"The tracks are equipped with “hot bearing detectors” that assess the temperature conditions of wheel bearings on passing trains, alerting crews if wheel bearings exceed 200 degrees Fahrenheit. The train that derailed passed three sensors before it derailed, with the doomed wheel bearing first registering 38 degrees above ambient temperatures, then 103 degrees, and finally 253 degrees above ambient temperatures, the report stated.
The sensor system transmitted a critical audible alarm message directing the crew to slow and stop the train. The engineer did so, but once the train stopped the crew saw fire and smoke from derailed cars and notified the Cleveland East dispatcher of a possible derailment."
https://www.dailywire.com/news/new-details-in-east-palestine-train-derailment-revealed-in-fresh-ntsb-report