Horse Cases, the Cheapest Cost Avoider Rule, and Liability for Highly Autonomous Vehicle Accidents

• Citation: Vol. 4 No. 1
• Publication year: 2021

Daniel Barabander^*

The author of this article applies the cheapest cost avoidance liability regime to highly autonomous vehicle accident scenarios to determine the likely liability for manufacturers of this new technology.

Courts have created a liability regime in horse accident cases that assigns fault to the cheapest cost avoider. Courts determine the cheapest cost avoider by looking to the horse owner and rider's access to knowledge and level of control relevant to avoiding accidents. When applied to highly autonomous vehicles ("HAVs"), vehicles with autonomy Level 4 or Level 5, the cheapest cost avoider will almost always be the manufacturer.¹

This article proceeds as follows. First, it shows why the analogy of horses to HAVs is a reasonable one. Second, it analyzes horse accident cases, beginning with cases involving asymmetrical access to knowledge that could be used to avoid an accident between the horse owner and rider. Then it argues that these cases demonstrate how access to knowledge relevant to avoid an accident changes who is the cheapest cost avoider, and thus, who the courts hold liable. It then discusses a category of cases where access to this knowledge between the parties is equal, but the parties could have exerted control to avoid an accident. Next, it argues that these cases show how the level of control to avoid an accident changes who is the cheapest cost avoider, and thus, who the courts hold liable.

The cheapest cost avoidance liability regime is then applied to HAVs. The article next argues that HAV manufacturers will have increased access to knowledge and control to avoid accidents in almost all situations when compared to the passenger and will, therefore, almost always be the cheapest cost avoider. This result suggests the manufacturer will almost always be liable, which is

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a different outcome to horse accident cases, where liability shifts between horse owner and rider.

The Analogy of Horses to HAVs

Why are horses a reasonable analogy to HAVs? First, and most obviously, HAVs and horses are both used by humans as a means of transportation. Second, HAVs and horses are both "devoted to the service of mankind."² Third, HAVs and horses both act autonomously; they make transportation decisions independent of any human occupant.³ Fourth, these autonomous decisions can lead to accidents that reasonable human operators would not make.⁴

There are certainly good arguments that the analogy between HAVs and horses does not work.⁵ However, the focus of this article is not to determine whether or not the analogy is apt, but rather, to see how the cheapest cost avoidance liability regime used in horse accident cases would apply to HAV accidents assuming the analogy is reasonable.

The Structure of Horse Accident Cases

Definition of "Horse Accidents"

In this article, "horse accidents" are accidents caused, at least in part, by the decision-making of a horse that its owner rented or sold to a rider that was subsequently injured.⁶ These cases are the focus because a horse owner selling or renting a horse is analogous to an HAV manufacturer selling or "renting out" their vehicles as part of a ride-hailing service.⁷

Factors for Establishing Fault in Horse Accident Cases

Regardless of whether the injured rider brings a suit in contract⁸ or tort,⁹ for her to recover, "the required proof is the same": (1) that the horse at issue was, in fact, unsuitable and the injury resulted from this unsuitability, and (2) the owner knew about this unsuitability or should have reasonably known.¹⁰ The owner can raise two defenses of rider fault to free her from liability: (1) that the injuries were the "result of [the rider's] own fault or neglect in

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the management of the horse," and (2) that the rider assumed the risk of a dangerous activity.¹¹

In establishing these factors, the courts look to a variety of evidence, including actions and statements by the owner,¹² the length of time the owner was in possession of the horse,¹³ and any past incidents¹⁴ involving the horse that displayed its dangerous tendencies.¹⁵

Courts Assign Fault Based on Who Is the Cheapest Cost Avoider in Horse Accident Cases

The way courts assign fault in horse accident suits is a case-by-case assessment of which actor, between the horse owner and the rider, was the cheapest cost avoider. The cheapest cost avoider is the actor who can most efficiently take precautions to avoid the harm that occurred.¹⁶ Courts assign the cheapest cost avoider in two scenarios: (1) when the rider and owner have asymmetrical access to knowledge relevant to avoid the accident, and (2) when the parties have equal access to this knowledge. In the former, access to information determines the cheapest cost avoider, and in the latter, it is determined by level of control.

When There Is Asymmetrical Access to Knowledge Relevant to Avoid the Accident Between the Parties, Courts Assign Fault to the Party with Easier Access to This Knowledge

The Rider Has Easier Access to Knowledge Relevant to Avoid the Accident When the Rider Has Previously Experienced the Dangerous Tendencies of the Horse That Caused It

In Hale v. O'Neill, a rider was injured when a horse "bolt[ed] and swerved."¹⁷ The rider had previously ridden the horse six times, had experienced its "tendency to bolt and swerve," and knew that in those situations, it was "pretty hard" for him to control the horse.¹⁸ Even though the owner did not warn the rider about the horse's tendency to bolt and swerve, the owner was not liable because the rider was "fully aware of these dangerous tendencies" and knew of his inability to control these tendencies.¹⁹

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In McNish v. Gilbert, a rider got off a horse after it began to act erratically.²⁰ The rider then got back on the horse, at which point she was injured.²¹ The court stated that the "significance fades from materiality" as to whether or not the owner properly warned the rider that the horse was adequately trained or not because, by the rider experiencing the dangerous tendency, she became fully aware of it: on "the first occasion of the horse's behavior" the rider was "put on notice that the horse was not fully broken [trained]" and thus, she knew it would "manifest an intolerance to her riding."²²

Hale and McNish show us that when a rider has prior experience with a horse's dangerous tendencies, it will dramatically reduce her chances of recovery when an accident occurs due to these tendencies because the rider can most effectively and inexpensively avoid the accident. Although both the owner and rider have knowledge of the horse's dangerous tendencies, the rider has access to knowledge that the owner does not: how skilled the rider is at managing these dangerous tendencies. In Hale, the rider had experienced the horse's tendency to bolt and swerve and knew it was "pretty hard" for him to control the horse in those situations.²³ In McNish, the rider experienced the horse's tendency to buck before the buck that caused her accident and knew it "manifest[ed] an intolerance to her riding."²⁴

These riders, armed with both the understanding of the horses' tendencies and their own skill at managing them, inherently have more knowledge than the owners to avoid the accidents effectively.²⁵ An owner would need to do an in-depth interview of rider skill and see the rider's interaction with the horse to select a suitable horse for the rider. Meanwhile, a rider that has experienced the horse's tendencies can simply use the knowledge she already has about her ability to manage the horse's tendencies to know whether or not the combination will cause an accident. This asymmetrical access to knowledge that could prevent an accident makes the rider's ability to avoid the accident cheaper than the owner's, explaining why the courts hold the riders at fault in Hale and McNish, even though the owners did not warn the riders.²⁶

The Owner Has Easier Access to Knowledge Relevant to Avoid the Accident When the Rider Has Not Previously Experienced the Dangerous Tendencies of the Horse

In Conn v. Hunsberger, a rider was injured after a horse, "without any apparent cause, started to kick violently, and finally ran

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off."²⁷ The rider had never before ridden the horse that caused his accident.²⁸ The owner had recommended the horse to the rider as one that was safe.²⁹ The court cited testimony from experts that showed the horse "was not mild, kind, and gentle, but was wild and vicious."³⁰ A new trial was ordered in favor of the rider because the owner "did not exercise proper care in ascertaining the vicious nature of the animal."³¹ In reaching its conclusion, the court stated:

It is imposing no heavy burden upon the keeper of a livery stable to require him to investigate the character of the horses he keeps in his stable before hiring them to persons whose safety may be endangered by their vicious habits . . . [t]he customer is at his mercy, and must rely upon the liveryman to guard him against the danger of a vicious animal or defective vehicle.³²

In Harris v. Breezy Point Lodge, Inc., a rider was injured when she fell off a horse that reared.³³ The horse had reared before, causing a different rider to fall off.³⁴ The owner was held liable because there was evidence that he "had notice of certain tendencies that might make Duke [the horse] dangerous to an inexperienced rider and the jury could have found that such notice would have put a prudent man on guard."³⁵ Ultimately, the owner "was the proximate cause of . . . [the rider's] injuries" by not warning the rider of the dangerous tendencies of the horse.³⁶

In Hodge v. Montclair Riding Club, an experienced rider was injured after a horse reared, throwing her off.³⁷ The horse's tendency to rear was known by the owner but not the rider, as the horse had reared a month earlier with a different experienced rider, injuring him.³⁸ Handling a rearing horse without injury requires that the rider know how to...