Under what circumstance can two insurance policies apply for the same auto?

The scenario where two insurance policies can apply for the same auto is when the auto is owned and insured by someone else. This situation typically arises when a person borrows a vehicle from a friend or family member who has their own insurance policy. In this case, the owner's insurance would provide coverage for the vehicle, while the borrower may also have their own insurance policy that could extend to cover them while driving the borrowed car.

This principle is based on the concept of "additional insured" status and coverage provisions that many policies have in place to ensure some level of protection exists when a vehicle is being operated by someone other than the owner. Other options do not align with the conditions under which multiple policies would serve to provide coverage for the same vehicle. For instance, if the operator's insurance is primary, it means that this individual’s policy will pay first, not necessarily allowing for dual coverage. Similarly, if the auto is rented under an insured's name or primarily used by a resident of the household, this does not inherently create a situation where two different policies apply at the same time for the same vehicle under standard insurance rules.