What type of doors must crew members not attempt to close?

Crew members must not attempt to close plug doors because these types of doors are designed to be sealed tightly against a frame, creating a secure barrier to prevent cargo or personnel from falling or being exposed to the outside. The mechanism associated with plug doors can be complex, and improper handling could result in accidents or injury.

In the context of train operations, crew members are trained to recognize the importance of safety and proper operation of equipment. Attempting to close a plug door without proper knowledge or assistance could lead to the door becoming misaligned or malfunctioning, which could compromise the safety of both the crew and the cargo. Understanding the specific operation procedures for different door types is essential for maintaining safety during switching and handling operations.