Weird Harold wrote:I don't know what they used to decide, but Interstates and US Highways are designed according to a single lane width -- Ten feet, IIRC -- and not according to total width. Interstates are a minimum of two lanes wide, and modern Interstate lanes are much wider than the originals.Theemile wrote:Don't know about that, but it doesn't surprise me. (Originally) the Eisenhower system stipulated that overpasses outside urban areas had to be a minimum of several (2 or 3) miles apart. This was so that fighters and bombers could be dispersed from airbases if required and operate off any available section of highway.
AFAIK, no US highways (including Interstates) were used or planned as emergency runways. The Autobahn was designed and constructed with emergency airfields in mind, and reinforced sections of highways designated (and used in exercises) as wartime runways can be found all over Europe. But they are just sections; it isn't economically feasible to build highways entirely to the standards required of runways for jet fighters or bombers.
Remember, I said "originally" - it never made it into the official legislation, but was one of the original intentions.