Think about how long it takes to do an emergency stop in a car at 20 mph (
or 1/3 mile per minute which is 587 yards or almost six football fields). Then
at least double or triple that distance for stopping a horse at 20 mph.
Give me a break, haven't you ever seen a reining
horse or a roping horse stop at a sliding stop? Or better yet, ask Alice how
fast her 1000lb horse can stop when he spooks. The problem is when the rider
can't "control" their horse.
