Major Road Junctions Discussion, and Comparison Between UK and Other Countries

[ABB125]

Following on from the London Ringways thread, the topic of cloverleaf junctions came up.
For those of you who haven't (yet!) reached the point where road junctions are a really exciting topic (), here's a diagram of one for you to look at:

There are only two examples in the UK, in Redditch and in Livingston (the next junction north from this used to also be a cloverleaf, but for some reason was changed to what it's like now). Neither are on what could be termed as fast, high capacity or strategic roads, which may explain their limitations. In continental Europe and North America however, they are very common: in Germany, for example, it's very difficult to find a 4-way Autobahn junction which isn't either a cloverleaf, used to be a cloverleaf but has since been upgraded, of is a cloverleaf-derivative - and these examples are often only different because of limiting geography, such as this one. There are also amusing examples, such as here, where the road was quite clearly meant to continue north through the cloverleaf, but was never built, resulting in a bodge.
The main issues with cloverleaves are that traffic coming off one loop has to cross over traffic leaving via the next loop, with horrendous consequences for capacity as a result, the tight loops, and the large land-take. They are, however, easy and cheap to build (only one bridge): I think this is the main reason why they're so prevalent in countries like Germany with very old motorway networks - there are comparatively few engineering challenges. And the land take isn't too much of an issue: if you were a 1930s German landowner, would you say nein to der Fuehrer? Probably not! In the USA, land is plentiful, hence the large number of cloverleaves.
The weaving problems caused by cloverleaves can be substantially reduced by adding parallel carriageways for turning traffic - virtually all German cloverleaves have been upgraded in this way. You can even do this - a fully grade-separated cloverleaf - but obviously that's only been done because ripping out the existing junction and replacing it with something more suitable would be far too disruptive.

Having rambled on for far too long by now, I've forgotten the point I was going to make! Hopefully someone will find this interesting, and subsequent replies may cause my memory to start working again!

(This thread isn't just limited to cloverleaf junctions, by the way, fee free to discuss other designs!)

 

[LSWR Cavalier]

Some of the German junctions are a bit queer, I remember a long straight bit, then a surprising sharp cobbled curve, not so many years ago. After ww2 a lot of railways were singled, some motorways too.

 

[ABB125]

Some of the German junctions are a bit queer, I remember a long straight bit, then a surprising sharp cobbled curve, not so many years ago. After ww2 a lot of railways were singled, some motorways too.

Do you mean something a bit like this or like this? Or the fact that the older German Autobahns are built using the "straight lines and sharp bends" principle? They like their very tight-radius loops, especially in cloverleaves (as well as their 3-way cousins, the trumpet junction), although more modern junctions such as this one are better.
I do remember reading somewhere about singled German Autobahns, but I think they've all been re-dualled by now (or the second carriageway actually built!).

 

[nlogax]

Probably not! In the USA, land is plentiful, hence the large number of cloverleaves.

The US initially went with cloverleaves for the reasons you outlined, but soon learned that instead of keeping things simple they had the scope and budgets to make things as fiendishly complex and nightmarish as possible. The complex of interchanges in the vicinity of the NJ Turnpike, I-78, US1&9 and Newark Airport is by far my favourite. As a once-regular user of this concrete spaghetti it was pretty insane to navigate. No combination of free-flowing ramps could ease the traffic snarl-ups, and for those new to the interchanges or for those who didn't possess quick road wits it was confusion city and caused no end of accidents.



I rather love it, though it's much nicer to look at from above than from the driver's seat. In spite of myself I always admire the US tendency to let rip with complex road infrastructure almost on a 'because we can' basis. You have to wonder how the UK would have dealt with a similar setup. Half a dozen tri-stacked roundabout junctions a la the M25 / A3?

 

[ABB125]

The US initially went with cloverleaves for the reasons you outlined, but soon learned that instead of keeping things simple they had the scope and budgets to make things as fiendishly complex and nightmarish as possible. The complex of interchanges in the vicinity of the NJ Turnpike, I-78, US1&9 and Newark Airport is by far my favourite. As a once-regular user of this concrete spaghetti it was pretty insane to navigate. No combination of free-flowing ramps could ease the traffic snarl-ups, and for those new to the interchanges or for those who didn't possess quick road wits it was confusion city and caused no end of accidents.

View attachment 94058

Funnily enough, that's the first bit of American road I've ever been on (on a coach into New York from the airport)! As is my custom, I opened Google maps to look at what route we might take. I then took a deep breath, and tried to make my brain start working properly, given that as far as my body was concerned, it was gone 0100!

I rather love it, though it's much nicer to look at from above than from the driver's seat. In spite of myself I always admire the US tendency to let rip with complex road infrastructure almost on a 'because we can' basis. You have to wonder how the UK would have dealt with a similar setup. Half a dozen tri-stacked roundabout junctions a la the M25 / A3?

M25/A3 is perhaps the epitome of the uselessness of British roads. Even more so with the proposed "upgrade": hmmm, how about we replace the existing roundabout with a slightly bigger roundabout, that's sure to work. Not.

 

[Bayum]

I play a lot of city skylines so road junctions are well discussed on Discord and Reddit. Some of the more interesting ones are ‘Diverging Diamond Interchanges’ whereby traffic is routed onto the opposite direction of travel over a highway. This enables traffic to exit and enter the junction and immediately join the flow of traffic in the same direction. At the other end of the junction, the direction reverts to normal. Very effective.
DDI demonstration

 

[LSWR Cavalier]

@ABB125
Neither example, it was many years ago. Actually the merging junctions with two lanes often work well if vehicles are spread out, doing the same speed. One has to change lanes quick, else one lands back on the route one just left, or heading back towards where one started.

Would you like to extend your studies to Autobahnkirchen, motorway churches? There are many in Germany, for example at the Dummer Berge services. Are motorway churches a thing in other countries?

Not to mention the almost poetic names of motorway junctions, Horster Dreieck, Maschener Kreuz..

 

[ainsworth74]

I've always liked this junction between the A1M and the M18 personally. It's easy to use, not especially confusing and flows very well unless the A1M is snarled up and if it is then if you're coming from the M18 you can just carry on and try and go around the problem area. I recall once reaching the junction heading from the M1 to A1M and finding a huge queue of traffic waiting to join the A1M so we just continued up to the M62 (having seen the massive jam on the A1M as we went over) and then joined the A1M at Ferrybridge where it was once again flowing smoothly (may not have been quicker but it was nicer than just sitting in traffic!).

 

[ABB125]

I play a lot of city skylines so road junctions are well discussed on Discord and Reddit. Some of the more interesting ones are ‘Diverging Diamond Interchanges’ whereby traffic is routed onto the opposite direction of travel over a highway. This enables traffic to exit and enter the junction and immediately join the flow of traffic in the same direction. At the other end of the junction, the direction reverts to normal. Very effective.
DDI demonstration

Far too innovative and radical to be used in the UK; I mean, drivers might get confused by such a complicated layout...
(It actually says in the Design Manual for Roads and Bridges that multiple exits in quick succession should not be used because it's too complicated for drivers. Hmmm....)

@ABB125
Neither example, it was many years ago. Actually the merging junctions with two lanes often work well if vehicles are spread out, doing the same speed. One has to change lanes quick, else one lands back on the route one just left, or heading back towards where one started.

I think it helps that most Germans will know the best way to drive round a cloverleaf, and will have lots of experience doing so; British people, not so much!

Would you like to extend your studies to Autobahnkirchen, motorway churches? There are many in Germany, for example at the Dummer Berge services. Are motorway churches a thing in other countries?

I've never heard of those, do tell more.

Not to mention the almost poetic names of motorway junctions, Horster Dreieck, Maschener Kreuz..

I think German lends itself to names like this; in English, things like "Barnsley South Interchange" just sound a bit bland.

I've always liked this junction between the A1M and the M18 personally. It's easy to use, not especially confusing and flows very well unless the A1M is snarled up and if it is then if you're coming from the M18 you can just carry on and try and go around the problem area. I recall once reaching the junction heading from the M1 to A1M and finding a huge queue of traffic waiting to join the A1M so we just continued up to the M62 (having seen the massive jam on the A1M as we went over) and then joined the A1M at Ferrybridge where it was once again flowing smoothly (may not have been quicker but it was nicer than just sitting in traffic!).

How can you possibly say you like a stackabout junction? That's an offence punishable by burning at the stake!
Though to be fair, stackabouts can be fine when the volumes of turning traffic aren't too high; it's just unfortunate that they get used in totally unsuitable places in the UK. Simister Island, or Wisley Interchange, for example. They can be improved by adding extra sliproads, like at Lofthouse, Darenth and Swanley, but the cost of doing so is fairly prohibitive as it vastly complicates the junction.
If on the other hand you'd said "I really like the junction next to Ferrybridge power station", I'd have to agree with you!

What are your thoughts on the A19/A66 junction in Middlesbrough, which I'm guessing is your nearest big junction?

 

[LSWR Cavalier]

@ABB125
Have a look at 'road churches' on wikipedia, you can click on the language icon for the German version with more pictures. Strange to be in a holy place with so much noise outside.

Leeds was going to be The Motorway City of the Seventies, perhaps the M62/M1 junction is the ultimate. One of my favourites is the four-lane bit of the M62 going up hill near Huddersfield. Or where the M62 crosses the A1, there is sign 'The North, The South'

 

[ABB125]

@ABB125
Have a look at 'road churches' on wikipedia, you can click on the language icon for the German version with more pictures. Strange to be in a holy place with so much noise outside.

Interesting, I wonder why such churches don't exist in Britain? Possibly because in Germany (and other European countries) they have fairly frequent rest areas (basically just a posh lay-by), whereas here we only have full-size service stations every 30 miles or so?

Leeds was going to be The Motorway City of the Seventies, perhaps the M62/M1 junction is the ultimate. One of my favourites is the four-lane bit of the M62 going up hill near Huddersfield. Or where the M62 crosses the A1, there is sign 'The North, The South'

Leeds is interesting as it has a half-built urban motorway system (with the usual mistake of having junctions far too close to each other). Then at some point they decided "no more", and started building huge traffic-light junctions which probably take up more space than had they been grade-separated!

 

[ainsworth74]

What are your thoughts on the A19/A66 junction in Middlesbrough, which I'm guessing is your nearest big junction?

Outside of the peaks it's very good. Easy enough to navigate without any real drama and flows smoothly. But in the peaks it's a pain in the rear as there's just so much traffic wanting to use the roads that it just backs up. For instance in the morning the A66 eastbound towards Middlesbrough will be so busy that traffic coming from the A19 will end up stacking up on the two slip lanes trying to merge first into each other and then onto the A66 itself. You can have similar issues in the evening with traffic wanting to go north on the A19 jamming up on the A66 slips as that traffic cannot join easily. Whilst the slips in question are general fairly long they're not long enough so before too long you'll have traffic spilling onto the main road causing traffic there to build up and before you know it queues as far as the eye can see.

I suspect it's a junction which is fine from a usability point of view but is just exceeding it's capacity in the peaks meaning that it's snarling traffic up quite badly.

 

[ABB125]

Outside of the peaks it's very good. Easy enough to navigate without any real drama and flows smoothly. But in the peaks it's a pain in the rear as there's just so much traffic wanting to use the roads that it just backs up. For instance in the morning the A66 eastbound towards Middlesbrough will be so busy that traffic coming from the A19 will end up stacking up on the two slip lanes trying to merge first into each other and then onto the A66 itself. You can have similar issues in the evening with traffic wanting to go north on the A19 jamming up on the A66 slips as that traffic cannot join easily. Whilst the slips in question are general fairly long they're not long enough so before too long you'll have traffic spilling onto the main road causing traffic there to build up and before you know it queues as far as the eye can see.

I suspect it's a junction which is fine from a usability point of view but is just exceeding it's capacity in the peaks meaning that it's snarling traffic up quite badly.

A lot of those problems should be alleviated by the planned upgrade (including a new bridge across the Tees); following the upgrade, the junction will have (I believe) the unique status of the only non-motorway 4-way junction in the UK with at least 4 lanes in each direction on all four approaches!

 

[Domh245]

The Kegworth interchange is a bit intimidating, especially if you take in the full complex of M1/A50/A453/A42. There's also some rather interesting non-motorway roundabouts in Bramcote (running the A52 through the middle of it) and this masterpiece north of UoN's Jubilee Campus.

 

[Merle Haggard]

M6 J6 isn't a proper cloverleaf, but it connects the M6 with the Aston Expressway, Tyburn Road and Lichfield Road/Gravelly Hill and you can connect in every permutation (I think). That's one more road than a cloverleaf.
The most interesting move is from the Northbound A5127 Lichfield Road to the Southbound M6. I didn't think it was possible, but it is!
Go under the M6 and at the roundabout straight afterwards take the first exit. This takes you under the Gravelly Hill side of the Aston expressway. At the next roundabout, which is under the M6, the Southbound M6 to A38M link AND the A38M to Southbound M6 link (three overbridges - all at different heights) go through 270 degrees and up the (steep) slip road. and you are on the Southbound M6. And your passenger might be feeling dizzy...

 

[ABB125]

The Kegworth interchange is a bit intimidating, especially if you take in the full complex of M1/A50/A453/A42.

Apart from the fact that there's no direct sliproad from M1 northbound to A50 (you have to use the roundabout; I'm surprised they didn't add a sliproad during the recent upgrade, given the decent job they did on the southbound side), it's quite a good example; I'm just trying to imagine it as a series of roundabouts!

There's's also some rather interesting non-motorway roundabouts in Bramcote (running the A52 through the middle of it) and this masterpiece north of UoN's Jubilee Campus.

Ah yes, the throughabout and longabout respectively! Also known as a cheap bodge that costs more money long term...

M6 J6 isn't a proper cloverleaf, but it connects the M6 with the Aston Expressway, Tyburn Road and Lichfield Road/Gravelly Hill and you can connect in every permutation (I think). That's one more road than a cloverleaf.
The most interesting move is from the Northbound A5127 Lichfield Road to the Southbound M6. I didn't think it was possible, but it is!
Go under the M6 and at the roundabout straight afterwards take the first exit. This takes you under the Gravelly Hill side of the Aston expressway. At the next roundabout, which is under the M6, the Southbound M6 to A38M link AND the A38M to Southbound M6 link (three overbridges - all at different heights) go through 270 degrees and up the (steep) slip road. and you are on the Southbound M6. And your passenger might be feeling dizzy...

An excellent example of a tight-loop but free-flow junction. I think this sort of thing is more common on the continent, and especially across the Atlantic!

 

[Bald Rick]

There are only two examples in the UK, in Redditch

Well I never knew that. I did all four leaves of the Redditch one as a learner, having spectacularly taken a wrong turn and needing to get back on course!

You can even do this - a fully grade-separated cloverleaf

Driven through that one too.

M25/A3 is perhaps the epitome of the uselessness of British roads.

My Dad would agree, he said it was rubbish when we went on it the day it opened in 1983.

M6 J6 isn't a proper cloverleaf, but it connects the M6 with the Aston Expressway, Tyburn Road and Lichfield Road/Gravelly Hill and you can connect in every permutation (I think). That's one more road than a cloverleaf.
The most interesting move is from the Northbound A5127 Lichfield Road to the Southbound M6. I didn't think it was possible, but it is!
Go under the M6 and at the roundabout straight afterwards take the first exit. This takes you under the Gravelly Hill side of the Aston expressway. At the next roundabout, which is under the M6, the Southbound M6 to A38M link AND the A38M to Southbound M6 link (three overbridges - all at different heights) go through 270 degrees and up the (steep) slip road. and you are on the Southbound M6. And your passenger might be feeling dizzy...

I used to do that every day - pretty simple once you have worked it out. There’s only the one roundabout though...

 

[biko]

The US initially went with cloverleaves for the reasons you outlined, but soon learned that instead of keeping things simple they had the scope and budgets to make things as fiendishly complex and nightmarish as possible. The complex of interchanges in the vicinity of the NJ Turnpike, I-78, US1&9 and Newark Airport is by far my favourite. As a once-regular user of this concrete spaghetti it was pretty insane to navigate. No combination of free-flowing ramps could ease the traffic snarl-ups, and for those new to the interchanges or for those who didn't possess quick road wits it was confusion city and caused no end of accidents.

View attachment 94058

I rather love it, though it's much nicer to look at from above than from the driver's seat. In spite of myself I always admire the US tendency to let rip with complex road infrastructure almost on a 'because we can' basis. You have to wonder how the UK would have dealt with a similar setup. Half a dozen tri-stacked roundabout junctions a la the M25 / A3?

Wow, that's really complex. They really had some spare concrete it seems.

I play a lot of city skylines so road junctions are well discussed on Discord and Reddit. Some of the more interesting ones are ‘Diverging Diamond Interchanges’ whereby traffic is routed onto the opposite direction of travel over a highway. This enables traffic to exit and enter the junction and immediately join the flow of traffic in the same direction. At the other end of the junction, the direction reverts to normal. Very effective.
DDI demonstration

The flow is indeed very clever, but the downside is that you have traffic driving on the left while normally on the right (or vice versa). That is potentially very confusing and that is the reason they are not allowed in the Netherlands and many other countries on the continent I believe. Although I read something about one being built in France recently.

The Kegworth interchange is a bit intimidating, especially if you take in the full complex of M1/A50/A453/A42. There's also some rather interesting non-motorway roundabouts in Bramcote (running the A52 through the middle of it) and this masterpiece north of UoN's Jubilee Campus.

That first one looks very elegant to me. It is simple and therefore well understandable if you're a driver.

Something I've always found interesting is the difference in roundabout design between UK and the Netherlands (and other countries on the continent): the angle at which the roads are connected. British roads really let you drive fast on and off the roundabout, while Dutch and French roundabouts are really slow as the turns are tight. I think diameters are also often larger in the UK. Take for example this typical one in the Netherlands. For the category strange roundabouts, I present this one with 4 roads and an additional cycle path directly on the roundabout or this 'cycle roundabout' (have a look at Street View, otherwise not so clear).

 

[61653 HTAFC]

Leeds was going to be The Motorway City of the Seventies, perhaps the M62/M1 junction is the ultimate. One of my favourites is the four-lane bit of the M62 going up hill near Huddersfield. Or where the M62 crosses the A1, there is sign 'The North, The South'

Lofthouse Interchange (M1/M62) is a good one I agree, though better for some interchanges than others! Likewise Simister Island (M60/M62/M66) is nice and simple if you're going straight on or turning left, but if you're turning right it's a bit more tricky as you have a roundabout to deal with while still technically on a motorway. Would cloverleaves be better than either of these? In my opinion no, especially considering their rarity in the UK and the unfamiliarity that brings.

 

[Ediswan]

This junction in North Carolina was a bit intimidating the first time I used it: https://goo.gl/maps/5YatSe9sjn8yhwGM8

The same 'wrong side' driving as a diverging diamond, but all compressed into one set of traffic lights, with the opportunity for head-on collisions.

 

[ABB125]

Well I never knew that. I did all four leaves of the Redditch one as a learner, having spectacularly taken a wrong turn and needing to get back on course!

The Redditch one is fairly local to me, and at some point I'm going to go round all the loops just for fun; Livingston is somewhat more of a diversion to get to...
(Having never gone through the Redditch one (or indeed been to Redditch), I was driven through twice within one week in 2019 on totally unrelated journeys (both southbound) and haven't been back since. A bit like waiting for a bus: two come along at once! )

I used to do that every day - pretty simple once you have worked it out. There’s only the one roundabout though...

It's an easy mistake to make - that loop is smaller than many roundabouts, and nearly a full circle. Maybe you just can't see the last bit underneath the M6!

Lofthouse Interchange (M1/M62) is a good one I agree, though better for some interchanges than others! Likewise Simister Island (M60/M62/M66) is nice and simple if you're going straight on or turning left, but if you're turning right it's a bit more tricky as you have a roundabout to deal with while still technically on a motorway. Would cloverleaves be better than either of these? In my opinion no, especially considering their rarity in the UK and the unfamiliarity that brings.

A cloverleaf would have been awful for Sinister. One of these or these, on the other hand...

This junction in North Carolina was a bit intimidating the first time I used it: https://goo.gl/maps/5YatSe9sjn8yhwGM8

The same 'wrong side' driving as a diverging diamond, but all compressed into one set of traffic lights, with the opportunity for head-on collisions.

I think that's a single point urban interchange (SPUI). It's quite a clever design, as there are only two traffic light phases, so it's quite efficient. Also doesn't take up much room, hence the prevalence in (American) built up areas. This junction in Birmingham is some sort of hybrid between an SPUI and a normal diamond (not that you can really tell!).

 

[Ediswan]

I think that's a single point urban interchange (SPUI). It's quite a clever design, as there are only two traffic light phases, so it's quite efficient. Also doesn't take up much room, hence the prevalence in (American) built up areas. This junction in Birmingham is some sort of hybrid between an SPUI and a normal diamond (not that you can really tell!).

Thanks, that matches. Rather like Hanger Lane in London, ??? on first encounter, no problem once familiar.

 

[ABB125]

Thanks, that matches. Rather like Hanger Lane in London, ??? on first encounter, no problem once familiar.

I suspect so, I've never driven round Hanger Lane so can't comment!

 

[Domh245]

That first one looks very elegant to me. It is simple and therefore well understandable if you're a driver.

Kegworth is pretty elegant I'll grant you, but if you've never driven it before trying to make sure you're in the right lane can be rather tricky - especially if you're also driving it when there's a fair bit of traffic both obscuring and signs/markings and making it much trickier to change lanes. The usual British technique of only putting markings on the road surface (and if you're lucky, a freestanding sign 200m before the junction at the side of the road) doesn't help - I don't see why many of the more complex junctions don't employ overhead signs

 

[ABB125]

Kegworth is pretty elegant I'll grant you, but if you've never driven it before trying to make sure you're in the right lane can be rather tricky - especially if you're also driving it when there's a fair bit of traffic both obscuring and signs/markings and making it much trickier to change lanes. The usual British technique of only putting markings on the road surface (and if you're lucky, a freestanding sign 200m before the junction at the side of the road) doesn't help - I don't see why many of the more complex junctions don't employ overhead signs

Overhead signs cost more...

 

[nlogax]

(and if you're lucky, a freestanding sign 200m before the junction at the side of the road)

But some of those signs are amazing..ly bad.

 

[ABB125]

But some of those signs are amazing..ly bad.

View attachment 94077

I believe that sign is nicknamed the "Playboy bunny sign"...

And also unique, given that at all other 3-way triangular junctions (including the one with the M5 a couple of miles further on) don't have the stupid cross-over bit (as far as I'm aware). Yet drivers seem to be able to cope with the concept of turning left in order to go right.

 

[Domh245]

But some of those signs are amazing..ly bad.

View attachment 94077

That's particularly shocking, but I was referring more to the signs like these which give specific lanes rather than general directions (which helpfully is obscured in the next streetview image along towards the traffic lights!) - that specific junction has exactly the sort of unambiguous lane marker further up, but we only ever seem to put these on motorways and some motorway-esque A roads.

Poorly signposted roundabouts and junctions is a bugbear of mine though, as it was one of the things that got me a minor in my driving test! Whilst they may not be as well optimised or capable of as much throughput, there's something to be said for the unambiguous simplicity of a single lane roundabout!

 

[biko]

That's particularly shocking, but I was referring more to the signs like these which give specific lanes rather than general directions (which helpfully is obscured in the next streetview image along towards the traffic lights!) - that specific junction has exactly the sort of unambiguous lane marker further up, but we only ever seem to put these on motorways and some motorway-esque A roads.

Poorly signposted roundabouts and junctions is a bugbear of mine though, as it was one of the things that got me a minor in my driving test! Whilst they may not be as well optimised or capable of as much throughput, there's something to be said for the unambiguous simplicity of a single lane roundabout!

I think that is done much better in the Netherlands. There aren't so many large multi-lane roundabouts as in the UK, but mostly they have clear signage, see for example this one. It has the same situation that one lane can be used for multiple directions, and is on what you would call in the UK the junction of an urban A-road with the motorway.

 

[A0]

M25/A3 is perhaps the epitome of the uselessness of British roads. Even more so with the proposed "upgrade": hmmm, how about we replace the existing roundabout with a slightly bigger roundabout, that's sure to work. Not.

I don't disagree - but think the issue is it's a junction between an A road and a Motorway - so whilst a 'free flowing' junction would have been more desirable, it would also have caused the problem of non-motorway traffic ending up on the motorway...... If you look along the M25 the motorway to motorway junctions are far better than the motorway to 'A' road junctions are.