How the NHRA Christmas Tree Works and What the Colors Mean

The Christmas Tree that everyone is talking about at a drag race isn’t the fancy evergreen we display in our living rooms during the holidays. But it does have flashing blue, amber, green, and red lights.

It’s the electronic starting device that uses calibrated LED lights that produce a visual countdown for each pro driver in an NHRA pairing.

The process starts with the blue light at the top of the apparatus. The blue light is actually two lights, two half-moons. The blue lights made their debut before the 2011 spring race at Charlotte, N.C. Both the top and bottom half of the blue lights interact with two light beams that cross the starting-line area and are connected to trackside photocells that are wired to the tree and electronic timers in the control tower.

Blue Lights

The top half-moon blue light is the pre-stage indicator. When the front tires of a race car break the first of those two light beams, the top half of the blue light comes on. That means the racer is about seven inches from the starting line, approaching the starting line and the “staged” position. When the racer rolls the car into the stage beam, the front tires are exactly on the starting line and lights the bottom half of the blue light. That indicates the vehicle is ready to race. The auto-start system limits the time to seven seconds that a driver can stage once the opponent has lit both pre-stage and stage beams.

A move that smacks of game-playing or unsportsmanlike conduct—but often is simply a mistake by a later-apologetic and chagrined driver—is what’s known as “double-bulbing.” It happens when a drive rolls the car deep into the staging area and lights both staging bulbs on the Christmas Tree at the same time. It gives the opponent almost no time to get set to launch and disrupts that driver’s routine.

If racers want to play psychological games with each other to interrupt his/her sequence or maybe even get the crowd riled up for some added drama, he/she could engage in what’s called a burndown. That’s the situation in which both drivers intentionally hesitate to move into the staging position. Sometimes it pays off. Sometimes it backfires. Sometimes it perturbs the official starter, who orders both to shut off their engines and make way for the next pairing.

When both vehicles are fully staged, the starter will activate the Tree, and each racer will focus on the three large amber lights that correspond to the driver’s lane.

Amber Lights

Amber lights are the next to light up. All three amber lights will flash simultaneously, followed four-tenths of a second later by the green light (a Pro Tree), or the three bulbs will flash consecutively five-tenths of a second apart, followed five-tenths later by the green light (a Sportsman Class Tree). The NHRA began using LED amber lights on the Christmas Tree before the 2003 season. They replaced the incandescent lights, because the massive vibrations from the 11,000-horsepower Top Fuel dragsters and Funny Cars burned out the bulbs too easily.

Green Lights

The green light means “Action!” Once the green light flashes, the driver is free to take off, although racers will say if one waits for green, he’s late. Drivers hope for a green-light start, because that means he hasn’t disqualified himself by leaving the line too early. That infraction is indicated by a red light.

Red Lights

The red light will flash in a fouled-out driver’s lane when the car leaves the starting line too early or in some cases is staged too deep in the beams.

A perfect reaction time is .000 seconds.

The system records each driver’s elapsed time and speed for each run. As soon as a car leaves the staging beams, it activates an E.T. clock, which stops when the vehicle reaches the finish line. The start-to-finish clocking is the elapsed time. Incremental times and speeds are recorded at intervals along the course: at the 60-, 330-, 660-, 1,000-, and quarter-mile marks. For Top Fuel and Funny Car racers, the finish line is at 1,000 feet. For all other NHRA classes, pro and sportsman alike, the quarter-mile marks the finish line. Winners are determined by elapsed time.

Since 1984, the NHRA officially uses CompuLink timing systems at venues on the professional drag- racing circuit (including the Christmas Tree, control units, timing sensors, cables, program software and time-slip printer).

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