Which of the following is NOT a requirement for ground vehicles operating near aircraft?

Ground vehicles operating near aircraft must prioritize safety and visibility, which is why requirements such as a functioning brake system and lights are essential. These features ensure that vehicles can stop when necessary and are visible to pilots and ground crew, thus preventing accidents on the airfield.

Communication is certainly important in aviation operations; however, while it is highly beneficial for vehicles to be equipped with radio communication systems, it is not strictly mandated for all ground vehicles. This distinguishes communication capability as a supportive measure rather than a fundamental requirement. In contrast, having a working horn is generally required for sound signaling in proximity to aircraft, enhancing safety awareness.

Therefore, the correct choice highlights that while communication via radio enhances operational coordination, it is not classified as a strict requirement for ground vehicles operating near aircraft, unlike the other options which address basic operational and safety standards.