Any negligence or wilful misconduct of a minor when driving a motor vehicle upon a highway must be imputed to the person who has signed the application of such minor for a beginner’s permit, instruction permit, or driver’s license, which person is jointly and severally liable with such minor for any damage caused by such negligence or wilful misconduct, except that if such minor is protected by a policy of liability insurance in the form and in the amounts as required under Chapter 9 of this title and §§ 38-77-140 through 38-77-310, then such parent or guardian or other responsible adult is not subject to the liability otherwise imposed under this section.