mass production. The naming apparently came from the use of small glass Christmas tree lights David used for his miniature prototype. Regardless of the actual inventor(s), the Christmas Tree and timing system is a marvel in drag racing history. Tree changes The Christmas Tree has changed three times since its original debut in 1963 for the U.S. Nationals at Indianapolis Raceway Park. The original Tree had five amber lights, but no pre-stage or stage bulbs. A pair of small amber bulbs, originally located at the start line, known as the pre-stage and stage bulbs, were added in 1964 Winternationals, held at the Los Angeles Fairplex (which still conducts the races today). Each of the five yellow lights were lit consecutively at a .500 delay before the light turned green. For the 1971 season, the Professional Tree was instituted; only the fifth of five yellow bulbs (the last) was lit, followed by four-tenths of a second later, the green light, for professional classes. As the Pro Stock class was having issues with hood scoops and the visibility of the only amber light being lit (bottom) before the green light, the NHRA, as part of Christmas Tree changes in 1986, instituted the first major overhaul of the Tree; two amber lights were removed on each side, making the tree three amber lights before green. The NHRA said they could save around four minutes with the reduction of starts by one second in sportsman classes. The second change was made in the Professional tree configuration. All three amber lights turn on together before the tree turns green. NHRA introduced another significant change to the Tree, switching to LEDs instead of incandescent bulbs, at Pomona in 2003. This saved changing as many as twenty bulbs at a meet due to filaments being broken by the vibration from exhausts of Top Fuel cars. It also led to a drop in reaction times. Prior to the 2009 season, the starter activated the tree. The NHRA and drivers discovered drivers were aware when the NHRA official would trigger the switch after both cars were staged, so code was written to create a random delay between the second car staged and the lights starting in order to prevent drivers from "guessing" the tree activation. Prior to the 2011 Charlotte spring race, the small amber bulbs were replaced with the current blue bulb. For the Charlotte and starting in