Up here in the NE you have to wear a helmet no matter how 'slow' your car is. That, and it needs to be SNELL 2005 rating
or newer.
Metal tire valve caps for all cars 13.00 and quicker. Roll bars in convertibles 13.00 or quicker (why I'd never consider a vert). Roll cage 11.00 and quicker, and a parachute 10.00 and quicker.
These are NHRA requirements. Some 'test and tune' days ***ahem Atco ahem*** they let it slide.
Coop