Roller derby is a roller skating contact sport played on an oval track by two teams of five skaters. It is played by approximately 1,250 amateur leagues worldwide, mostly in the United States.
A roller derby scrimmage in Utah (2012)
A Charm City All Stars (Baltimore, Maryland) blocker vs. a Rhode Island Riveter (Providence, Rhode Island) jammer (2008)
Two jammers (from the Oly Rollers and Rainy City) race from the jammer line (2011)
Lonestar Rollergirls in Austin, Texas, play on a banked track (2011). The jammer (wearing the starred helmet cover) is trying to pass a pivot (wearing a striped cover) with various blockers assisting.
Roller skating is the act of travelling on surfaces with roller skates. It is a recreational activity, a sport, and a form of transportation. Roller rinks and skate parks are built for roller skating, though it also takes place on streets, sidewalks, and bike paths.
People roller skating
Unidentified woman roller skater, c. 1860–1870
Roller skates in the United States around 1905
Indoor roller skating in England, 1908