before the train begins its journey, the locomotives and the cars are checked. this is done by mechanical department workers, sometimes cameras and scanners are also used. some of the items certified "good to go" are things like the braking system including hand-brake release, brake application, condition of the air valves, piping and hoses, communication equipment, and many more. very much like the checklist an airline might use. when the pretrip work is done, the train is considered safe to move.