A documentary on how the railways moved freight in the 1950s, complete with period touches of "Women: Know your place" in the commentary.
As the BFI page on the film says:
At the time, the film would have been seen as a triumphant demonstration of the efficiency and efficacy of British Railways' freight services, and the commentary implies that the system was so vital to the running of the economy that it would probably need to expand indefinitely to keep up with consumer demand.
However, hindsight reveals that the freight express's days were numbered even then. Many services were axed following the 1963 Beeching Report, and Bristol's huge Midland Road goods depot, where the early part of the film was shot, was closed in 1967.