Underground Bike Racing
What began as a bike messenger competition has grown into a popular urban sport for cyclists in general. Originally called alley cat racing, these events were held without permits and in city traffic. The object was to mimic the courier's day -- going to several destinations while figuring out the best route in the shortest time, by any means necessary.
Today, these races can be very organized and completely legal. There's even a Cycle Messenger World Championship. A documentary about the sport -- Line of Sight -- came out on DVD in winter of 2011. Racers meet at a predetermined spot and race from checkpoint to checkpoint, doing whatever they can to get there the fastest [source: Averill].
Even if the bike race is legal, the cyclists often do illegal things in the name of speed, like grabbing on to car bumpers, riding on the sidewalk (which is illegal in many cities), riding against the flow of traffic, and cutting through private property. Not to mention just riding recklessly. Stunts like hitching a ride on a taxi's bumper to get a speed boost can help racers pull ahead, but they're also very dangerous, which is why underground bike racers sometimes end up in jail.