Which of the following is a function of the door hold closed switch?

The function of the door hold closed switch is to remove control of the doors from the control panels, ensuring that the doors remain closed during critical operations, such as when the train is in motion or during certain safety-sensitive situations. By engaging this switch, the crew can prevent inadvertent door operation, which is essential for passenger safety and operational efficiency. This feature is particularly important in preventing the doors from being opened while the train is moving, thereby safeguarding both passengers and crew.

The other options refer to different functionalities that do not align with the primary role of the door hold closed switch. For instance, activating the emergency brake is a distinct function intended to reduce the speed of the train upon emergencies, while allowing the doors to open automatically pertains to the normal operation of door controls rather than maintaining them in a closed state. Finally, the operation of interior lights is handled separately from door control mechanisms and has no direct connection to the function of the door hold closed switch.