Many more tri-levels
were built for auto-train in 1976, but with smooth sides.
To unload the
carrier, each end door would fold twice and swing out of the way.
The yellow "bridges" would swing down to create a temporary
connection between two adjoining carriers. Autos would then be driven
out, passing through as many carriers as necessary to reach the
loading ramp on the auto dock. More
on that here...