When do SMGCS regulations go into effect?

SMGCS, or Surface Movement Guidance and Control System, regulations are specifically designed to enhance safety and control on airport surfaces during low visibility conditions. The implementation of these regulations occurs when visibility is at or below 1200 RVR (Runway Visual Range). This is crucial because pilots and air traffic controllers need specific guidelines to navigate safely when visibility is compromised due to factors such as fog, heavy rain, or other obstructions that can reduce sight lines on the runway and taxiways.

While flying over FL 290 and during thunderstorms may involve specific protocols, these don't relate directly to the activation of SMGCS regulations. The regulations are fundamentally focused on managing ground operations under low visibility, highlighting the significance of knowing when visibility drops to the critical thresholds where SMGCS becomes necessary. Thus, the correct answer encompasses the essential safety measures that are notably affected by low visibility.