Triadic,
All IFR federal airways in the US are controlled airspace (class E) from 1200'AGL up to 18000' (class A). Class E extends down to 700'AGL at a non controlled airport with an IFR approach procedure. To operate IFR in controlled airspace, you need to file an IFR flight plan and get an ATC clearance.
I Fly,
The US airspace system works very well and is mostly supported by the interest return of an aviation development fund set up in the early part of last century.