Editing Demolition derby (section)

== Rules ==
Derbies have many different sets of rules, often pertaining to how much welding can be done to the vehicle, and the class of car (example: compacts, trucks, minivans, full size; some rules are 1980 and newer, etc.).<ref name="LATimes07212001" /> Drivers are often required to be at least 16 years old and hold a valid driver's license. They are required to have seat belt and a helmet, and, depending on sets of rules, roll over bars and cages inside the vehicle.<ref name="LATimes07212001" /> An event usually begins with drivers lined up on the track facing rear to rear, or circling on an oval track.<ref name="LATimes07212001" /> Drivers are usually required to crash into another vehicle every 2 minutes or they are labeled as "sandbagging" and become disqualified. Hitting a driver intentionally in the driver's door and sometimes rolling another car intentionally, are also grounds for disqualification.<ref name="LATimes07212001" />

When a car is disabled or loses power, the driver is allowed time to restart their engine, usually 30 seconds to a minute, and must be able to move. If the car cannot start and move, the driver is forced to concede and is eliminated from the heat.  Most events require a slat of wood with a flag attached  to be  placed in the front column of the driver door, a judge breaks this to disqualify a driver, or a driver can break it in order to resign. The first and second place finishers of a heat move  on to the next heat, in competitions with multiple heats.

Depending on the sanctioning body, it may be illegal for multiple cars to collaborate and gang up on opposing cars in a sandwich effort, and could result in disqualification for both parties that do so; although the enforcement of this rule varies widely. The time it takes for one of these events varies, depending on if the derby being run has multiple heats and feature, or just a single heat, as well as the types of vehicles being demolished (compact car derbies tend to be finished much more quickly than school bus derbies, for example). Normal heats can last anywhere from 10–30 minutes, while an entire event can take place over the span of a few days.<ref name="LATimes07212001" />

The last running car that makes contact with another driver wins the event.<ref name="LATimes07212001" /> In addition to a winner, most derbies also award a "Best in Show" or "Mad Dog" award to the participant who puts on the most exciting or spectacular performance without winning the derby; this is usually decided by [[voice vote]] of the audience. (This is especially true in multiple-heat contests, where the addition of best-in-show provides more contestants for the feature event.)