SFI Question

DRIVER RESTRAINT SYSTEM
Seat belt mandatory in all cars. Three-inch driver restraint system
meeting SFI Spec 16.1 mandatory in any car running 11.49 (*7.35)
or quicker, in convertibles running 13.49 (*8.25) or quicker, and all
dune-buggy-type vehicles running 12.00 (*7.50) or slower. SFI 16.1
restraint system, when required, includes crotch strap and must be
updated at two-year intervals from date of manufacture.

the when required.......