Hot box warning came too late for Norfolk Southern train that derailed in Ohio

Norfolk Southern hot box detectors recorded increasing bearing temperatures on the car suspected of causing the disastrous derailment in East Palestine, Ohio, the National Transportation Board said today in its preliminary report on the Feb. 3 wreck.

But the temperature readings never reached the critical threshold that would have tripped an alarm and required the crew to stop the train — until moments before the derailment, when train 32N passed the detector at milepost 49.81 in East Palestine.

“Train 32N passed three [hot box detector] systems on its trip before the...