Answer
**Answer: CART (Championship Auto Racing Teams)** Jan Magnussen competed full-time in the Champ Car World Series, known as CART, in the United States. CART was a premier open-wheel racing series in North America, featuring high-powered, single-seater race cars competing on oval tracks and road courses. Magnussen participated in CART from 1997 to 2004, where he achieved notable success, including race victories and podium finishes.