Major British interchanges

[Johnathan404]

I usually sign mine on gantries but thats fantasy. From birds eye veiws they dont seem to use gantry signs on british cloverleaf junctions...

The problem is that we don't have an cloverleafs on roads that deserve gantries. Just look at the partially-unrolled cloverleaf - the A329(M) doesn't need gantries so it signs the M4 junction with a double fork sign, whereas the M6 and M25 do so they sign theirs with gantries.

[RoadaddictReece]

Heres a very unusual gantry sign i created for a major recently created 4 way cloverleaf by the way...

[sgill77]

I've never seen one myself, but I'd imagine there would be a double-fork advance direction sign, and then individual flag signs at each gore, all denoting directions such as (E) and (W).

That's pretty much how the one at Redditch is signed, except that rather than denoting directions, they just sign the destinations. That's probably because the only road that goes through the cloverleaf is the A441; the A448 TOTSOs here, and the east-west route changes from A448 to A4189 at the cloverleaf.

[Jam35]

I've never seen one myself, but I'd imagine there would be a double-fork advance direction sign, and then individual flag signs at each gore, all denoting directions such as (E) and (W).

That's pretty much how the one at Redditch is signed, except that rather than denoting directions, they just sign the destinations. That's probably because the only road that goes through the cloverleaf is the A441; the A448 TOTSOs here, and the east-west route changes from A448 to A4189 at the cloverleaf.

I've never really got the point of all that TOTSOing, seeing as the A448 ends on the A435 anyway. It would be much simpler to renumber the A4189 (at least west of the A435) to A448, then give the orphaned section a "suspicious" number such as A4348.

[sgill77]

I've never really got the point of all that TOTSOing, seeing as the A448 ends on the A435 anyway. It would be much simpler to renumber the A4189 (at least west of the A435) to A448, then give the orphaned section a "suspicious" number such as A4348.

That would certainly make much more sense than what happens at the moment. The post-TOTSO bit of the A448 is so unconnected to the main part that it might as well have a new number - it starts further west than the east-most end of the "main" A448, and if you changed the number no-one would ever guess that they once shared one.

While we're at it, the A448/B4091 TOTSOs in Bromsgrove are a bit of a mess too.

[roadtester]

A slightly different aspect - from the original list and subsequent discussion, it appears that the UK probably has no more than 50 major grade-separated DC/M'way interchanges. Am I the only one who thinks that's a rather paltry number for a country with a population of about 60 million?

Anyone hazard a guess what the totals would be for e.g. France, Germany or Italy? Obviously Germany rules when it comes to the cloverleaf but apart from that I don't really have much of a feel for this.

[Chris5156]

How is a british cloverleaf typically signed?

Given that there are only two of them, I don't think there is anything typical about it. There is no established practice.

[owen b]

the UK probably has no more than 50 major grade-separated DC/M'way interchanges

But that's not entirely fair. Jackal's list only includes interchanges with two complete mainlines and all possible movements. There are numerous other major GSJs. Jackal's list excludes major interchanges such as M1/M25, M1/M6, M6/M6T/M42, M5/M6, M1/M18 etc. etc.

[Jam35]

M6/M6T/M42

I wonder what the technical term for that one would be...

[owen b]

M60/M61/A580 aka Worsley Interchange is another classic that doesn't make the list. There are many more.

[ForestChav]

M6/M6T/M42

I wonder what the technical term for that one would be...

A mess.

[jackal]

the UK probably has no more than 50 major grade-separated DC/M'way interchanges

But that's not entirely fair. Jackal's list only includes interchanges with two complete mainlines and all possible movements. There are numerous other major GSJs. Jackal's list excludes major interchanges such as M1/M25, M1/M6, M6/M6T/M42, M5/M6, M1/M18 etc. etc.

I've updated the list. Looks like we've come up with 49 so far. I certainly wouldn't rule out breaking the fifty barrier.

Also as Owen says my criteria are a bit more specific than my thread title suggests. I just thought it would be a pithy title and would capture the spirit of what we're talking about. I'd also mention M56/M60/A34 and the recent M62/A1(M) junction as being undoubtedly major junctions that don't satisfy the specific criteria.

Am I the only one who thinks that's a rather paltry number for a country with a population of about 60 million?

Anyone hazard a guess what the totals would be for e.g. France, Germany or Italy? Obviously Germany rules when it comes to the cloverleaf but apart from that I don't really have much of a feel for this.

I'm sure many countries have more junctions that satisfy the criteria. For example Germany both has a much larger network and has a specific policy of building in redundancy, so they'll build a full cloverleaf where we'd just put in a few movements (see thread in International). I'm sure the UK would get trounced in a comparison of the number of complete 'major junctions', but it's not entirely a fair comparison because UK planners (rightly or wrongly) view those movements as unnecesary. At any rate, the main problem with the UK network compared, e.g., to Germany is the sheer lack of motorway - any lack of four way full access junctions would just be a symptom of that.

[firefly]

The M61-A666 junction is still missing. Something like that is called a Linienlösung in german which translate literally into line-solution. The M1-A42 junction belongs to that category as well.

[J N Winkler]

A slightly different aspect - from the original list and subsequent discussion, it appears that the UK probably has no more than 50 major grade-separated DC/M'way interchanges. Am I the only one who thinks that's a rather paltry number for a country with a population of about 60 million?

On a per capita basis, yes, it is rather paltry. However, I think it is rather generous in relation to centerline miles--Britain has just 2,000 miles of motorway plus (rough estimate) an additional 1,000-2,000 miles of comprehensively grade separated dual carriageway for which it is appropriate to provide system interchanges. Of course, a rather higher density of elaborate interchanges is necessary to service a driving population of about 26 million (compared to about 200 million in the USA, with an Interstate network of circa 45,000 miles supplemented by perhaps 10,000 additional miles of state and US route freeway).

Anyone hazard a guess what the totals would be for e.g. France, Germany or Italy? Obviously Germany rules when it comes to the cloverleaf but apart from that I don't really have much of a feel for this.

It's hard to speak in terms of numbers without doing a count. My impression is that system interchanges are dense in the Netherlands and Belgium and rather less so in France, Spain, and Italy. Because so many of the long-distance comprehensively grade-separated routes in the latter three countries are toll highways, the proportion of system interchanges that are freeflow is lower, and there is a correspondingly higher fraction of double trumpets and the like.

In terms of four-level stack interchanges (deliberately restricting this category to interchanges with a Maltese cross configuration), Britain has more (3) than any other European country. Other European countries with stacks include Germany (1), Greece (at least 1), Spain (at least 1), and the Netherlands (at least 1). The USA has at least 53, in Texas (at least 25), California (9), Michigan (4), Arizona (3), Ohio (3), Alabama (3), Maryland (1, with another currently under construction), Florida (at least 1), New York (at least 1), Washington (1), Louisiana (1), and Tennessee (1).

However, interchange configuration is not the only determinant of high capacity. In order to realize the full capacity advantages of a particular design, you need to provide geometry that is as generous as practicable. It is theoretically possible, for example, to build a four-level stack which handles various movements less efficiently than some cloverleaf designs. The left-turning direct connectors in the original Four Level have curve radii which are not significantly larger than those used for the loop ramps in some cloverleaf interchanges.

[Ben302]

M2/A229? A bit doubtful, I admit, but I think the A road connecting roads to the M2 are all classified as A229 and the spirit of the thing is that the whole lot connects the M2 to the A229. Before the M2 improvements it used to be a trumpet/dumbbell combo, so this may be a rare case in this classification of a downgraded junction.

Downgraded.... The old junction used to be an absolute nightmare at the best of times. The M2 and A229 all meeting in one place and the dumbell on the a229 used to be so tight that lorries would tip on a weekly basis. the trumpet on the M2 was equally tight on the coasbound side so the new junction is miles better in terms of design aside from the many sets of lights that were put in but at least it all works.

two more for the list

Trumpet/freeflow hybrid
A2/M2/A289

Trumpet
A2/A2260

[joshurtree]

How about the old A1/M62 junction?

[owen b]

How about the old A1/M62 junction?

It's already on the list as M62/A162.

[Halstead]

Trumpet
A2/A2260

I remember that one well back then when a petrol station and Little Chef were situated to the west and you had to go down a dip and back up before crossing the A2260 junction. It's not there anymore as a new junction catering for Ebbsfleet is now there.

Another junction that I liked before it was changed was the M2/A228 junction. Back in the olden days it was the signed route into Grain before the A289 popped up but despite being a half cloverleaf it had a few special things about it. One of them being that a small road heading off the A228 goes along the bridge with the M2 before dipping into a residental road underneath the motorway. But when the CTRL link this would cease to exist and turn the road into a dumbell. There's also a OS map of c2003 featuring this junction as half dumbell, half half cloverleaf with the CTRL slicing through the dumbell side.

[Burwellian]

Girton.

Yes, the A14 splits, but the main routes through when built were the M11 -> A604 (N-S; now the A14 heading West) and the A45 (E-W; now the A14 to the East and the A428 to the West). Both flow straight into each other, with the A1307 (the A604 through Cambridge) branching off through the junction towards the south.

Not sure how to classify it though.

[jackal]

Girton is another example of something that is certainly a major interchange, but that doesn't qualify since it isn't full access. There are lots of movements to/from A1307 and A428 that you can't do.