About

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)) used by nitromethane powered Top Fuel dragsters and funny cars along with some bracket races, 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.

Basics of drag racing

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.^[1] 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.^[2] 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).

Several measurements are taken for each race: reaction time, elapsed time, and speed. Reaction time is the period from the green light illuminating to the vehicle leaving the starting line. Elapsed time is the period from the vehicle leaving the starting line to crossing the finish line. Speed is measured through a speed trap covering the final 66 feet (20 m) to the finish line, indicating average speed of the vehicle during the run's last 66 feet (20m).

Except where a breakout rule is in place, the winner is the first vehicle to cross the finish line, and therefore the driver with the lowest combined reaction time and elapsed time. Because these times are measured separately, a driver with a slower elapsed time can actually win if that driver's advantage in reaction time exceeds the elapsed time difference. In heads-up racing, this is known as a holeshot win.^[3] 

In categories where a breakout rule is in effect (for example, NHRA Junior Dragster, Super Comp, Super Gas, Super Stock, and Stock classes, as well as some dial-in classes), if a competitor is faster than his or her predetermined time (a "breakout"), that competitor loses. If both competitors are faster than their predetermined times, the competitor who breaks out by less time wins. Regardless, a red light foul is worse than a breakout, except in Junior Dragster where exceeding the absolute limit is a cause for disqualification.

Most race events use a traditional bracket system, where the losing car and driver are eliminated from the event while the winner advances to the next round, until a champion is crowned. Events typically use 4, 8, or 16 car brackets. Drivers are typically seeded by elapsed times in qualifying. In bracket racing without a breakout (such as NHRA Competition Eliminator), pairings are based on times compared to their index (faster than index for class is better). In bracket racing with a breakout (Stock, Super Stock, but also the NHRA's Super classes), the closest to the index is favourable.

A popular alternative to the standard eliminations format is the Chicago Style format (also called the Three Round format in Australia), named for the US 30 Dragstrip in suburban Gary, Indiana where a midweek meet featured this format.^[4] All entered cars participate in one qualifying round, and then are paired for the elimination round. The two fastest times among winners from this round participate in the championship round. Depending on the organisation, the next two fastest times may play for third, then fifth, and so forth, in consolation rounds.^[5]

The standard distance of a drag race is 1320 feet, 402 m, or 1/4 mile. However, due to safety concerns, certain sanctioning bodies (notably the NHRA for its Top Fuel and Funny Car classes) have shortened races to 1000 feet. Some drag strips are even shorter and run 660 feet, 201 m, or 1/8 mile, but these are mostly lower level or grassroots racing.