FMVSS No. 305a (Electric-Powered Vehicles: Electric Powertrain Integrity) is a US Federal Motor Vehicle Safety Standard issued by the National Highway Traffic Safety Administration (NHTSA) that replaces the outgoing FMVSS No. 305. It establishes crash and post-crash safety requirements for the electric power train of electric-powered vehicles — covering protection against electric shock, fire, explosion, and propulsion battery electrolyte spillage — and incorporates UN Global Technical Regulation (GTR) No. 20 by reference.
Published by: National Highway Traffic Safety Administration (NHTSA), US Department of Transportation
Current edition: Final rule published in the Federal Register, 20 December 2024 (codified at 49 CFR 571.305a)
Replaces: FMVSS No. 305 (Electric-Powered Vehicles: Electrolyte Spillage and Electrical Shock Protection)
Status: Mandatory — applicability begins 1 September 2027 for vehicles with a gross vehicle weight rating (GVWR) of 4,536 kg (10,000 lb) or less, and 1 September 2028 for heavier vehicles. Small-volume manufacturers, final-stage manufacturers, and alterers are given an additional year to comply.
Scope
FMVSS 305a applies to electric-powered vehicles sold in the United States, including battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs). It sets performance requirements for protection from harmful electric shock, fire, explosion, and gas venting during normal vehicle operation and during and after a crash, and applies to both light vehicles and heavier vehicles, with a later compliance date for the latter.
Key Requirements
- Electrolyte spillage and electrical isolation limits: aligned with UN GTR No. 20
- Post-crash electrical safety: high-voltage isolation resistance, physical barrier protection, and low-voltage limits after a crash test
- Propulsion battery integrity: requirements for the traction battery during and after a crash
- Fire and thermal propagation warning: provisions addressing in-vehicle battery fires
- Incorporation by reference: UN Global Technical Regulation (GTR) No. 20, Electric Vehicle Safety
Related Rule — 49 CFR Part 561
A companion regulation, 49 CFR Part 561 (Documentation for Electric-Powered Vehicles), requires manufacturers to compile risk-mitigation documentation and submit standardised emergency response guides so first and second responders can safely handle electric vehicles after a crash. The compliance date for this documentation requirement was 22 December 2025.
Related Standards
- UN GTR No. 22 — In-vehicle Battery Durability for Electrified Vehicles
- UN ECE R100 — equivalent international vehicle electric powertrain safety regulation
- SAE J2929 — safety standard for electric and hybrid vehicle propulsion battery systems
- GB 38031 — Chinese equivalent traction battery safety standard
Disclaimer: this is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.
References
- Federal Motor Vehicle Safety Standards; FMVSS No. 305a Electric-Powered Vehicles: Electric Powertrain Integrity — Global Technical Regulation No. 20 Incorporation by Reference, Federal Register, 20 December 2024
- 49 CFR 571.305a, eCFR
- 49 CFR Part 561 — Documentation for Electric-Powered Vehicles, NHTSA
See also: ISO 6469-1, ISO 6469-2, ISO 6469-4