What is the lowest minimum visibility authorized for takeoff when RVR is not available?

When RVR (Runway Visual Range) is not available, the lowest minimum visibility authorized for takeoff is 1/4 statute mile. This particular visibility requirement comes from regulations that dictate the conditions under which a pilot can safely conduct a takeoff. The 1/4 sm visibility standard accounts for scenarios where visual reference is necessary, ensuring that pilots can adequately see the runway and any critical surrounding elements necessary for a safe departure.

The other visibility options, while potentially applicable under different circumstances or types of operations, are higher than the minimum authorized when RVR is not available. Each figure corresponds to differing operational requirements, often related to specific aircraft types, weather conditions, or the availability of certain navigational aids. However, the standard of 1/4 sm is recognized as the minimum threshold to ensure adequate safety measures are in place for takeoff in the absence of RVR information. Having a clear understanding of these requirements is crucial for pilots in making informed and safe operational decisions.