Most DWIs involve the operation of a car, but DWI arrests are not specifically limited to only driving a car.
All over the U.S., courts have sentenced people to jail time, community service, or both for DWIs not involving an automobile. Section 20-138.1 of the North Carolina General Statutes defines "impaired driving" as driving any vehicle upon any vehicular area in the state. Nowhere in this statute explicitly states that it has to be a car.
Let’s take a look into Section 20-4.01(49) of the general statutes. This part of the statute defines the term "vehicle" as anything that can be used to transport people along roads. The only exceptions to this term are fixed-track vehicles (e.g. trains) and mobility devices (e.g. wheelchairs).
Regardless of how the vehicle is primarily used, the driver can still be charged with DWI under these circumstances. A tractor may not be designed to buzz along the Interstate, but it still carries the driver to places. At one time, you could also be charged with DWI on horseback, as it was with State v. Dellinger, but subsequent amendments have removed horses and we are not aware of any group like MADHR (Mothers Against Drunk Horseback Riding).
However, this is just scratching the surface. It's not easy determining what vehicle meets the requirements for the legal definition of a "vehicle." For instance, you can't be charged with DWI on a vehicle "moved solely by human power" (Lewis v. Watson, 1948), but perhaps bicycles are within the scope of the law. When in doubt, call a cab instead.