OK, so you have decided to finally find out just how your car really performs, and you have taken it to your local drag strip. You've met new friends in the pits, you've experienced the adrenaline of staging, and your car gave everything it had to get you to the white line as fast as possible. And now you have a slip of paper in your hand filled with numbers and measurements... what do they mean?
 A typical Accutime(tm) timeslip
The time slip you see at the left is from an Accutime system, a common system used by many strips. There are variations depending on the version of software that is being used, and some strips may use other systems entirely, but the basic data will remain the same, so you should be able to use this image and this text as a reasonable guide.
For the most part we are going to disregard everything above where it says "Left" and "Right". That is mostly data about which track the slip was produced at, the date, what kind of event it was (in this case a Test and Tune which is an informal event without dial-ins, more about that later) and other miscellaneous data.
Below that you will see three columns of data, the first representing what happened on the left track, the center denoting the specific data being presented, and the right representing what happened on the right track. You'll notice that the left and right racers are given specific numbers, in that case 129 and 120. These numbers are usually given to you by the track's technical/safety inspector.
Below that is the "Dial in" category. In test and tunes and other "Heads Up" style racing this is an unused category; it is used to set up a handicapping system during bracket racing. For purposes of this article it can be ignored.
Reaction Time
Now we get to the first very important category: Reaction time. What this category shows is the amount of elapsed time between lighting of the green light and your car leaving the starting line. How to read this number depends entirely on the lighting system being used by your track. Tracks that have incandescent (old school) style tree lights use a baseline of .500, while other tracks use LED style tree lights and use a baseline of .000. This particular track uses incandescent lights, so the number we need to keep in mind is .500. Anything above that time represtents how many tenths, hundreths and thousanths of a second after the lighting of the green light it took for each car to leave the starting line. Obviously the closer you are to .500 the better and there are many many races won or lost at the starting line. Keep in mind that by the time you reach the end of the track, each tenth of a second can represent an entire car length or more, so you could have a faster car, leave 3/10ths of second slower than your opponent and still lose. The left car in this example had a reaction time of .8024 (it's hard to read) and the right was .9247. In reality both of those times are considered pretty slow, but the first time at the track you can expect to be several tenths of a second off the green.
In this example that means that the left car's actual reaction time was .3024 since that is how far off of .500 his launch was. The right car's reaction time was .4247. Nearly half a second sitting on the line after the light went green! By the end of the track that could easily translate into 75 feet or more of distance.
Leaving before the light goes green will garner you either a negative reaction time in the case of LED lights, or something below .500 with incandesent. Usually this will be indicated by "Red light" being printed somewhere in your column and always indicates a forfeit of the race.
An important note here: reaction time does NOT affect any of the elapsed times that you are going to see from here on down, with the exception of winner declaration and the finish margin. What that means is that if you cut a .900 reaction time and a 1/4 mile time of 15.00, that does not mean that if you were to cut a .500 reaction time that you would get a 14.60 1/4 mile time. The elapsed time timer does not start until your wheels leave the starting line, that means that you could in theory sit at the green light for two minutes and then turn in a 14 second run. This also means that one car may complete the 1/4 mile in less time than his opponent, and still lose the race.
From here on in we will concentrate on the right lane, car number 120.
60 Foot
Next after that is the 60 foot time. This is the time it took for car 120's front wheels to reach a point 60 feet from the starting line. This is considered a critical time by most racers, with a general concensus that 2 seconds flat is a very good time. The time shown on the slip is 2.4023, about 4 tenths of a second slower than that magic 2 second mark.
330 and 1/8 mile
These times represent the time, once again, that it takes the front tires of car 120 to trip the sensors that are both 330 feet and 1/8 of a mile from the starting line. We can extrapolate some data from this when compared to the car in the left lane. At the 60 foot mark the right car covered that distance 2/10s of a second faster than the left lane car. At the 330 foot mark that is down to 1/10 of a second, and at the 1/8 mile mark it is closer to 5/100 of a second. Below this we can see why: at the 1/8 mile, car 120 is going 78.37 mph while car 129 is going 75.49 mph. We can assume that either car 120 bogged badly on his takeoff or he is very highly geared. Since car 120 was 1/10th of a second slower on his take off, we know that if we were watching this race then right at the 1/8th mile mark the right side car was about 5/100 of a second behind the left side car and gaining fast.
1000 foot and 1/4 mile
As you might suspect again there are sensors at the 1000 foot mark and the 1/4 mile mark, and what they are looking for is the front tire of car 120. There is also associated MPH data. Car 120 finishes the race with a 14.40 and a speed of 99.69 mph.
Finish Margin
The data between Reaction Time and Finish Margin are not related to how the cars are performing against each other, rather they are indications of how each individual car was doing as it ran down the track. Finally here at the end we see who won and by how much: Car 120, by 3/10ths of a second, or roughly 3 car lengths. Below that you can see that indeed car 120 was confirmed as the winner.
All in all time slips give you critical pieces of information that you can use to determine how well both you and your car are perfoming. As you can see it is possible to lose a race at the stoplight, and that just because one car is faster at the take off, the race can be very different by the time you cross the finish line. And just as importantly it gives you absolute, hard facts. Car 120 beat car 129. You can't say that one side or the other was taken by surprise, or that one guy didn't realize that he was racing, or that one guy won because the other let off. It's hard data, on paper, for anyone to see.
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