What Is a Speed Index?

From the Quarter Racing Journal

Speed figures make the world go around – at least the world of American Quarter Horse racing. The speed index has been around since 1970, when it replaced the original letter-grade system, under which AAAT (read: Top triple-A) represented the top speed category and was followed by AAA, AA, A, B, C and D. The speed index system replaced the letter-based system with a number system. Originally, a 100 SI was roughly equivalent to the old AAAT.

The actual calculation of the speed index starts with taking the three fastest winning times at a particular distance for the past three years at a given track. These times are averaged together, and that averaged time is then the 100 SI for that distance at that track. If that average doesn’t meet the minimum standard time given by AQHA for that distance, then a minimum standard time is used.

To calculate an SI, the time the horse recorded is compared to the average speed for the distance of the race, and points are added or subtracted based on whether the time was faster or slower than the average. The number of points subtracted or added varies according to the distance of the race, and is based on a chart distributed annually by AQHA.

Speed Indexes vs. Speed Ratings

For more than 20 years, Quarter Horse handicappers have had two speed figures to choose from: the traditional speed index and the TrackMaster speed rating.

In 1997, TrackMaster, a wholly-owned subsidiary of Equibase Company LLC, introduced a new speed figure to fans of the sprint game. Valuable to handicappers, breeders and buyers, TrackMaster’s ratings standardize horses’ finishing times across all different tracks, distances, surfaces and weather conditions. The numbers are generally between 0 and 130, with 130 being an extremely high figure earned by a Grade 1-caliber horse.