A drag race is an acceleration contest, on a track, or dragstrip, that begins from a standing start between two vehicles over a measured distance. The losing racer in each contest is eliminated, and the winning racers progress until one remains. These contests are started by means of an electronic device commonly called a Christmas Tree because of its multicolored starting lights. On each side of
the Tree are seven lights: two small amber lights at the top of the fixture, followed in descending order by three larger LED lights, a green bulb, and a red bulb. Two light beams cross the starting-line area and connect to trackside photocells, which are wired to the Christmas Tree and electronic timers in the control tower. When the front tires of a vehicle break the first light beam, called the pre-stage beam, the pre-stage light on the Christmas Tree indicates that the racer is approximately seven inches from the starting line. When the racer rolls forward into the stage beam, the front tires are positioned exactly on the starting line and the stage bulb is lit on the Tree, which indicates that the vehicle is ready to race. When both vehicles are fully staged, the starter will activate the Tree, and each racer will focus on the three large amber lights on his or her side of the Tree. Depending on the type of racing, all three large amber lights will flash simultaneously, followed four-tenths of a second later by the green light (called a Pro Tree), or the three bulbs will flash consecutively five-tenths of a second apart, followed five-tenths later by the green light (called a Sportsman, or full, Tree). Two separate performances are monitored for each run: elapsed time and speed. Upon leaving the staging beams, each vehicle activates an elapsed-time clock, which is stopped when that vehicle reaches the finish line. The start-to-finish clocking is the vehicle's elapsed time (e.t.), which serves to measure performance. Speed is measured in a 66-foot "speed trap" that ends at the finish line. Each lane is timed independently. The first vehicle across the finish line wins, unless, in applicable categories, it runs quicker than its dial-in or index (see glossary). A racer also may be disqualified for leaving the starting line too soon, leaving the lane boundary (either by crossing the centerline, touching the guardwall or guardrail, or striking a track fixture such as the photocells), failing to stage, or failing a post-run inspection (in NHRA class racing, vehicles usually are weighed and their fuel checked after each run, and a complete engine teardown is done after an event victory). Handicap Racing
NHRA uses a handicap starting system to equalize competition in certain categories. In essence, this system enables vehicles of varying performance potentials to compete on an equal basis. The anticipated elapsed times for each vehicle are compared, and the slower of the two cars is given a handicap head start equal to the difference of the two e.t.s. By using this system, virtually any two vehicles can be paired in a competitive drag race. At NHRA national events, a handicap system is used in Competition eliminator, where the handicap is determined by national indexes, and Super Stock and Stock, where drivers are allowed to "dial-under" the national index, or select an elapsed time quicker than the national index. A driver selects an e.t., or "dial-under," that he or she thinks the car will run. Here's how it works. If car A chooses a dial of 16.00 and car B chooses a dial of 14.50, car A will get a 1.5-second head start. If both vehicles cover the quarter-mile in exactly the predetermined elapsed time, the win will go to the driver with the best reaction time, or whoever reacts quickest to the green "go" signal on the Christmas Tree. If a driver runs quicker than his or her dial, he or she is said to break out and is disqualified. If both drivers run quicker than their dials, the win goes to the driver who breaks out by the least. A foul start, or red-light, takes precedent over a breakout, so a driver who red-lights is automatically disqualified even if his or her opponent breaks out.
