The event billed as "The Greatest Spectacle in Racing" is considered part of the Triple Crown of Motorsport, which comprises three of the most prestigious motorsports events in the world, also including the Monaco Grand Prix (which traditionally falls on the same day as the Indianapolis 500) and the 24 Hours of Le Mans. In two different periods, the race was part of FIA World Championships; between 1925 and 1928, the World Manufacturers' Championship and between 1950 and 1960, the Formula One World Championship. The official attendance is not disclosed by Speedway management, but the permanent seating capacity is upwards of 250,000, and infield patrons raise the race-day attendance to approximately 300,000. It shares its date with NASCAR's 600-mile event at Charlotte, with drivers having completed both events in one day before in a so-called Double Duty.