The Pipeline and Hazardous Materials Safety Administration is seeking information on the safety risks, operational challenges, and regulatory considerations associated with transporting hazardous materials using heavy-duty electric vehicles (EVs) compared to internal combustion engine (ICE) motor carriers.

The notice states that PHMSA aims to understand what impact the transition from ICE to EV motor carriers may have on hazmat packaging integrity, transportation safety, emergency response protocols, regulatory compliance, and overall vehicle risk. The agency may use the information gathered to develop a statement of work for further research into the safety of transporting hazardous materials in EVs.

The notice identified several potential safety risks, including:

• Battery hazards: Lithium-ion batteries pose unique risks, including thermal runaway, fire propagation, and flammable/toxic gas emissions that differ from the hazards associated with conventional fuel sources.
• Charging station vulnerabilities: Transporting hazmat via EVs requires charging infrastructure, which may influence cargo exposure risks, spill ignition potential, and emergency shutdown procedures.
• Weight distribution and cargo stability: EV batteries add additional weight that may impact hazmat containment strategies differently than ICE motor carriers, and potentially may influence vehicle stability, packaging requirements, and load distribution.
• Emergency response adaptations: Fires, leaks, or mechanical failures in heavy-duty EVs require specialized response measures, which differ from those needed for ICE-powered motor carriers.

In November 2024, NEFI and the National Propane Gas Association sought guidance from PHMSA regarding the safe operation of hazardous materials tanks, including MC-331 tanks, on electric vehicles. The request noted that states such as California, Washington, and Massachusetts were requiring Class 7 and 8 trucks carrying hazardous materials to transition fleets in their respective states to EVs as early as January 1, 2025, and guidance on the safe construction and operation of these vehicles was lacking.

NEFI and NPGA said they were concerned that without proper guidance from PHMSA, placing a MC-331 tank on an EV could result in a catastrophic cascading fire or thermal runaway, resulting in a Boiling Liquid Expanding Vapor Explosion (BLEVE) or impinging the tank. In an internal combustion engine vehicle fire, expedited response and eliminating the fire aims to protect the tank and prevent a catastrophic incident involving the hazardous materials. However, the fire response protocol for an EV differs from that of an ICE, in that emergency response typically lets the fire burn itself out.