Laws enacted by the fifth legislature authorizing the issue and sale of state highway bonds for the purpose of providing funds for the construction and improvement of state highways and to enable the state to meet and secure allotments of federal funds to aid in construction and improvement of roads, and laws so enacted authorizing the issue and sale of state highway debentures to anticipate the collection of revenues from motor vehicle licenses and other revenues provided by law for the state road fund, shall take effect without submitting them to the electors of the state, and notwithstanding that the total indebtedness of the state may thereby temporarily exceed one per centum of the assessed valuation of all the property subject to taxation in the state. Provided, that the total amount of such state highway bonds payable from proceeds of taxes levied on property outstanding at any one time shall not exceed two million dollars [($2,000,000)]. The legislature shall not enact any law which will decrease the amount of the annual revenues pledged for the payment of state highway debentures or which will divert any of such revenues to any other purpose so long as any of the said debentures issued to anticipate the collection thereof remain unpaid.