The short answer to this question is that sometimes it is possible to get a citation for driving under the influence (DUI) on a horse or a bicycle. This varies widely from state to state, however, depending on local laws and how a state defines a “vehicle.” As a general rule, it is better to be safe, rather than sorry, and people should avoid riding or cycling if they have been consuming alcohol. Depending on regional laws, a DUI on a horse or bicycle can result in hefty fines and the loss of a driver's license.

DUI laws always apply to all motor vehicles, such as cars, motorcycles, and scooters. In some states, someone who gets a DUI on a horse can challenge it, arguing that a horse is not a motor vehicle. If the definition of a “vehicle” is sufficiently ambiguous, the court may not uphold the challenge, but if a “vehicle” is specifically something with a motor, a DUI on a horse will be thrown out of court. The same goes for a bicycle, since a bicycle lacks a motor.

However, a state or region may choose to create laws specifically targeting drunk riders and cyclists. In this case, it is entirely possible to get a DUI on a horse, although the punishments may be slightly different than those in a motor vehicle. In a region where a citing officer knows that someone cannot get a DUI on a horse or bicycle, another type of citation may be issued. For example, a drunk cyclist may be charged with reckless conduct, public intoxication, or disturbing the peace.

While the idea of a DUI on a horse may seem ludicrous, the main concern from a law enforcement point of view is public safety. Someone riding a horse or bicycle while intoxicated could potentially be a risk to others. Drivers, for example, might get in an accident because of the erratic riding pattern of the drunk individual. In the case of a horse, animal endangerment is also an issue. Several states have documented cases in which a horse died or was severely injured as a result of an intoxicated rider.

The procedure for citing and punishing a DUI on a horse is usually the same for that in a motor vehicle. A law enforcement officer stops the rider or cyclist because the officer suspects that the rider may be under the influence. If a test such as a breathalyser indicates that the rider is intoxicated, the officer will issue a citation for a DUI on a horse. In many states, the lawbreaker's license will be immediately revoked, and he or she will have to go to court to get it back. While in court, fines may be imposed, along with public service.