What method should be used to control aircraft and movement of vehicles when radio communications cannot be employed?

The appropriate method to control aircraft and the movement of vehicles when radio communications cannot be employed is through the use of light signals. This method is particularly effective in situations where verbal communication is hindered, such as during periods of high ambient noise or when pilots and ground personnel are at a significant distance from one another.

Light signals can convey various commands or instructions clearly and effectively, utilizing specific colors and patterns to indicate different actions. For example, green lights might signal that it is safe to proceed, while red lights typically indicate a stop. This standardized system is critical for maintaining safety in environments where communication is compromised.

In comparison, while hand signals, sound signals, and visual signs can also provide guidance, they may not be as universally understood or reliable as light signals in high-stress or complicated situations. Light signals have the advantage of being visible from a distance and can be distinctly identified, making them an ideal choice for maintaining safe operations in the absence of radio communication.