I was at the Helmet Shop in Daytona last week, and saw a several examples of the flip up helmets. HJC makes 2 examples of this style.

Snell does not certify any of the flip up helmets.

From the Snell website:

Why won't Snell certify some types of helmets like flip up front designs?
Snell does not dismiss out of hand any helmet design that strays from the conventional. Snell does not point out any design specifications other than general requirements in our standards. We are however, always concerned with innovations and new designs that may effect the helmet's ability to protect the wearer, or in some cases the helmets potential to cause injury. At present the Foundation has not had the opportunity to test any of the flip up front type helmets for certification. We do not find any fault with these designs as long as they are used according to the manufacturers instructions and meet all of the requirements of the standard. We will also certify any size of helmet as long as it meets the same requirements as any other Snell certified helmet.