In the US, however, road racing actually saw a decline. The IMSA GT Championship had been prototype-based since 1983, with less emphasis on production cars. NASCAR was becoming increasingly dominant, and the IndyCar Series' split from CART in 1996 put more emphasis on ovals regarding domestic open-wheel racing. Also contributing to the decline was the retirement of Mario Andretti from Formula One. It would be over a decade before another American driver would join Formula One, viz. Scott Speed, although Speed was ultimately unsuccessful and eventually joined NASCAR himself.