“Under the supervision of the Federal Railroad Administration, the company has inspected all wayside detectors in the area of the incident and found they were operating as designed,” NS said. “Out of an abundance of caution, Norfolk Southern is now inspecting all of the nearly 1,000 wayside heat detectors on its system — on top of the regular inspection of the detectors every 30 days.”
https://www.trains.com/trn/news-reviews/news-wire/wayside-detectors-in-spotlight-after-norfolk-southern-derailment-in-ohio/