What procedure must be followed when applying a blue signal to the controls of a diesel locomotive?

Affixing the blue signal to the throttle of a diesel locomotive and ensuring it is illuminated at night is essential for safety. This procedure serves as a method of communication among crew members and indicates that work being performed on or about the locomotive requires its controls to be secured. By placing the blue signal visibly on the throttle, it ensures that anyone operating the locomotive is immediately aware that personnel may be working on it, thus preventing accidental movement which could endanger the safety of the workers.

Illuminating the signal at night enhances visibility, ensuring that its presence is easily noticed in low-light conditions. It's critical for maintaining a safe working environment, as it prevents misunderstanding among crew members regarding the status of the locomotive and ensures that all necessary precautions are observed. This procedure is part of the broader safety protocols mandated in the operating rules to protect both crew members and equipment during maintenance activities.