What is a speed index?

WHAT IS A SPEED INDEX?
Information provided by Jerry Files of Files Barrel Horses. Information resource AQHA.

The S.I., or speed index, was developed by the AQHA as a scale to measure the speed of a horse. The AQHA set minimum standards for ratings.
Some racing surfaces are faster than others, and this was taken into consideration. The fastest 9 race times at each track at each distance are averaged each year. If the average exceeds the minimum AQHA requirements, the tracks requirements for a speed index will be increased. For example, the AQHA minimum for a 100 S.I. at 220 yards is 11.95 seconds at Delta Downs in Louisiana. The track surface is deep there and times are slow so they maintain the minimum. Sam Houston Park in Texas has a fast surface. 11.83 seconds is required for a 100 S.I. due to faster overall times.
Minimum times are set at each approved distance. An S.I. varies according to distance. At 220 yards .022 equals one speed index point. If 11.950 is a 100 S.I., 11.972 would be a 99 S.I. rating. Conversely, 11.928 would be an 101 S.I. rating.
The speed rankings of A, AA, AAA, and AAAT are derived from these numbers.
An S.I. of 70-79 is A, 80-89 is AA, 90-99 is AAA, and 100+ is AAAT.

Below is a chart of minimum time requirements:

OFFICIAL DISTANCE (In Yards)	MINIMUM STANDARD TIME ( for 100 Speed Index Rating)	SPEED INDEX POINT
220 straightaway	11.95	.022
250 straightaway	13.35	.025
300 straightaway	15.55	.03
330 straightaway	16.95	.033
350 straightaway	17.85	.035
400 straightaway	20.15	.04
440 straightaway	22.05	.044
550 straightaway	27.70	.055
660 straightaway	33.50	.066
660 around one turn	34.60	.066
770 around one turn	40.36	.077
870 around one turn	45.60	.087

A special thank you to Jerry & Sandi Files for compiling this information. Be sure to check out their site, Click Here.