What is indicated by a red sign with a white font on the airfield?

A red sign with white font on the airfield indicates a mandatory instruction. These signs are crucial for maintaining safety and operational efficiency on the airfield. Often, such signs convey commands that must be followed by all personnel and vehicles, such as "STOP" or "NO ENTRY". Ignoring these signs could result in safety hazards or operational disruptions, making it essential that all airfield users recognize and adhere to these directives.

In contrast, the other options relate to different types of information on the airfield. Vehicle traffic lanes are typically indicated by different signage that focuses on guiding vehicles through specific routes. Warning areas may use different colors or symbols to indicate hazards, while emergency access signs provide information for rapid response rather than mandatory needs. Each type of signage plays a distinct role in the overall traffic management and safety protocol on the airfield.