One of my standard duties as the head brakeman (meaning low seniority...but I preferred riding the head end anyway) on SP freights leaving Roseville for Fresno in the Sixties was to walk the entire train, often a mile of it, from caboose to engine checking for handbrakes or anything else out of order. That's after the car knockers had presumably already done so. I found some occasionally and climbed up to release them (mostly high cars in those days, of course). The other common thing to watch for was hobos riding at the ends of shiftable loads such as pipes or lumber and suggesting they move to safer spots. I don't recall having to walk the northbound trains out of Fresno but don't recall why that wasn't necessary there.