What type of vehicle is least likely considered a "covered auto" in a personal auto policy?

A commercial tractor-trailer combination is least likely considered a "covered auto" in a personal auto policy because personal auto policies are specifically designed to provide coverage for personal vehicles, such as cars and light trucks, that are primarily used for personal, non-business purposes.

Commercial vehicles, including heavy trucks and trailers used for business purposes, require a different type of insurance policy that is tailored to address the unique risks associated with commercial transportation. Personal auto policies typically do not extend coverage to vehicles that are intended for business or commercial use, which is why a commercial tractor-trailer combination falls outside the scope of what would be covered under a standard personal auto policy.

In contrast, newly acquired passenger autos, temporary substitute passenger autos, and owned private trailers are all categories that personal auto policies typically cover, given that they are used in the context of personal use rather than commercial activities.