Yes. Helmet use is required (SA2015) for both drivers and passengers. The autocross course design will attempt to keep speeds below 45 M.P.H. Drivers and passengers must provide their own helmets and motorcycle helmets will not be allowed on the autocross, or road course.
Drag racing helmet standards are different. DOT motorcycle helmets are accepted in this capacity, but SA2015 helmets are also welcome (and encouraged)!