Read this: 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.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): What may low-traffic airports use to save electricity and staffing costs?
pilot controlled lighting