Section 113L. (1) No policy shall be issued or delivered in the commonwealth with respect to a motor vehicle, trailer or semitrailer registered in this state unless such policy provides coverage in amounts or limits prescribed for bodily injury or death for a liability policy under this chapter, under provisions approved by the insurance commissioner, for the protection of persons insured thereunder who are legally entitled to recover damages from owners or operators of uninsured motor vehicles, trailers or semitrailers and hit-and-run motor vehicles because of bodily injury, sickness or disease, including death resulting therefrom; and, subject to the terms and conditions of such coverage, such coverage shall include an insured motor vehicle where the liability insurer thereof is unable to make payment with respect to the legal liability of its insured within the limits specified therein because of insolvency.

(2) For the purpose of said coverage, if the policyholder or obligor elects to purchase the coverage described in this paragraph, the term ''uninsured motor vehicle'' shall also include protection of persons insured thereunder who are legally entitled to recover damages from owners or operators of insured motor vehicles, trailers or semitrailers, to which a bodily injury liability bond or policy applies at the time of the accident and its bodily injury liability bond amount or policy limit is less than the policy limit for uninsured motor vehicle coverage and is insufficient to satisfy the damages of persons insured thereunder and only to the extent that the uninsured motor vehicle coverage limits exceed said limits of bodily injury liability subject to the terms of the policy. The amounts recoverable hereunder shall not be affected by any statutory limits of liability applicable to the tortfeasor, including, but not limited to, amounts recoverable under section fifteen of chapter eighty-four, sections eighty-five G and eighty-five K of chapter two hundred and thirty-one, and section two of chapter two hundred and fifty-eight. The policyholder or obligor shall be notified that he may elect to purchase the said coverage, and such notification shall be at such times and in a manner prescribed by the commissioner of insurance.

(3) An insurer's extension of coverage as provided in paragraph (2) shall be applicable only to accidents occurring during a policy period in which its insured's uninsured motor vehicle coverage is in effect and where the liability insurer of the tort-feasor has been declared to be insolvent by a court of competent jurisdiction as of the accident date, or has been declared to be insolvent by a court of competent jurisdiction within one year after the accident date. Nothing herein contained shall be construed to prevent any insurer from extending coverage under the terms and conditions more favorable to its insured than is provided hereunder.

(4) In the event of payment to any person under the coverage provided by this section and subject to the terms and conditions of such coverage, the insurer making such payment shall, to the extent thereof, be entitled to the proceeds of any settlement or judgment resulting from the exercise of any rights of recovery of such person against any person or organization legally responsible for the bodily injury for which such payment is made, including the proceeds recoverable from the assets of the insolvent insurer; provided, however, that, subject to the definitions and limitations of uninsured motor vehicle coverage set forth in paragraphs (1) and (2), the insurer shall not be entitled to any such proceeds unless and until the person insured under the coverage required or elected to be purchased under this section has received full compensation for his injuries, including death resulting therefrom; and provided, further, that with respect to payments made by reason of the extension of coverage described in paragraphs (2) and (3), the insurer making such payment shall not be entitled to any right of recovery against such tort-feasor in excess of the proceeds recovered from such insolvent insurer of said tort-feasor.

(5) Uninsured motorists coverage shall provide that regardless of the number of vehicles involved, whether insured or not, persons covered, claims made, premiums paid or the number of premiums shown on the policy, in no event shall the limit of liability for two or more vehicles or two or more policies be added together combined or stacked to determine the limits of insurance coverage available to injured persons. An insured who is not a named insured on any policy providing uninsured motorist coverage may recover only from the policy of a resident relative providing the highest limits of such coverage whether or not such vehicle was involved in the accident; provided, however, if there are two or more such policies which provide such coverage at the same limits a pro rata contribution will be made. Any injured occupants who are not named insureds on a policy and who are not insured on a resident relative's policy may obtain uninsured motorist coverage from the named insured's policy covering the vehicle they occupy when injured. A person who is a named insured and who suffers bodily injury or death:

(a) while occupying a nonowned motor vehicle registered for highway use may recover only from the policy providing the highest limits of uninsured motorist coverage on which such person is the named insured, provided, however, if there are two or more such policies which provide such coverage at the same limits a pro rata contribution will be made;

(b) while occupying an owned motor vehicle registered for highway use and which had in effect the coverage required by this section shall recover uninsured motorist coverage only from the policy covering such occupied vehicle, provided, however, if there are two or more such policies, a pro rata contribution will be made. An insured who suffers bodily injury or death while occupying a motor vehicle owned by that insured which is registered for highway use and does not have in effect the coverage required by section thirty-four A of chapter ninety may not recover uninsured motorist coverage from any policy. No uninsured motorist coverage shall apply from any policy if a named insured suffers bodily injury or death while occupying an owned motor vehicle registered for highway use being used at the time as a public or livery conveyance and which is not insured for uninsured motorist coverage.