Which of the following defines a motor vehicle according to insurance policies?

The definition of a motor vehicle in the context of insurance policies typically focuses on vehicles that are capable of being driven on their own, which aligns with the idea of being self-propelled. This means that a motor vehicle has an engine or motor that allows it to move independently without the need for external power sources, such as being towed.

In insurance terms, identifying self-propelled vehicles is crucial because these vehicles are generally eligible for coverage under various types of insurance policies, such as personal auto insurance and commercial vehicle insurance. Other types of vehicles, such as those that are non-motorized, trailers, or attachments, do not meet the criteria of being motor vehicles as per the typical definitions utilized in policy language and therefore are often excluded from standard motor vehicle insurance coverage. Similarly, commercial equipment is designated for operational purposes and usually does not fall under the realm of traditional motor vehicle definitions for insurance.

Thus, the focus on self-propelled vehicles captures the essence of what constitutes a motor vehicle, making it the correct answer in this context.