Modern drag races are started electronically by a system known as a Christmas tree. A common Christmas tree consists of a column of seven lights for each driver or lane, as well as a set of light beams across the track itself.
Each side of the column of lights is the same; from the top down, there is one blue LED light set arranged in a circle with a white line through the center, then three amber bulbs, then a green bulb and a red bulb. When drivers are preparing to race, they first cross the beams 7 Drag strip stageing lights behind the starting line.
Crossing this beam activates the top half of the circle. Once pre-staged, drivers roll up 7 inches and cross the second beam on the starting line, bottom half of the circle, including the crossing line.
Once both drivers have crossed the staged sensor, an official starter or automatic starting system will activate the next lighting sequence. After this point, the lighting sequence will be different based on the type of tree and start that a race is using.
The "Standard" tree will light up each large amber light consecutively with a. A "Professional" tree will light up all of the large amber lights simultaneously, and then after a.
Some classes will use a hybrid tree, known as a. On the activation of the green light from either style of tree, the drivers are supposed to start the race. Leaving the "Staged" line before the green light activates will instantly stop the count down and result in a lighting of the red light and a provisional disqualification of the offending driver in heads-up starts only.