Mike wrote --

> I-40 was mostly laid directly on top of the former US
> highway.  So I am not surprised that any remaining stretches are not very
> long.  :(

  I-25,N-S in Colorado's eastern slope, completely replaced whatever the
old road was.  Many, many years ago.  At least by the late '50s.
  There is still Rt 36 that parallels I-70 from Kansas to Denver, among
other areas. On my trip last year it was 36 from Hannibal, MO to Denver.
  Once in a while there's a tiny stretch of concrete off to the side, about
a block or so long.  All by itself. Surrounded by land.
  Here in WV Rt 60 and I-64 are still pretty much intact.  Rt 60 is now a
local road for the  most part.
  Joe