Track cycling is a bicycle racing sport usually held on specially built banked tracks or velodromes using purpose-designed track bicycles. History Track cycling has been around since at least 1870. When track cycling was in its infancy, it was held on velodromes similar to the ones used today. These velodromes consisted of two straights and slightly banked turns, though they varied more in length and material than the modern 250m track. One appeal of indoor track racing was that spectators could be easily controlled, and hence an entrance fee could be charged, making track racing a lucrative sport. Early track races attracted crowds of up to 2,000 people. Indoor tracks also enabled year-round cycling for the first time. The main early centers for track racing in Britain were Birmingham, Sheffield, Liverpool, Manchester and London. The most noticeable changes in over a century of track cycling have concerned the bikes themselves, engineered to be lighter and more aerodynamic to enable ever-faster times. Track cycling has been featured in every modern Olympic Games except the 1912 Games. Women's track cycling events were first included in the modern Olympics in 1988. The sport was moved indoors since 2000 Summer Olympics in Sydney, Australia, mainly because of the hot weather. Along the decades, track lengths have been gradually reduced. Early velodromes varied in length between 130 and 500 metres long. By the 1960s, a standard length of length was commonly used for international competitions. Since 1990, international velodromes are built with a length of , though tracks of many lengths are still in use. Main centres Track cycling is particularly popular in Europe, notably Belgium, France, Germany and the United Kingdom where it is often used as off-season training by road racers who can frequently be seen at professional six-day events (races entered by two-rider teams.) In the United States, track racing reached a peak of popularity in the 1930s when six-day races were held in Madison Square Garden in New York. The word "Madison" is still used as the name for a type of race. In Japan, the keirin race format is a very popular betting sport. The sport is well-regarded, and riders are extensively trained through the Japanese Keirin School. Race formats Track cycling events fit into two broad categories: sprint races and endurance races. Riders will typically fall into one category and not compete in the other. Bicycles The bicycles used