Which lighting system indicates the approach slope in visual landing?

The Visual Approach Slope Indicator (VASI) system is specifically designed to indicate the proper approach slope for landing aircraft. It provides pilots with visual references to ensure they are on the correct glide path as they approach the runway. The VASI utilizes a series of colored lights that are visible at a distance, guiding pilots to maintain a safe descent rate.

When pilots see a specific combination of colors (typically red and white), they can ascertain whether they are too high, too low, or on the correct glide path. This is essential for ensuring safe landings, particularly in low visibility conditions or during night operations.

The other options, while they might suggest various safety or performance metrics, do not specifically relate to indicating the approach slope in visual landing scenarios. Understanding the role of the VASI is crucial for airport operations and enhancing flight safety.