The National Transportation Safety Board ruled Legal_rulings that the derailment Catastrophe was caused Causation by the train 's engineer ( driver ) becoming Becoming distracted by other radio transmissions and losing Earnings_and_losses situational awareness , and said Statement that it would have been prevented Preventing_or_letting by positive train control , a computerized speed-limiting system that was operational Being_in_operation elsewhere on the Northeast Corridor , but whose activation Being_in_operation at the wreck site had been delayed Hindering due Causation to regulatory requirements .