Section 11D. Upon acceptance of this section as hereinafter provided, the appropriate public authority of the governmental unit shall negotiate with insurance companies or savings banks and purchase on such terms as it deems to be in the best interest of the governmental unit and those persons employed as police officers and firefighters and defined as employees in section two a policy or policies of group accidental death insurance payable on behalf of a police officer or firefighter who dies as the natural and proximate result of a bodily injury accidentally sustained or a hazard undergone as a result of and while in the performance of his official duties as an employee of the governmental unit and not as an employee of a private organization, at some definite place and at some definite time on and after the date of his becoming insured hereunder, and without serious and wilful misconduct on his part.

The appropriate public authority shall incorporate this accidental death insurance as an integral part of the coverage provided under section eleven A, or, provide a policy of accidental death insurance for said employees with the claim experience and retention costs maintained unrelated to the claim experience and retention costs applicable to any policy or policies of group life and accidental death and dismemberment insurance in effect as provided under said section eleven A, but, in either event, the aforementioned employees shall be insured for group accidental death insurance authorized by this section for twice the maximum amount to which the policeman or fireman would be entitled if insured for the maximum amount of group accidental death and dismemberment insurance provided under section eleven A whether or not said employee is insured for such maximum amount under said section eleven A.

Such accidental death insurance shall be issued by the carrier or carriers as determined by the appropriate public authority for a period not exceeding five years, and such insurance shall be issued without regard to a minimum number of eligible policemen or firemen or to the provisions of chapter one hundred and seventy-five.

Each policeman and fireman entitled to be insured under this section shall file an application therefor with the treasurer of the governmental unit on an appropriate form prescribed by said treasurer, except that a policeman or fireman having such accidental death insurance who becomes entitled to further accidental death insurance hereunder by reason of an increase in annual salary shall automatically be insured for the amount of such further accidental death insurance to become effective on the first day of the second month following the month in which the increase was granted provided that such increase in salary has been authorized for a period of time in excess of one year. No reduction in the amount of accidental death insurance shall be required on account of a reduction in salary or compensation. For purposes of this accidental death insurance, yearly gross salary or compensation shall not include any overtime pay.

With respect to any accidental death insurance which is in effect for a policeman or fireman there shall be withheld from each payment of salary, wages or compensation fifty per cent of a premium the amount of which may be changed by the governmental unit from time to time as part of the total cost for such accidental death insurance. The governmental unit shall contribute the remaining fifty per cent of said premium together with payment in full of a subsidiary or additional rate which rate may be lower or higher than the governmental unit's share of the aforesaid premium. If a policeman or fireman is not entitled to receive salary, wages or other compensation for a calendar or premium month while in the status of leave of absence without pay, he shall make payment directly to the treasurer of the governmental unit and there shall be no contribution by the governmental unit for such payment.

A policeman or fireman insured under this section may by written notice on a form provided by the treasurer cancel such accidental death insurance and such insurance shall require no further premium payment the first day of the premium month following the expiration of fifteen days from the receipt of notice of cancellation. Accidental death insurance coverage will therefore terminate at the end of the month for which premium has been paid.

Upon retirement of a policeman or fireman eligible for pension allowances under any general or special law the accidental death insurance provided under this section shall terminate.

Any dividend or refund applicable to the accidental death insurance provided under this section shall be paid by the insurance carrier or carriers to the governmental unit and shall then be distributed in accordance with the provisions of section eight or eight A whichever may be applicable.

The appropriate public authorities of two or more governmental units, irrespective of the county, may join together in negotiating and purchasing one or more policies of accidental death insurance as prescribed in section twelve.

This section shall take effect in a county, except Worcester county, city, town or district upon its acceptance in the following manner:—In a county, except Worcester county by vote of the county commissioners; in a city having a Plan D or Plan E charter by a majority vote of its city council; in any other city by vote of its city council, approved by the mayor; in a district by vote of the governing board of the district; and in a town by submission for acceptance to the registered voters in the form of the following question which shall be printed upon the official ballot to be used at an election:—''Shall the town pay one half of a premium for group accidental death insurance for policemen and firemen who are killed or who die from accidental injuries received in the performance of their duties with such employee paying the remaining one half, and shall the town also pay a subsidiary or additional rate?''