorways as narrow. To be fair to the French the three instances I have mentioned do appear to cope with the traffic volumes.

I don’t think French use their hard shoulders as we do when lanes are out for motorway repairs, instead going to single line traffic that can run for a considerable distance. Perhaps someone can clarify if French hard shoulders are up to running strength, or are they like the hard shoulders on earlier UK motorways?

Queuing at tolls can be an issue, especially during public the French holidays. I use a Libert-T badge which means I can use the reserve automated tolls, although if traffic is queuing for miles it will only help when you reach the wide carriageway before the Gare de Peage when you can get into the appropriate lane. I have put a post on the thread relating to a guide to France which explains how to get one.

There have been comments on other threads about the number of motorway slip roads that have been converted to only a single lane in the UK. Many of these are still wide enough to accommodate 2 lanes, but most French slip roads were only designed to have a single lane e.g. around Le Mans. One of my work colleagues is attending the 24-Hour Race so it will be very interesting to hear how well the autoroute copes around the A11-A28 junction.

Bryn666 · Post by **Bryn666** » Thu Apr 10, 2008 13:45

French sliproads are a bit of a bugbear of mine - with all the available land they still insist on a 30km/h exit loop - but perhaps this is to slow you down on the approach to a tollbooth.

Then you realise that non-tolled roads are exactly the same! I think it's all about reducing your speed from 130km/h to something more suited to the ordinary road network. In the UK you fly off the motorway at 70 and have to slam on for the roundabout - neither situation is ideal.

The A28 bridge at Alencon has since been dualled, but there are two large viaducts near Bernay which are still D1. Incidentally, all the A28 mainline tolls have had to be expanded due to massive queues on an otherwise empty road.

French hard shoulders vary - some are gravelly, others are full strength but not full width. You couldn't have running lanes on them, they are too narrow.

As for Liber-T - it needs a dedicated lane from about 1km before the toll plaza then you can genuinely soar past the queue.

sotonsteve · Post by **sotonsteve** » Thu Apr 10, 2008 15:30

All French motorways that I've been on have proper tarmac hard shoulders. In fact, all but one motorway that I went on during my last visit had excellently smooth surfaces. The exception was an old concrete motorway, which just happened to be having extensive roadworks done to it at the time I passed through. I can't remember the running lane on hard shoulder situation for sure, but I think they did put the hard shoulder into use.

Stephen from Wuss · Post by **Stephen from Wuss** » Fri Apr 11, 2008 13:12

The French autoroutes have superb smooth running surfaces, and the only poor road surface I came across was on the A9 between Avignon and Nimes which I guess was one of the earlier motorways.

What is good about the new French motorways is they are improving links from Normandy, which is great for those of us who use the ferry routes into Caen and they are developing a series of east-west routes across France.

Regarding the Libert-T electronic tolling system there should be greater discounts to encourage its useage. If virtually all French motorists were on this scheme the collection of tolls would be much quicker and queues would become much less likely. (I would also guess there would be job losses amongst the toll booth staff)

Bryn666 · Post by **Bryn666** » Fri Apr 11, 2008 13:14

That must be the lonliest job on earth - sat in a tollbooth on a rural exit sliproad with one car every 3 hours

jackal · Post by **jackal** » Sat Apr 12, 2008 18:58

sotonsteve wrote:
Stephen from Wuss wrote:French motorways in general are not as well engineered as UK motorways.
Correction. British motorways from the old days were well engineered affairs, but look at more recent developments and the standards have clearly dropped. The M6Toll has lots of narrow and tight slip roads, and near to me, the M3 through Twyford Down has some very steep slip roads, with the onslips only one lane wide, meaning traffic normally joins the motorway at 40-45mph, and congestion prevails.

Actually I think things are rather more complicated. For one thing Twyford Down is quite an old road now, so it's hard to tell whether it's evidence that things have got worse or better. For another the M6 Toll junctions are deliberately designed with the toll booths in mind - for that reason it is an obvious exception. There are admittedly one or two signs of cost cutting on other fairly recent projects (the eastern side of the M60 has a few) but to tell the story just as one of decline is to forget the stuff we get right now and got wrong before. For example, M60/M62/M66 aside (which was reusing older infrastructure anyway), we seem to have a better idea of how to join two motorways together now than we did before. Look at the recent A1(M)/M62 interchange or either end of the M1 extension (very generously proportioned Y-interchanges merging seamlessly into D4M/D5M). These do what they do with as much scale and style as anything on the network. And then remember that once upon a time it was thought that a stacked roundabout could do the A1/M62 and M1/M62 jobs. So in general I'd say UK motorway engineering standards are about as high as they've ever been, and certainly higher than they are in France (see below).

Even if French traffic levels are lower, which they generally are, they shouldn't make the same mistakes as us and connect two motorways with a three level stacked roundabout. When the junctions on the M27 were built they were probably adequate for the traffic volumes, but the traffic volumes grew.

I think a stacked roundabout interchange will be more than adequate for present and future traffic levels. It doesn't make sense to apply UK motorway standards to french motorways since most of the latter are much quieter. Demanding something better than a stacked roundabout (presumably something like a whirlpool, octopus, or upgraded cloverleaf) is (in traffic volume terms) the equivalent of demanding such an extravagance where a UK HQDC meets an average S2 A road. Extend that across an entire network and you're looking at a phenomenal waste of money. So it makes sense for the French to have lower standards, and go for stacked roundabouts, double trumpets, and so on.

JamesA44 · Post by **JamesA44** » Mon Apr 14, 2008 12:10

I've always been quite impressed by the 3 level stack at M5 J11. (Obviously that's not 2 motorways meeting though)