As I was standing at a crossing in Chehalis, Wa yesterday, watching a UP NB go into the yard, There was a bunch of autoracks and I happened to glance at the data placard on one, it was built in 04/1968!! So I looked at a few more and noticed quite a few were built in the early 70's as well, even though the "shell" was fresh and had almost new RR reporting marks. I thought there was a certain time limit set by the AAR for age on railcars?
I think as long as cars pass mechanical inspection, remain economical to operate (i.e. stay clear of the rip track) and are in demand, they are able to remain in service. I'm guessing that tank cars are probably the youngest cars in service, as regulatory requirements stack up against older cars. I'll bet those old auto racks have had some significant rebuilding. I recall standing trackside when rack cars were open and without roofs. My friends and I enjoyed watching the new Chevys and Fords go by, choosing which one in the train we'd like to have.
I would think that given the relatively light weight to volume ratio racks deal with, they are less subject to the wear and tear that cars handling 100 ton loads are, which may help them stay viable longer.
