Commissioners of any county, or the board of commissioners of any highway district, are empowered to cooperate with the state in the construction of highways or bridges, with aid from the United States or the state. The boards of commissioners are authorized to deposit with the treasurer of the state, to be placed in the state highway account, the amount of funds to be contributed by the county or highway district on any project for the improvement or construction of highways or bridges, which may be agreed upon in writing between the boards of commissioners and the board. The boards of commissioners are empowered to make deposits in advance of construction and at the time the agreement between the boards and the board is entered into. In the event the project for the improvement or construction of highways or bridges is not proceeded with, or in the event that all of the funds deposited by any board of commissioners for use on any project are not used in the completion of the project, the board shall repay any unused balances to the boards of commissioners having deposited these funds, and the state controller shall draw his warrant for the payment of those moneys out of the state highway account against claims duly approved by the board and the state board of examiners.