Cloverleaf
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The father of all four-way interchanges, Cloverleaves started appearing in the 1920s, connecting American and German motorways together. In this country they were pencilled into early plans for the motorway network in the 1950s, and the original set of motorway direction signs included a set specifically for use on this type of junction. However, better junction designs had evolved by the time we had two motorways actually crossing each other. No cloverleaf was ever built on the UK network, and today only three exist across the whole country.
Though they exist across the world, they are now widely discredited in most places. Most American states have active policies to remove them from busy routes, mostly because of the weaving problems they create (see below). In America and Germany, they are now mostly used for interchanges between motorways and main roads, and their use solely between motorways is discouraged. The earliest example was the Schkeuditzer Kreuz near Leipzig in Germany, opened in 1936 and still going strong.
Advantages
- Low construction cost as only one bridge is required.
- Both roads are fully grade separated.
Disadvantages
- Enormous land take, as redundant patches of land are left within the loops.
- Disorienting for right-turning traffic.
- Capacity is limited by 'weaving' - conflicts between exiting and entering traffic in the centre of the junction.
Variations
You can find a few near-cloverleaf junctions in the UK. In almost all the cases, they're either missing sliproads or are messed up with a roundabout. One near miss in Plymouth is only disqualified for a roundabout that breaks up a pair of sliproads in one corner, and the A3/A238 junction near New Malden in South London is only missing one of its loops. The closest thing to a cloverleaf on a motorway is Red House interchange at the northern end of the A1(M) Doncaster Bypass, which is missing a couple of loops and not a lot else.
Where to Spot Them
There are only three cloverleaf interchanges in the UK, at the following locations.
- A441/A448/A4189 (Headless Cross, Redditch)
- A889/A705 (Livingston)
- A889/Unclassified road (Livingston)
Actually - and tragically - this is no longer true. Livingston's local council have now removed the cloverleaf at the junction of the A889 and an unclassified road, leaving just two cloverleafs in this country - and there are suggestions that the A889/A705 junction is in the firing line as soon as funding is available. Now why on earth would you want to tear up two perfectly good free-flowing junctions?
The latest news in late 2006 is that funding has not been found for removing the second Livingston cloverleaf and it looks like it's safe for now!
With thanks to Tim Kreutzer, Phil Reynolds, Michael Davidson, Dave Ryan and George Carty for information on this page.
