The crew possibly ignored three warnings before acting.
"According to the report, the train contained a detection system that scans for temperature differences and other mechanical warnings. When it passed the first of three mileposts containing heat detectors, the suspected bearing had a recorded temperature of 38 degrees Fahrenheit above ambient temperature. By the second, it was 103 F above ambient.
By the third milepost, the suspect bearing was 253 F above the ambient temperature. Norfolk Southern’s guidelines say that if a difference between bearings on the same axle is greater than 200 F, the situation is determined to be “critical” and engineers need to “set out” the car for maintenance.
The report added that when the train passed a milepost on the east side of East Palestine, the detector transmitted a “critical audible alarm message” due to an overheated wheel bearing. The message instructed the crew to “slow and stop the train to inspect a hot axle.”
The engineer engaged the brake application to further slow and stop the train, but an automatic emergency brake application initiated, causing the train to come to a stop. The crew observed fire and smoke and notified the dispatcher of a possible derailment."
Federal safety board releases initial report on Ohio derailment - Roll Call