is the FIA World Endurance Championship. The main series for GT car racing is the Blancpain GT Series, divided into two separate championships: the Blancpain GT World Challenge Europe and the Blancpain GT Series Endurance Cup. This series has formed after the folding of the various FIA GT championships. Other major GT championships include the Blancpain GT World Challenge America, Blancpain GT World Challenge Asia, Super GT, and the International GT Open. There are minor regional and national GT series using mainly GT4 and GT3 cars featuring both amateur and professional drivers. Sports prototypes, unlike GT cars, do not rely on road-legal cars as a base. They are closed-wheel and often closed-cockpit purpose-built race cars intended mainly for endurance racing. They have much lower weight and more downforce compared to GT cars, making them much faster. They are raced in the 24 hours of Le Mans (held annually since 1923) and in the (European) Le Mans series, Asian Le Mans Series and the WeatherTech SportsCar Championship. These cars are referred to as LMP (Le Mans prototype) cars with LMP1 being run mainly by manufacturers and the slightly less powerful LMP2 cars run by privateer teams. All three Le Mans Series run GT cars in addition to Le Mans Prototypes; these cars have different restrictions than the FIA GT cars. Another prototype and GT racing championship exists in the United States; the Grand-Am, which began in 2000, sanctions its own endurance series, the Rolex Sports Car Series, which consists of slower and lower-cost race cars compared to LMP and FIA GT cars. The Rolex Sports Car Series and American Le Mans Series announced a merger between the two series forming the WeatherTech SportsCar Championship starting in 2014. These races are often conducted over long distances, at least , and cars are driven by teams of two or more drivers, switching every few hours. Due to the performance difference between production-based sports cars and purpose-built sports prototypes, one race usually involves several racing classes, each fighting for its own championship. Famous sports car races include the 24 Hours of Le Mans, the Rolex 24 at Daytona, 24 Hours of Spa-Franchorchamps, the 12 Hours of Sebring, the 6 Hours of Watkins Glen, and the Petit Le Mans at Road Atlanta. There is also the 24 Hours of the Nürburgring on the infamous Nordschleife track and the Dubai 24 Hour, which is aimed at