The executive director may carry on each motor vehicle of the department property damage insurance and uninsured and underinsured motorists coverage for any physical damage which is sustained by such motor vehicles while such motor vehicles are being operated by a duly authorized department employee in the performance of his official duties. The coverage authorized in this section shall be purchased in a policy or policies written by the agent or agents of an insurance company authorized to do, and doing business, in this state, and the amount of coverage purchased shall be determined by the executive director. Premiums on such policies shall be paid as are other expenses of the department.