Context: On runways, green lights indicate the beginning of the runway for landing, while red lights indicate the end of the runway. Runway edge lighting consists of white lights spaced out on both sides of the runway, indicating the edge. Some airports have more complicated lighting on the runways including lights that run down the centerline of the runway and lights that help indicate the approach (an approach lighting system, or ALS). Low-traffic airports may use pilot controlled lighting to save electricity and staffing costs.

Question: On runways, what indicate the beginning of the runway for landing?
Answer: green lights

Question: On runways, what indicate the end of the runway?
Answer: red lights

Question: What indicates the edge of a runway?
Answer: white lights

Question: What may low-traffic airports use to save electricity and staffing costs?
Answer: pilot controlled lighting

Question: What does ALS stand for?
Answer: approach lighting system

Question: What does runway edge lighting indicate for landing?
Answer: Unanswerable

Question: What marks the end of the ALS at low-traffic airports?
Answer: Unanswerable

Question: What does using an ALS help save?
Answer: Unanswerable

Question: What does pilot controlled lighting consist of?
Answer: Unanswerable

Question: What do red lights down the the center of the runway indicate?
Answer: Unanswerable