The answer is a resounding Yes!, they are enormously useful.

The horse training expert referred to is named Jesse Beery. Beery was a world famous horse trainer from late 1800's who possessed amazing ability with horses.

Fortunately, Beery's secrets remain after all these years. His information can be found in his book he wrote in late 1800's. However, very few copies of his book exist. It is virtually impossible to find an original - much less one that is readable.

Here is a partial reading from first chapter of Beery's book:

Fear is principal motive which causes colt to resist training. It is natural for him to kick against an unknown object at his heels, to pull his head out of halter as from a trap, and if of a bad disposition, to strike and bite if he does not thoroughly understand you.

He learned to train horses at a very young age. It was clear he had a gift for horse training and made it his life's work.

Among almost countless things Beery could do with a horse, he taught them tricks. One of most amazing tricks he taught was teaching a horse to drive without lines. (In layman's terms, you have no long reins (known as lines) connected to horse. The only connection to horse is buggy hitched to horse) This trick almost defies belief!

Beery said this about driving a horse without lines: "While I do not advocate it as being a universally practical way of driving a horse, yet it is possible to so thoroughly train horse to certain signals that he can be controlled more reliably under excitement and in case of danger than it would be possible to manage him with bridle and lines."

Beery says there are a number of ways to teach this to a horse but suggests his method as most reliable.

In a nutshell, Beery first turned his horse loose in an enclosure about twenty-five feet square. He would walk in with a whip and teach horse to have confidence in him and not fear whip. (The horse is never whipped).

Once horse has learned to come to handler at command of "Come Here" and shows no fear of whip while it's gently waved over his head and body, and will follow handler all about ring, then you have laid a good foundation for further instruction.

Put horse away until next day where horse learns signals of whip.