Although you can get extensions
Many private passenger cars exceed 50 yrs old.
I've consulted several sources on the banning of older freight car underframes. For the year 1974 I found two conflicting notes:
1974 - No underframes over 40 years if built before July 1, 1974.
1974 - No underframes over 50 years if built before July 1, 1974.
So is 40 or 50 years?
And was this a ban from interchange initiated by the industry or did the federal government outlaw such older underframes?