US interchanges

[jackal]

I've compiled figures for the number of four-way full access freeflow interchanges in every US state. Here's an overall summary (no qualifying interchanges in Alaska, Hawaii, Idaho, or Montana):

The table above sums the data for several subtypes. The second table provides the more detailed raw data by subtype:

This is how I classified qualifying interchanges:

- Stack includes classic four-level stacks, stack-turbines like this, and stackmills like this.
- 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 like this 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). I subdivide offside into Offside stack, Offside 1 loop, Offside cloverstack, Offside 2 loop adjacent, Offside 3 loop, Divided (i.e., both mainlines split), Gothic (i.e. mainline(s) swap over), Other offside.

Qual refers to the total number of interchanges in the Stack, Cyclic, 1 Loop, and Cloverstack groups. This is a good measure of the number of high quality interchanges, i.e. those lacking weaving areas and offside entries/exits. Qual % is the state's percentage of the total number of quality interchanges. Qualscore is the percentage of the state's interchanges that meet the quality criteria.

I take the condition of 'freeflow' seriously, and disqualify interchanges with toll booths, pedestrian crossings, level crossings, traffic lights, at-grade long turns (i.e. left in a right hand traffic country), and four-way merges or diverges.

[WHBM]

I take the condition of 'freeflow' seriously, and disqualify interchanges with ... level crossings

I think those in the UK would find the prospect of a freeflow interchange with a level crossing rather unlikely, but there's one on a Florida-836 spur, right outside Miami airport. I've only passed there a handful of times but have seen the traffic stopped for trains twice.

https://www.google.co.uk/maps/@25.80080 ... 64!6m1!1e1

There also used to be a level crossing with the Luas tramway on an M50 off-ramp at ther Red Cow in Dublin, until the tramway was rerouted in the more recent changes.

[KeithW]

Is this list for just Interstates or does it also include the State Routes ?

The reason I ask is the total for Ohio looks a little low if you include the interchanges on high quality State Roads such as SR 315 in Columbus or SR 562 in Cincinnati although I can see how a lot may be disqualified using your rules. Until it was rebuilt in the late 90's SR 315 had some terrible interchanges and getting on to 315 Northbound from the north side heading east still involves a left turn at a traffic light controlled intersection. Before it was rebuilt there was also a slip road with an (ungated) level crossing which was rather nasty when ramp metering was on if you were unwary you could end up stuck on the crossing. To be fair the trains were usually running at low speed here as the line runs through the basement of the Nation Wide Plaza car park (built on the site of the old passenger station). This caused lots of fun when an over height car container hit the entrance and the train derailed , fortunately there were no injuries.

[jackal]

It includes Interstates, State Routes, US Routes, and anything else with grade-separated junctions. Many cloverleafs were excluded, especially in the Midwest and Northeast, for various reasons (ped crossing and traffic lights are the most common).

[Peter Freeman]

- Cloverleaf includes modified cloverleafs like this as well as classic cloverleafs.

I would have thought that the main qualification to be classified as 'cloverleaf' would be four loops. So wouldn't this be one of your '3-loops' (eg. '3-loop clovermill' or '3-loop cloverturbine') ?

[jackal]

- Cloverleaf includes modified cloverleafs like this as well as classic cloverleafs.

I would have thought that the main qualification to be classified as 'cloverleaf' would be four loops. So wouldn't this be one of your '3-loops' (eg. '3-loop clovermill' or '3-loop cloverturbine') ?

Indeed it's what I call a 3 loop turbine. I can't check Google Earth right now but assume it has been upgraded from a modified cloverleaf since 2017.

The August 2016 imagery shows the four loops with the semi-direct ramp under construction: