Why do British Highway Engineers Hate Free-Flow Junctions?

[Bletchleyite]

But do you care that people will endure needless congestion in the future until the next generation decides to stump of thrice as much as what it would have cost to build things to a proper standard in the first place?

I do not experience significant congestion at these junctions.

 

[stuu]

I do not experience significant congestion at these junctions.

Which junctions though? Some are much worse than others, obviously, and they are the ones which are having to be upgraded at eye-watering costs - it's much, much cheaper to do it right the first time than try to work around live motorways

 

[Bletchleyite]

Which junctions though? Some are much worse than others, obviously, and they are the ones which are having to be upgraded at eye-watering costs - it's much, much cheaper to do it right the first time than try to work around live motorways

Some are a problem, sure. But I can't remember the last time I got stuck in significant congestion at a motorway junction roundabout. Roundabouts have advantages, too - they are simple to use, all destinations are accessible including back the way you came, and they are cheap.

 

[The Planner]

Excellent thread choice!

Precisely this - penny-pinching by (usually) the Treasury is a big problem.
Gold-plated standards don't help though. Neither does the issue of consultants deliberately creating future work for themselves, not the seeming lack of appetite by road authorities (local or national) to challenge what their consultants tell them (and housing developers...)

"Upgrade" isn't really the word I'd use. "Complete utter waste of money" is more appropriate


There likely was 20-30 years ago when an overall masterplan for the current mess that is the Kegworth junction complex should have been created

It used to be a trumpet (you can see where the loop used to be on the eastern side of the M5). When the M5 was widened* (due to, surprise surprise, short sightedness of building the bit between Birmingham (J3 maybe?) and J8 as two lanes; south of J8 has always been three) it was changed to a roundabout (Strensham Services were also rebuilt at this time).

*Of course, had the correct decision been made to build a motorway between Strensham and the M42/M40 junction, as nearly happened twice, instead of widening, we'd have ended up with a much more interesting (and free flow) design (I'll post some links later).

Occasionally, National Highways(' consultants) can come up with some kind of free-flow junction. Look at the spaghetti fests that are planned where the lower Thames crossing meets the A13 and M2. Although on that subject, we come to the stupidity that the LTC will be a restricted A road (like the new A14 at Huntington) rather than a motorway).

As for roundabouts, small, simple ones are fine. Enormous, multi-lane signalled ones are an abomination that screams "we don't know how to do anything other than add more lanes and traffic lights and hope for the best".


More posting will follow this evening once I'm back home...

Seeing as the first bit of the M5 opened in 1962, probably taking 18 months to build, design etc another few years before that you are talking mid to late 1950s when car use was still relatively low, pre-empting growth was going to be difficult. It was still 30 years before it was widened. Same goes for the M1, took 30 years for the 2 lane section at the southern end to be widened. Amazing how hindsight is a wonderful thing.

 

[jfollows]

Seeing as the first bit of the M5 opened in 1962, probably taking 18 months to build, design etc another few years before that you are talking mid to late 1950s when car use was still relatively low, pre-empting growth was going to be difficult. It was still 30 years before it was widened. Same goes for the M1, took 30 years for the 2 lane section at the southern end to be widened. Amazing how hindsight is a wonderful thing.

I hadn't realised it was as early as that; I remember the M5 from before it was joined to the M6 through Birmingham since my family would drive from Poynton to my grandparents in Cheltenham, probably my first memories from about 1965, and it was a bit of a pain of a journey in bits. It took a while before we could go all the way from Holmes Chapel to Cheltenham by motorway, and I remember the trumpet junction for the M50 although we didn't take it, the first time I had cause to use the M50 I was surprised when it wasn't there any more!
What has amazed me since then is the effect of roadworks, in the early days they caused miles of tailbacks, now with narrow lanes and speed limits they seem to enable much better traffic flow with much increased traffic.

 

[computerSaysNo]

This is very similar to the traffic problem and debates you get when you play Cities Skylines (which, despite all the add-ons, is basically one big road-traffic simulator). The default/pre-built system interchange you get at the start of a new map is a cloverleaf, which as discussed above is fine for light traffic but as soon as you get a significant amount of traffic it's very easy for the whole thing to become gridlocked, especially if your heaviest flow is trying to turn right. This is because traffic turning right joins its target road before traffic already on the target road gets to its junction to let it turn right, so what you end up with is a single section of road taking traffic for multiple destinations, and you can't separate it into lanes because traffic joins on the left and then different traffic leaves on the left so there's a lot of weaving needs to be done in-between the two junctions.
I find the videos on YouTube by Yumbl very interesting and informative, Yumbl and other YouTubers will do a much better job of explaining stuff than I do.

 

[Royston Vasey]

The continental country whose roads I'm more familiar with is Portugal, but also done my share of driving in the US and Canada. As per the thread title, it seems that only under duress will UK highway engineers vary the old "bung a roundabout on top" approach.

I drove for years in the US and still do a few times a year. Clover leaves can be useful in helping flow although you see a lot of toppled trucks and cars understeering off them.

But this discussion couldn't be complete without a comparison of the high efficiency of roundabouts compared to the millions of traffic light controlled crossroads there. They make driving on anything but the biggest highways a start stop frustration. So many of these would be better as roundabouts, but American drivers very rarely see them and generally aren't used to navigating them. Which is one reason they're not used on major intersections. It would be chaos.

 

[ABB125]

What is particularly stupid is that they build new roads with grade-separation for the minor junctions, and then use roundabouts for the major connections - even worse the planned A358 dualling in Somerset will achieve the feat of having two roundabouts in close succession where it meets the M5

See also the Thetford and Sleaford bypasses. It's infuriating!

I believe that, apart from finances, part of the problem is that the design code for new roads is very prescriptive and limiting in what can be done, so pragmatic ideas like tighter loops for freeflow are very difficult to justify

There are some brilliant examples on the M50 around Dublin of what can be done in (slightly more than) the space of a standard two-bridge roundabout if you're happy to slightly reduce the standards...
https://www.google.com/maps/@53.3830707,-6.362106,724m/data=!3m1!1e3 looks like they added to the original roundabout
https://www.google.com/maps/@53.4047677,-6.3104583,604m/data=!3m1!1e3 you can just about make out the original roundabout
https://www.google.com/maps/@53.3192263,-6.3673232,494m/data=!3m1!1e3 this one also has a tram line running through it!
Meanwhile, this junction in Cork, which is like many you'd find in the UK, is being replaced with this: https://www.dunkettle.ie/media/1776/dki-labels.jpg

Some are a problem, sure. But I can't remember the last time I got stuck in significant congestion at a motorway junction roundabout. Roundabouts have advantages, too - they are simple to use, all destinations are accessible including back the way you came, and they are cheap.

Roundabouts are fine. Enormous, many-lane signalised roundabouts are less fine. If you need to signalise a roundabout, you'd be far better off replacing it with a proper signalised junction (ie: crossroads), which would be more efficient. And would you call £317 million for a bigger, "better" roundabout "cheap"? Personally I'd call it a criminal waste of money (M25/A3 junction).

And then we get to things like the just-opened consultation about dualling a few miles of the A64 east of York, and an "upgrade" of Hopgrove roundabout. See here (beware the absolutely awful "virtual consultation room", something that needs to go in the things you would ban thread):

How anyone can think this is an "upgrade" is beyond me. If the money isn't available for a proper grade-separated junction here, simply don't waste money "improving" it now because you'll only need to come back again in a few years to do it properly, and then it'll cost far more than if you'd done it properly in the first place! (Incidentally, this is another example of "grade-separated minor roads, roundabouts at major roads".)

Which bring me on to hamburger roundabouts. Just no.

~~~~~
Anyway, upthread I mentioned the Lower Thames Crossing. Here's the latest junction design for the A2/M2 junction (which unfortunately is split across two pages in the General Arrangements):

And here's the A13/A1089 junction, which is hamstrung by sunk cost fallacy (continuing to use the existing trumpet) and the fact that having a junction here means five arms need to be plugged in, always a sign of complexity:

For an amusing diversion, here is the original plan for this junction (from a decade ago). Note than up is west not north in this image. Whilst this would be totally inadequate, I'm slightly surprised there's even a trumpet on here. I'd have expected another roundabout, like this:


I also mentioned the M5/M50 junction. This is the original layout:

And this is what would have happened if the motorway to Solihull had been built:

Seeing as the first bit of the M5 opened in 1962, probably taking 18 months to build, design etc another few years before that you are talking mid to late 1950s when car use was still relatively low, pre-empting growth was going to be difficult. It was still 30 years before it was widened. Same goes for the M1, took 30 years for the 2 lane section at the southern end to be widened. Amazing how hindsight is a wonderful thing.

I appreciate that (and I think I've read somewhere that the Worcestershire County Council people responsible for the M5 went on a trip to Germany beforehand, where 2-lane roads (with sharp-ish corners) were mainly what was to be found due to the fact that they were a few decades old already!
As I said, the correct decision would have been to build the road between the M50 and M42/M40 junction, because that would also add resilience to the strategic road network, something which is rather lacking in this country compared to places like France, the Netherlands, Germany etc.

 

[bspahh]

I worked in Germany for 6 months in 1989. My closest Autobahn was the A2 near Hannover, which was 2 lanes, with no speed limit. 1km before the junction, there was a sign which had the name of the nearest hamlet, rather than the town 5 minutes down the road. Junctions had names rather than numbers, and those names were normally only shown on folding paper maps. I eventually found an ADAC road atlas which had them. 500m from the junction, there would be a sign with the name of the nearest town. For paving at a cloverleaf junction, where the aim is to accelerate up to the speed of the unrestricted traffic, they went for cobbles. I was there during the summer. Apparently, they were really bad in the winter.

For me roundabouts beat cloverleaf junctions, for the ease in following directions. Its bad enough having to work out which lane to pick in a cloverleaf junction when you get it right. If you get it wrong and then get back to the junction in a different direction, and have to work out whether you need a 270 or 540 degree turn. This is easier with a SatNav, but its not as easy as being on a roundabout, where you can always take another lap if you aren't sure of the exit.

 

[ABB125]

I worked in Germany for 6 months in 1989. My closest Autobahn was the A2 near Hannover, which was 2 lanes, with no speed limit. 1km before the junction, there was a sign which had the name of the nearest hamlet, rather than the town 5 minutes down the road. Junctions had names rather than numbers, and those names were normally only shown on folding paper maps. I eventually found an ADAC road atlas which had them. 500m from the junction, there would be a sign with the name of the nearest town. For paving at a cloverleaf junction, where the aim is to accelerate up to the speed of the unrestricted traffic, they went for cobbles. I was there during the summer. Apparently, they were really bad in the winter.

For me roundabouts beat cloverleaf junctions, for the ease in following directions. Its bad enough having to work out which lane to pick in a cloverleaf junction when you get it right. If you get it wrong and then get back to the junction in a different direction, and have to work out whether you need a 270 or 540 degree turn. This is easier with a SatNav, but its not as easy as being on a roundabout, where you can always take another lap if you aren't sure of the exit.

This is further evidence that cloverleaves aren't particularly good, but unfortunately much of Europe is stuck with them.

Can you honestly say that a roundabout is the best option for somewhere like this, this (double whammy!), this or this?

 

[NoRoute]

Going back to free flow junctions, the issue I see a lot is high-speed, high capacity dual carriageways, good public highways infrastructure being downgraded into 30-40mph access roads due to local planners allowing warehousing and housing developers to plonk roundabouts straight into the middle of dual carriageways. And often it's not just one, because there's one development with it's own roundabout, then another development comes along a bit later and further along and another roundabout goes in. The dual carriageway gets transformed from a major arterial road into a join-the-dots service road which is no longer fit for purpose

 

[ABB125]

Going back to free flow junctions, the issue I see a lot is high-speed, high capacity dual carriageways, good public highways infrastructure being downgraded into 30-40mph access roads due to local planners allowing warehousing and housing developers to plonk roundabouts straight into the middle of dual carriageways. And often it's not just one, because there's one development with it's own roundabout, then another development comes along a bit later and further along and another roundabout goes in. The dual carriageway gets transformed from a major arterial road into a join-the-dots service road which is no longer fit for purpose

Unfortunately "development" trumps everything these days (with the exception of access to National Highways maintenance depots!), strategic value is pretty much at the back of the queue (and because the traffic light sequencing is shockingly appalling, it never gets last the traffic jam...).
Recent examples include M181 (two roundabouts), A40 Witney, A38 Minworth*, A40 Gloucester, A46 Farndon (I'm not sure if construction has started here yet). Speaking of the A46 Newark bypass, that's a textbook example of British shortsightedness in every sense.

*The A38 also had some extra roundabouts added when the M6 toll was built, to "encourage" drivers to use the new road. The A5 also now has some sub-optimal junctions for similar reasons

 

[Bletchleyite]

*The A38 also had some extra roundabouts added when the M6 toll was built, to "encourage" drivers to use the new road. The A5 also now has some sub-optimal junctions for similar reasons

I've never fully understood why the situation with the A556 from the M6 to the M56 persists. If they slapped a 40 on that and the M56/M6 junction was a roundabout people could and would go that way.

You can get from the M6 to the M56 via the junction now but it's incredibly, er, roundabout (or rather two).

 

[jfollows]

You can get from the M6 to the M56 via the junction now but it's incredibly, er, roundabout (or rather two).

It was always my default route, I must have saved hours of sitting in traffic queues by using the pair of roundabouts, it's no longer on my regular routes but I'd probably still forget and go that way today, I've yet to use the new A556.

 

[Bletchleyite]

It was always my default route, I must have saved hours of sitting in traffic queues by using the pair of roundabouts, it's no longer on my regular routes but I'd probably still forget and go that way today, I've yet to use the new A556.

Didn't notice they'd bypassed and dualled it! Bit of a waste of money when you've already got a perfectly good motorway, albeit 2 sides of a triangle.

 

[Starmill]

I've never fully understood why the situation with the A556 from the M6 to the M56 persists. If they slapped a 40 on that and the M56/M6 junction was a roundabout people could and would go that way.

You can get from the M6 to the M56 via the junction now but it's incredibly, er, roundabout (or rather two).

The A556 is completely grade separated and segregated now, except for at M6 J19 where there is a signallised 'through-about' rather than true grade separation.

Absolutely no problem with any of it. From the perspective of the motorist that is.

Didn't notice they'd bypassed and dualled it! Bit of a waste of money when you've already got a perfectly good motorway, albeit 2 sides of a triangle.

All in the political pressure I'd say, the old A556 brought heavy traffic 24 hours a day close to some extremely expensive property, and past a golf course and hotel which caters only to the very wealthy.

 

[jfollows]

Didn't notice they'd bypassed and dualled it! Bit of a waste of money when you've already got a perfectly good motorway, albeit 2 sides of a triangle.

The old A556 was so heavily plugged/promoted by all the road signs it appeared that "they" were terrified of too many people discovering the simple route around the two sides of the triangle. I occasionally used the A556 westbound but eastbound was even worse, especially when you found yourself behind someone turning right into Mere Golf Club! I'm sure the replacement is much of an improvement, as Starmill says.

I used the Mere crossroads frequently N-S on the A50 and watched the traffic trundling along the A556.

 

[Bald Rick]

And yes, traffic lights are not always the answer. On a slight tangent, the traffic lights at Blindley Heath on the A22 (the Lingfield turnoff) default to red when no traffic is around. When traffic is detected, the lights turn green, so you can have the situation where the lights turn to red then straight back to green. It seems to work well - does this happen anywhere else?

Lots of places, too many to mention!

 

[ABB125]

I've never fully understood why the situation with the A556 from the M6 to the M56 persists. If they slapped a 40 on that and the M56/M6 junction was a roundabout people could and would go that way.

You can get from the M6 to the M56 via the junction now but it's incredibly, er, roundabout (or rather two).

You can indeed take the roundabout route (), but there's nothing wrong with a corner-cut. Indeed, corner-cuts such as the (now upgraded) A556 should, in my opinion, be encouraged. Especially when (in this example) traffic from the south to most of Manchester (and places beyond on the M62, depending on which way round the M60 is quicker at the time) benefits. The M69 is a more extreme example of a corner-cut, as is the M26. Both very useful.

 

[PTR 444]

I've never fully understood why the situation with the A556 from the M6 to the M56 persists. If they slapped a 40 on that and the M56/M6 junction was a roundabout people could and would go that way.

You can get from the M6 to the M56 via the junction now but it's incredibly, er, roundabout (or rather two).

While it’s pointless now that the A556 has been upgraded, I’ve often wondered why they never included south-east facing slip roads when the M6/M56 junction was first built? Would have probably ended up being a lot cheaper than continuously upgrading the A556 in the long run.

 

[The exile]

Seeing as the first bit of the M5 opened in 1962, probably taking 18 months to build, design etc another few years before that you are talking mid to late 1950s when car use was still relatively low, pre-empting growth was going to be difficult. It was still 30 years before it was widened. Same goes for the M1, took 30 years for the 2 lane section at the southern end to be widened. Amazing how hindsight is a wonderful thing.

Lest we think that that is a peculiarly British problem, it took over 70 years for bits of the A1 - the principal road connection between Hamburg and the Ruhr - to gain its 3rd lane, that’s assuming they’ve actually finished it in the 10 years since I was regularly driving on it.

 

[ABB125]

Lest we think that that is a peculiarly British problem, it took over 70 years for bits of the A1 - the principal road connection between Hamburg and the Ruhr - to gain its 3rd lane, that’s assuming they’ve actually finished it in the 10 years since I was regularly driving on it.

However, Germany has the benefit of multiple parallel(ish) routes, in this case the A7/A2 via Hanover (and arguably the A28/A31 is an alternative too).

 

[snowball]

A

While it’s pointless now that the A556 has been upgraded, I’ve often wondered why they never included south-east facing slip roads when the M6/M56 junction was first built? Would have probably ended up being a lot cheaper than continuously upgrading the A556 in the long run.

A right-turn slip road would have been extremely expensive.

The junction was already one of the most complicated in the country as a result of the slip roads they did include.

Also they may have assumed not many drivers would go round two long sides of a triangle rather than one short side.

 

[ABB125]

A

A right-turn slip road would have been extremely expensive.

The junction was already one of the most complicated in the country as a result of the slip roads they did include.

Also they may have assumed not many drivers would go round two long sides of a triangle rather than one short side.

The M6/M56 junction is quite eccentric; do you know why that design was chosen, rather than a more conventional design? Land take doesn't appear to be an issue here

 

[Starmill]

The M6/M56 junction is quite eccentric; do you know why that design was chosen, rather than a more conventional design? Land take doesn't appear to be an issue here

The need to interact with the historically very important truck stop and the A50 to Warrington and the local road to Lymm made any conventional design essentially impossible.

The truck stop, which now also caters for cars too, has to be located there because that's the only place it can serve traffic on the M56 as well as the M6. Without it there would be no service station between Manchester and Chester at all.

 

[MotCO]

The M6/M56 junction is quite eccentric; do you know why that design was chosen, rather than a more conventional design? Land take doesn't appear to be an issue here

Having looked at it, the strange thing about it is that there is no direct link between the northbound M6 and eastbound M56 (without going through the two roundabouts), and the reverse. Presumably it is not a major flow.

 

[Bletchleyite]

Having looked at it, the strange thing about it is that there is no direct link between the northbound M6 and eastbound M56 (without going through the two roundabouts), and the reverse. Presumably it is not a major flow.

The thing that's odd is that it isn't a major flow as London to Manchester is the biggest intercity flow (by all modes) in the UK, so it seems utterly odd that this journey wasn't provided for without leaving the motorway. The A556 has been sorted now, but when it was built I don't understand why people weren't pushed that way to avoid clogging the A556.

Satnavs would probably mess that up now, but when it was built they didn't exist.

 

[jfollows]

Having looked at it, the strange thing about it is that there is no direct link between the northbound M6 and eastbound M56 (without going through the two roundabouts), and the reverse. Presumably it is not a major flow.

It's not a major flow because all the signs directed through traffic to the A556, so it was only those "in the know" who knew that it was trivial to go to the M6/M56 junction and use the two roundabouts. If too many people had "discovered" this alternative route the relatively trivial junction would have become clogged with traffic very quickly.
My experience was very simply that I discovered how bad the A556 used to be, so tried out this alternative route, and never stopped using it - in my case always eastbound, sometimes westbound (eastbound required two treks round two large roundabouts with lots of lanes and traffic lights, westbound was much more simple in both cases).
I stopped working near Warrington in 2015 so I no longer have a reason to use the route - and in fact I only really used it when I lived in Manchester before 2008, now that I live in Wilmslow I exit M6 at J18 when driving north along the M6 towards home.
But by all accounts the new A556 works well, and it's certainly something I felt was needed from my experience with the old road.

 

[Bletchleyite]

But by all accounts the new A556 works well, and it's certainly something I felt was needed from my experience with the old road.

What's more surprising is that given the huge flow from London to Manchester that a spur (at the time probably A556 (M) or M556, I suspect) wasn't built to the M56 towards Manchester from day one. Was it anticipated Manchester traffic would go via the M62? Or was London to Manchester traffic much lower back then?

 

[jfollows]

What's more surprising is that given the huge flow from London to Manchester that a spur (at the time probably A556 (M) or M556, I suspect) wasn't built to the M56 towards Manchester from day one. Was it anticipated Manchester traffic would go via the M62? Or was London to Manchester traffic much lower back then?

I suspect the latter, along with a view that the A556 was "good enough" and inadequate anticipation of future traffic growth plus a desire to save money. The A556 was always terrible in my driving lifetime but when the M56 was opened (by 1972 I think as far as the link from Manchester to the A556 junction is concerned, I was 10 years old then) it was probably a significant improvement over what had not been there before.