Airplanes.
I doubt anyone living where I do now used a train in 1950 either. When I use public transit, I take a bus which doesn't use any Interstate highways at all. My guess is that only a small percentage of the buses that go into NYC from NJ are ever on an Interstate, not counting the absurd designation of the helix into the Lincoln Tunnel as I-495.
ML/NJ
The railroads had to build their ‘road’ the trucking companies did not, Uncle Sam did, the Interstate system killed the railroads.