Law

• The NHTSA reports the DOT standard FMVSS 218 must be met by all helmets used by motor vehicle riders and operators. The DOT standard sets out the minimum level of performance required by the U.S. government in the event of a automobile accident.
  
  

Snell

• Snell helmet ratings are awarded independently to helmets submitted for testing by Snell-certified engineers by helmet manufacturers, according to SMF. Each country in the world has its own legal standards for helmets, SMF reports. Snell attempts to create a standard exceeding federally mandated helmet standards around the world.
  
  

Labels

• The NHTSA reports helmets approved by both the DOT and Snell are awarded a label proving they meet set standards. A label bearing the letters "DOT" is positioned on the rear of helmets, while more detailed DOT labels and Snell labels are placed inside approved helmets to provide information on the standards met.