USA: A defective wheel bearing on a hopper wagon led to last year’s derailment of a Norfolk Southern train at East Palestine, Ohio, and a subsequent fire and release of hazardous material, the National Transportation Safety Board confirmed on June 25.

Announcing the results of its investigation, NTSB said that overheated wheel bearings were a common cause of rail accidents, and detectors were provided to warn crews to stop their train before a failing bearing could cause a derailment. But on February 3 2023 the crew of train 32N did not receive a hot bearing warning until it passed over a detector at East Palestine, when the overheated bearing was about to cause an axle failure. Although the crew began to slow the train using dynamic braking, it was too late, and 38 vehicles derailed, including 11 tank cars carrying hazardous materials.

NTSB investigators explained that the difficulty of accurately measuring temperature inside the bearing, combined with Norfolk Southern’s standard operating procedures and the spacing between detectors, meant the crew did not receive sufficient warning to stop the train before the derailment occurred.

Hazardous materials

Presenting the findings at a board meeting in East Palestine, NTSB said the decision by the local incident commander three days later to conduct a ‘vent and burn’ of the vehicles carrying vinyl chloride monomer had been based on incomplete and misleading information, and was not necessary to prevent a tank car failure.

According to the Federal Railroad Administration, the procedure should be a last resort, only used when a tank car is about to fail. The investigators reported that NS had rejected three other proposals for removing the vehicle contents and began planning for a vent and burn shortly after the derailment. They felt the continued use of DOT-111 tank cars to transport flammable liquids had contributed to the severity of the hazardous materials release.

Three DOT-111 cars were mechanically breached during the derailment, releasing flammable and combustible liquids that ignited. The fire spread and exposed other tank cars to heat, leading to a decision to vent five tank cars carrying vinyl chloride. That in turn resulted in a mushroom cloud that towered over the town and surrounding area.

DOT-111 tank cars are being phased out because of their inadequate mechanical and thermal crashworthiness and a propensity to release lading in a derailment. NTSB has been calling for an accelerated phaseout of the vehicles from hazmat service, citing their ‘unacceptable’ safety record.

Safety recommendations

Following the investigation, NTSB has issued new safety recommendations to the Secretary of Transportation and industry organisations, notably FRA, the Pipelines & Hazardous Materials Safety Administration, the Association of American Railroads and Norfolk Southern Railway, as well as the fire service and chemicals industry. These recommendations address issues including:

  • failure of wayside monitoring systems to diagnose a hot wheel bearing in time for mitigation to prevent a derailment;
  • inadequate emergency response training for volunteer first responders;
  • hazardous materials placards that burned away, preventing emergency responders from immediately identifying hazards;
  • a lack of accurate, timely and comprehensive information passed to local incident commanders and state officials;
  • the continued use of DOT-111 tank cars in hazmat service.

‘Unfortunately, some have sought to minimise the wide-ranging impacts of this derailment, pointing to the fact that there were no fatalities or injuries’, said NTSB Chair Jennifer Homendy. ‘For this, we are certainly grateful, but the absence of a fatality or injury doesn’t mean the presence of safety. Our agency doesn’t wait for death or injury to occur. Instead, we objectively analyse the facts and evidence to make recommendations that, if implemented, will ensure this never happens again. Thanks to the hard work of our world-class investigators, we now have a roadmap to do just that.’

NTSB’s final report is expected to be published in the next few weeks, but the agency has made available an abstract which includes its findings, probable cause, and all of its safety recommendations.