https://babel.hathitrust.org/cgi/pt?id=pst.000017394611;view=1up;seq=1
Testimony relating to Interstate highway safety in the 1960s. Some fascinating insights into how things were done in those days, the reasoning behind hidden designations, the size of the map industry in those days (250 million printed in 1967!)
That document has shown up in several threads here over the years. Lots of interesting old photos, especially for people familiar with the DC-area Interstates. Worth a look for people who like old pictures. Insanely long document to try to read the whole thing, though.
Feel free to delete the thread, in that case. Tried to search for it, but came up short.
It was extremely cool to see the old pictures of the Los Angeles area in there. I guess I never realized that what is now I-110 (and once was California 11) used to be US 6 before the renumbering. In 1964, I would still have been pooing in my diapers. :D