Drag racing
Drag racing is a type of motor racing in which automobiles or motorcycles (usually specially prepared for the purpose) compete, usually two at a time, to be first to cross a set finish line. The race follows a short, straight course from a standing start over a measured distance, most commonly ¼ mile (1,320 ft (402 m)), with a shorter 3/16 mile 10 feet (1,000 ft (305 m)) becoming increasingly popular, as it has become the standard for nitromethane-powered Top Fuel dragsters and funny cars where some major bracket races and other sanctioning bodies have adopted it as the standard, while 660 ft (201 m) (1/8 mi) is also popular in some circles. Electronic timing and speed sensing systems have been used to record race results since the 1960s.
The history of automobiles and motorcycles being used for drag racing is nearly as long as the history of motorized vehicles themselves, and has taken the form of both illegal street racing, and as an organized and regulated motorsport. This article covers the legal sport.
Before each race (commonly known as a pass), each driver is allowed to perform a burnout, which heats the driving tires and lays rubber down at the beginning of the track, improving traction. Each driver then lines up (or stages) at the starting line.
Modern professional races are started electronically by a system known as a Christmas tree, which consists of a column of lights for each driver/lane, and two light beam sensors per lane on the track at the starting line. Current NHRA trees, for example, feature one blue light (split into halves), then three amber, one green, and one red. When the first light beam is broken by a vehicle's front tire(s), the vehicle is "pre-staged" (approximately 7 inches (180 mm) from the starting line), and the pre-stage indicator on the tree is lit. When the second light beam is broken, the vehicle is "staged", and the stage indicator on the tree is lit. Vehicles may then leave the pre-stage beam, but must remain in the stage beam until the race starts.
Once one competitor is staged, their opponent has a set amount of time to stage or they will be instantly disqualified, indicated by a red light on the tree. Otherwise, once both drivers are staged, the system chooses a short delay at random (to prevent a driver being able to anticipate the start), then starts the race. The light sequence at this point varies slightly. For example, in NHRA Professional classes, three amber lights on the tree flash simultaneously, followed 0.4 seconds later by a green light (this is also known as a "pro tree"). In NHRA Sportsman classes, the amber lights illuminate in sequence from top to bottom, 0.5 seconds apart, followed 0.5 seconds later by the green light (this is also known as a "sportsman tree" or "full tree"). If a vehicle leaves the start line before the green light illuminates, the red light for that lane illuminates instead, and the driver is disqualified (also known as redlighting). In a handicap start, the green light automatically lights up for the first driver, and the red light is only lit in the proper lane after both cars have launched if one driver leaves early, or if both drivers left early, the driver whose reaction time is worse (if one lane has a -.015 and the other lane has a -.022, the lane of the driver who committed a 0.022 is given the red light after both cars have left)., as a red light infraction is only assessed to the driver with the worse infraction, if both drivers leave early. Even if both drivers leave early, the green light is automatically lit for the driver that left last, and they still may win the pass (as in the 2014 NHRA Auto Club Finals Pro stock class, Erica Enders-Stevens and Jason Line both committed red light infractions; only Line was assessed with a red light, as he was -.011 versus Enders-Stevens' -.002).
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