Drag Racing Reaction Timing

Today there is talk about how to set your system for Reaction Time of the line when it comes to Drag Racing. This page will discuss the options for what is called a “Perfect Light” take off the line.

In drag racing there are 2 different ways that the starter can set the Christmas tree. One is called a ‘Sportsman’ tree, and the other is called a ‘Pro’ tree. The way the sportsman tree works is when the starter hits the button, it activates 3 separate amber’s prior to the green light. These amber lights have a half second interval between them, as well as a half second delay between the last amber light and the green light. A perfect light on a sportsman tree is a .500 light. What this means, is when the last amber comes on, there is a .500 second interval until the green light is activated. If you front tire broke the beam exactly when the green came on, it would be considered a perfect light, or a .500 light. If you left the beam 1/10th of a second after the green, it would be a .600 light. A good light for sportsman is typically a .520-.530 or better.
The way a pro tree works is once a car is staged (front tires in both the pre staged and staged beams), the starter hits the button. At that point all three amber lights light up at once, and then the green comes on. The interval between the 3 amber’s coming on and the green is .400 seconds, or 4/10ths of a second. -So a perfect light on a pro tree is a .400 . One big difference in these 2 different ‘trees’ is on a sportsman tree you are anticipating the green light, because you get to see 3 amber’s spaced 1/2 second apart prior to the green. So, you know when the green is coming as the 3 amber’s start to light up. On a pro tree, you are reacting to the flash of the 3 amber’s prior to the green light coming on. So, on a pro tree, you are having to react to the amber, but on a sportsman tree you have to anticipate the green from the 3 prior amber intervals.
So, on a sportsman tree you are trying to time your launch so the tires break the beam when the green light comes on, and the 3 half second intervals of the amber’s allow you to try to ‘time’ your launch. But on a pro tree you start to launch the car as soon as you see the amber’s flash, .4 seconds before the green comes.

First lets forget .500, For now and take a perfect reaction time is .0000 Anything quicker that a .0200 ( that is 2 hundredths of a second) light is considered good but can still get you eliminated.

Now a .500 light! If the system is set for a .500 as a perfect light, the old systems would now show a -.0200 for leaving 2 hundredths quicker, so they had a .500 light
so the time card would show a .480 red light. .0200 r/l. So anything below .500 would be a red light. New systems can be set for .000 or -.0200 will be the same as a .480

Example:

.508 is the same as .008

.520 is the same as .020

-.020 R/L is same as a .480 R/L