What purpose do the green lights of the threshold lights serve?

The green lights of the threshold lights serve to indicate the start of a runway. These lights are crucial for pilots as they approach landing, helping them to visually identify where the runway begins. Threshold lights are positioned at the beginning of the runway to enhance visibility, especially during poor weather conditions or low light situations. By clearly marking this point, they assist pilots in aligning their landing approach properly, which is critical for ensuring a safe and successful landing.