How are runway centerline lights configured for the last 3,000 feet of the runway?

Runway centerline lights are configured to enhance visibility and provide guidance to pilots during landing, especially in low visibility conditions. For the last 3,000 feet of the runway, these lights alternate between red and white. This configuration serves a critical purpose: it helps pilots determine their position on the runway and signals that they are nearing the end of the runway. The white lights indicate that pilots are on the approach to the runway's usable length, while the red lights signify that they are entering a critical phase where they should prepare for a possible go-around if they haven't landed safely, as they are approaching the runway threshold.

The other configurations, such as having all lights white or all red, do not provide the same level of differentiation and situational awareness for pilots. Having no lights in that section would render it difficult for pilots to ascertain their position, which is essential for safe landings. Thus, the alternating red and white lights are a crucial element of runway safety, especially in the last stretches of the runway.