When a county board employs a person and places in his or her charge and under his or her supervision trucks, automobiles, snowplows, road graders, or other vehicles and authorizes such employee to use them upon a public road, the county board shall purchase liability insurance to protect any such employee against loss occasioned by any acts of negligence resulting from the use of such vehicles or equipment. The insurance shall be purchased by public bidding at least once every three years in a limit of not less than one hundred thousand dollars to cover the bodily injury or injuries of one person and, subject to the limitation to one person, one million dollars to cover bodily injury or injuries to more than one person in the same accident and one hundred thousand dollars to cover property damage. The insurance policy may, in the discretion of the county board, contain a deductible provision for up to one thousand dollars of any claim in which event the county shall be considered a self-insurer for that amount. The insurance and bidding requirements of this section shall not apply to a county which is a member of a risk management pool formed pursuant to the Intergovernmental Risk Management Act. Any judgment against any employee shall not be collectible in whole or in part from any member of the county board.