Which of the following is NOT a safety device that should be operational at all times?

The operational status of safety devices is critical to ensuring the safety of train operations. Alerters, locomotive camera systems, and automatic train control equipment are all essential safety features designed to protect the crew, passengers, and cargo. They serve critical functions such as ensuring that the operator remains alert, providing real-time visual monitoring of the train's surroundings, and automating safety protocols that can prevent accidents.

While windshield wipers are important for visibility during inclement weather, they are not classified as a safety device in the same manner as the other options listed. Their failure might impair visibility but does not pose the same level of risk as other safety systems that directly prevent accidents or ensure the safe operation of the train. Therefore, it is acceptable for windshield wipers not to be operational at all times, distinguishing them from the other safety devices mentioned.