Originally Posted by KRJoyce1:
Sean,
A few others besides NASCAR & USAC Include:
Grand Am, ALMS, NHRA (Classes over 150mph I believe) F-1 and some other FIA sanctioned classes. I believe the CRA may be adding a requirement as well for some classes. IRL, does not have it in it's rules yet, but all drivers are using the Hans as is the case in ChampCar.
Ken Joyce
It was mandatory in Champ Car and IRL a year or so before it was in NASCAR