What must an employee do if immediate access to a working radio is not available?

The correct choice emphasizes the need for safety and operational awareness in the absence of immediate radio communication. Staying within hearing range of a radio ensures that the employee can receive important communications or alerts from others, which is crucial for coordinating activities and responding to any situations that may arise, particularly in a potentially hazardous work environment.

Maintaining proximity to a radio allows the employee to be aware of any changes in operating conditions or instructions from supervisors or dispatcher, thus reducing the risk of misunderstandings or accidents. This policy underscores an overarching principle: constant communication is vital for safety and operational efficiency on railway networks, especially when technologies like radios are not immediately accessible.

The other options do not support effective communication or situational awareness in a critical work environment. Remaining silent does not address the communication gap, notifying the dispatcher may not be practical in all situations and leaving the work area could compromise safety and situational awareness.