- Of 681 qualifying interchanges, 386 (57%) are cloverleafs. The next most common grouping is offside (13%), followed by 3 loop (10%), 2 loop (6%) and cloverstack (5%). Compared to the US, there are far fewer stacks but more cyclic.
- Unsurprisingly Germany 'wins' with 245 qualifying interchanges, followed by Spain (100), Italy (64) and, impressively for its size, Portugal (42). The German state of North Rhine-Westphalia has 68, which would rank it third in the EU were it a country.
- The UK has a pathetic 13. France also has relatively few (29) for its size, while Cyprus, Liechtenstein, Malta, and Slovenia have none.
- In terms of national distribution of types, the UK has most stacks (3), Belgium and Italy tie for most cyclic (5 each), while Spain has most cloverstacks (9) and 2 loop (9). Germany has most 3 loop (23), offside (23), and, of course, cloverleafs (181). Several countries tie for most 1 loop (3 each)
This is how I classified qualifying interchanges:
- Stack includes classic four-level stacks, stackturbines, and stackmills.
- Cyclic includes turbines as well as windmill/octopus-type designs.
- 1 loop refers to single loop designs, including those in a stack-like arrangement, those in a turbine-like arrangement, and those in a windmill-type arrangement.
- Cloverstack refers to design with two loops in opposite corners, including 'cloverstack classic', 'clovercorner', partially-unrolled cloverleafs, cloverturbines, and clovermills.
- 2 loop refers to designs with two adjacent loops in either a stack, corner, turbine or windmill-like arrangement.
- 3 loop refers to triple loop designs in either a stack, corner, turbine, or windmill-type arrangement.
- Cloverleaf includes modified cloverleafs as well as classic cloverleafs.
- Other nearside refers to any design lacking offside entries or exits that does not fall into any of the above categories.
- Offside refers to any design with one or more offside entries and/or exits, which I define broadly to include junctions where one of the mainlines merges or diverges (e.g. this). The Offside category includes Offside stack, Offside 1 loop, Offside cloverstack, Offside 2 loop, Offside 3 loop, Divided (i.e., both mainlines split), Gothic (i.e. mainline(s) swap over), and Other offside.
Quality refers to the total number of interchanges in the Stack, Cyclic, 1 Loop, and Cloverstack categories. This is a good measure of the number of high quality interchanges, i.e. those lacking weaving areas and offside entries/exits. Quality % is the country's percentage of the total number of quality interchanges. Qualscore is the percentage of the country's interchanges that meet the quality criteria. Spain has most Quality interchanges (17), followed by Italy (12) and Germany (12), while the UK has the highest Qualscore (85%).
The table above sums the data for several subtypes. The second table provides the more detailed information by subtype (EFTA in yellow):