A Matter of Time – Drag Racing Elapsed and Reaction Times Explained in this year

Perhaps among the most taken for granted piece of the drag strip is something intangible, always fleeting, and something we drag racers try to keep to an absolute minimum: time. Time is a drag racers best friend and enemy. A split-second is close to an eternity as races are frequently won and lost by mere ten-thousandths of a second.

Methods for generating lap-times have evolved over the course of organized drag racing’s 60-year life. Perhaps the most ground breaking innovation in timing advancements came from early drag racing organizer C.J. Hart in 1950. Hart fashioned a timing system comprised of two photo cells that would record a racers top speed. Long before the construction of elaborate, purpose built timing towers, Hart’s timing system was operated from an out of commission hearse stationed near the finish line. Just outside the hearse, Hart would post on a score board the top speeds of the meet and the names of those fast drivers. The introduction of this timing system actually preceded the formal establishment of quarter mile racing, as meets at the time were generally contested at roughly three-tenths of a mile.

Today, this technology translates into the bright orange cubes we see strategically placed between the two lanes over the distance of the quarter-mile. These “timing cones” are actually photo cells, similar to what C.J. Hart introduced in 1950. The timing system has become further sophisticated, now recording incremental times, total elapsed times, and average miles per hour. Times are now recorded at 60′, 330′, 660′ (1/8-mile, half track), 1,000′, and 1,320′(1/4-mile, finish line). Average mile per hour is also calculated at the 1/8-mile and ┬╝-mile marks on the drag strip.

A modern day, sophisticated timing system is capable of measuring ETs as precise as one-millionth (0.000001) of a second. However, all of the ultra fancy high-tech fiber-optic and digital technology in the world is useless if the driver can’t make sense of the data generated. Aside from the elapsed times determining the outcome of the race, the precise numbers found on your time slip are highly beneficial in helping improve your driving skills.

There is no better place to begin this discussion than the starting line. A common misconception of newcomers is that the ET (elapsed time) clock begins when the green starting line bulb is lit. This is a false misunderstanding. In fact, there are two separate time recordings taken on the race track: reaction time and elapse time. The reaction time is the time elapsed from the flash of the green bulb to the motion of the vehicle as it completely leaves the starting line beam. If that seemed a bit too much, let me refresh your memory and elaborate further.

Recall, timing sensors are triggered by the disruption of a photocell. Lining the drag strip at strategic locations are photocells that project an invisible beam that contacts a reflector (the orange cube) on the center line. The disturbed beam triggers the timing system. The stage light (second set of yellow incandescent bulbs just above the first amber LED bulb) on the Christmas tree tells the starter and fellow competitor that you are prepared and committed to running the race. The stage light is activated by the starting line beam. The time that passes between the green bulb lighting and the front tire of the race car exiting the stage beam accounts for the driver’s reaction time. A perfect reaction on a typical five-tenths (0.500) of a second full-tree (three amber bulbs countdown sequentially in half (0.500) second intervals) is 0.500 seconds, or more simply converted today as 0.000 seconds.

The Christmas tree has had a number of facelifts during its nearly 50-year long stint as the standard method of starting competition drag races. Throughout the 1950s and early 1960s, a flagman standing between the two race cars would signal when the drivers were to launch off the starting line. The obvious dangers and subjectivity of using a flagman contributed to design and implementation of the Christmas tree. The Christmas tree made its formal debut at the 1963 NHRA Nationals. The Christmas tree originally consisted of five-amber bulbs but was reduced to it’s now standard three-amber bulbs in the mid-1980s. In 2003, the NHRA introduced LED bulbs, replacing the once standard incandescent amber bulbs.

Two basic Christmas tree designations exist: pro tree and full tree.

The pro tree is used primarily in heads-up categories (Top Fuel, Funny Car, Pro Stock, Pro Modified, Pro Stock Bike, Top Alcohol Dragster and Funny Car, and Super Comp/Gas/Street). With the pro tree, all three-amber lights illuminated instantly.

The full tree is primarily used for bracket-style dial-in races, when a staggered tree is necessary to accommodate vehicles of sometimes vastly different ETs. Such categories using a full tree include Competition Eliminator, Super Stock, Stock Eliminator, Super Pro, Pro, Sportsman, and Junior Dragster. With the full tree, each amber bulb illuminates sequentially, typically 0.500-seconds.

Yes, there are exceptions to these general rules of thumb. For instance, the majority of pro tree races are contested on a 0.400-second tree, where 0.400-seconds separate the yellow amber bulbs and the green bulb. The Super Street (10.90 heads-up) category, however, is an exception as they use a 0.500-second tree.

Regardless of 0.400- or 0.500-second trees, the driver’s time slip will read perfect as a standardized 0.000-second. To demonstrate, what was once a 0.500-second perfect reaction time would now be a 0.000-second perfect reaction time. The same goes for 0.400-second perfect reaction times. Thus, any deviation from a perfect 0.000-second reaction time will be recorded as a -/+ 0.000-second.