A motor vehicle liability policy, as said term is used in sections 60-501 to 60-569, shall mean an owner's or an operator's policy of liability insurance, certified as provided in sections 60-529 to 60-531 as proof of financial responsibility, and issued, except as otherwise provided in section 60-531 by an insurance carrier duly authorized to transact business in this state, to or for the benefit of the person named therein as insured.