If there is variable RVR, which value should be considered?

When assessing variable Runway Visual Range (RVR) values, the most critical value to consider is the lowest RVR. This is because the lowest RVR represents the minimum visibility conditions that pilots must operate under. In aviation, safety is paramount, and pilots need to have a conservative understanding of visibility, especially when making landing or departure decisions.

Using the lowest RVR ensures that pilots and air traffic controllers are prepared for the worst-case scenario, thereby minimizing the risk associated with reduced visibility. By focusing on this value, flight crews can make informed decisions that prioritize safety, ensuring that operations can be conducted within the established safety margins.

While the other options might seem relevant for situational awareness or understanding general conditions, they do not provide the most critical information needed for making operational decisions regarding safety in visibility-limited scenarios.