Tom:
Wasn’t SP still using retainers on Cajon Pass into the late ‘80’s? I remember there was a potash train ran away and piled up at the western foot of the pass. Took out a bunch of houses and damaged a natural gas pipeline that exploded not long after. It’s been quite awhile but I recollect comments at the time the crew had failed to set the retainers which led me to think it might still have been standard practice.
Curt
