The Snell Memorial Foundation promulgates two helmet standards for automotive applications: "Special Applications" and "Motorcycle." Although helmets possessing either rating will give you good protection on the track, they are designed to different criteria.
Briefly, in comparison to M-rated helmets, SA-rated helmets have the following advantages:
- They must meet a flammability specification; the shell, interior, face shield, and chin strap must be flame resistant and self-extinguishing.
- They must meet a more-stringent impact specification; testing simulates the repeated impact of a helmet against a roll bar or interior pillar.
- The face shield must have a positive lock, so that it cannot open accidentally in an impact.
- The helmet may have a more-restricted lateral field of vision (180° instead of 210°), allowing better eye protection.
While we've never seen anyone hurt at a drivers' school because they were wearing an M-rated helmet instead of an SA-rated one, we believe that the additional protection offered specifically against the types of impacts encountered on the track make SA-rated helmets the better choice for drivers' schools. (The full Standard for Protective Headgear is available from the Snell Memorial Foundation
.) (updated 11/5/2005)