It’s the 50th Anniversary of the U.S. Interstate System, and Living on Earth takes a ride in a 1951 Hudson along I-95 in Boston. Our chauffeur: Dan McNichol, author of “The Roads that Built America: The Incredible Story of the U.S. Interstate System.” Along the way we meet a livery driver who remembers the days before the Interstate, and a trucker who makes a pit-stop on his regular cross-country run.