Which alternative can be used in lieu of Runway Visual Range (RVR)?

Runway Visual Range (RVR) provides pilots with information about the distance over which they can see the runway surface, especially important in low visibility conditions. In circumstances where RVR is not available, ground visibility can serve as an alternative measure. Ground visibility refers to the horizontal visibility at the runway surface level, which can help pilots assess whether they can see sufficient visual references to safely approach or land.

While other types of visibility, such as flight visibility or terminal visibility, offer important data for pilots, they may not accurately represent conditions directly impacting the aircraft's approach to the runway. Ground visibility is the most directly relevant alternative to RVR because it specifically assesses the visibility conditions that the flight crew will encounter as they descend toward the runway. Therefore, when RVR data is unavailable, ground visibility provides crucial information for ensuring safety during landing and takeoff operations, making it the appropriate substitute in this context.