A derny is a type of motorized bicycle used in track cycling events, particularly in motor-paced races. It features a small engine and is designed to provide a slipstream for cyclists, allowing them to reach higher speeds while conserving energy. The derny typically has a low frame and is operated by a driver who maintains a steady pace for the cyclists behind. In races, cyclists follow the derny closely, benefiting from reduced air resistance. Once the race reaches its climax, the derny pulls off the track, and cyclists sprint to the finish. This exciting format is popular in events like the Six Day Races and other track cycling competitions.