NHTSA Proposes New Standards for Converted Vehicle Safety Testing

The 25-unit annual production threshold is the right line to draw. Below that you're in hobbyist territory where individual responsibility and state inspection laws apply; above it you're a commercial operation where fleet customers reasonably expect standardized safety verification. The question of whether small conversion shops need a simplified pathway is a real one — NHTSA is right to specifically request comment on it.

FMVSS 305 and 305a adapted for conversions is the sensible starting point. The isolation resistance minimums and thermal runaway venting requirements are the technically substantive parts — these are the failure modes that cause serious injuries in EV fires, and a conversion that buries a pack in a vehicle structure not originally designed for it needs to meet at least the same standard as an OEM EV on those specific points.

The hobbyist exclusion is clear but the preamble note about state inspection programs potentially referencing federal standards is worth watching. If your state DMV informally references FMVSS 305 for title transfer on conversions — which several already do — the proposed rule matters to individual builders even though they're explicitly out of scope.