My conductor son tells me that DPU’s are supposed to be fully secured at a trains originating terminal.
The leader in a headend consist is generally locked from the inside by the crew. Trailing locomotives are left unlocked in the event a crewman has to pass through them to address a problem in one. Of the two cab access doors on a wide cab locomotive, only the nose door can be locked from the outside. The rear facing door behind the engineer can only be locked from the inside.
CW
