(1) Upon completion of a preliminary proposal, the county submitting the proposal shall submit to the board its voucher for payment of the trust account share of the cost. Upon the completion of an approved rural arterial construction project, the county constructing the project shall submit to the board its voucher for the payment of the trust account share of the cost. The chair of the board or his or her designated agent shall approve such voucher when proper to do so, for payment from the rural arterial trust account to the county submitting the voucher.

(2) The board may adopt rules providing for the approval of payments of funds in the rural arterial trust account to a county for costs of preliminary proposal, and costs of construction of an approved project from time to time as work progresses. These payments shall at no time exceed the rural arterial trust account share of the costs of construction incurred to the date of the voucher covering the payment.