For what purpose does a blue light signal serve specifically?

A blue light signal serves the specific purpose of providing emergency communication access in the context of train operations. This signal is an important safety measure, enabling operators and crew members to quickly identify emergencies or situations that require immediate attention. When the blue light is displayed, it alerts personnel that there is a critical issue to address, such as an incident involving passengers or equipment, allowing for prompt and appropriate action.

The use of blue light signifies a level of urgency and is distinct from other signals that may regulate train speed, provide passenger information, or indicate construction warnings. Each of those other signals has its designated color and meaning, thus emphasizing the specific role that a blue light plays in emergency communication within the rail transport system.