Quote Originally Posted by indycool
IRL mandated the wheel tethers first, CART did the HANS first.
It looks like CART and the IRL mandated wheel tethers at about the same time, although it appears from this article that the IRL announcement was a week after CARTs. F1 had already been using them for a year.

http://sportsillustrated.cnn.com/mot...shes_response/