Are airless tires legal in the United States?

Airless tires, also called non-pneumatic tires or NPTs, are generally legal in the United States for certain applications, but legality for regular passenger cars on public roads is more complex and not fully approved yet for widespread use. Airless tires like Michelin Uptis, Bridgestone Air Free Concept, and those used on military vehicles, construction equipment, lawn mowers, and bicycles are legal and already used off-road, for low-speed vehicles, and for specialty applications because they cannot go flat and require less maintenance. For passenger cars on public highways, airless tires must meet Federal Motor Vehicle Safety Standards set by NHTSA, including standards for strength, endurance, and performance, and currently no airless tire has received full DOT approval for regular highway use on passenger cars as a direct replacement for pneumatic tires, though Michelin Uptis is undergoing testing and pilot programs with GM aiming for approval. Airless tires are legal for use on certain vehicles like golf carts, ATVs, skid steers, and military vehicles on public roads where allowed. Some states have no specific law banning airless tires, but they must still be DOT approved to be street legal. So airless tires are legal for off-road and low-speed use now, and are moving toward legality for passenger cars but are not yet widely legal for highway use in US.