I would love to see a citation for that as its a very surprising number! Found it: https://www.gao.gov/products/109954 https://www.gao.gov/products/109954 A c

I would love to see a citation for that as its a very surprising number! Found it: https://www.gao.gov/products/109954 https://www.gao.gov/products/109954 A couple of caveats: it's from 1979 and deals with interstates only.