2012 page 25 3.A.3 Driver's Helmet Support:
A forward, side, and rear helmet support system shall be used in all vehicles.
Forward movement: all cars and motorcycle streamliners shall have an engineered and tested SFI spec 38.1 type head and neck restraint system.
Lateral movement: The seat, roll cage structure or suitable restraint system, such as a restraint net, swing away bar or similar such device, shall provide restriction to lateral head movement of less than 2 in. per side inclusive of structure deflection, and at a minimum extend to the forward most portion of the helmet see Section 3.B.1.