What is the primary purpose of runway edge lights?

The primary purpose of runway edge lights is to outline the runway during low visibility conditions. These lights are installed along the edges of the runway to provide clear visual guidance to pilots as they approach and land, particularly when visibility is compromised due to weather conditions such as fog, rain, or darkness. By defining the runway's perimeter, edge lights help ensure that aircraft remain on the correct path and do not stray off the runway, thus enhancing safety.

While aiding in approach during landing and signaling taxiway locations are important aspects of ground and approach lighting systems, they do not specifically target the primary function of runway edge lights. Similarly, indicating distance remaining is a role associated with other types of lights, such as distance markers, and is not the main purpose of runway edge lights.