For radar separation of RNAV aircraft at or below FL450, how should separation be applied?

For radar separation of RNAV (Area Navigation) aircraft at or below FL450, utilizing random route separation is the correct approach. This method takes advantage of the RNAV systems' capability to fly flexible, user-defined routes that might not follow traditional airways or fixed flight paths. Random route separation allows for optimal use of airspace, accommodating the dynamic nature of modern air traffic while ensuring that aircraft maintain safe distances apart.

This method promotes efficiency and improves traffic flow, particularly in high-density environments where traditional separation standards may not suffice. Additionally, random route separation can leverage the autonomy of RNAV-equipped aircraft, allowing them to maintain safe separation distances while flying adjusted paths tailored to real-time situational requirements.

Other methods, such as relying solely on vertical distance, fixed criteria, or specific airspace agreements, could be either too restrictive or not applicable in situations where RNAV capabilities are being utilized. Each of those alternatives might not fully take advantage of the inherent flexibility and precision that RNAV systems offer, which can lead to inefficiencies or increased congestion in the airspace.