Bonds may be issued under the Nebraska Highway Bond Act only to the extent that the annual aggregate principal and interest requirements, in the calendar year in which such bonds are issued and in each calendar year thereafter until the scheduled maturity of such bonds, on such bonds and on all other bonds theretofore issued and to be outstanding and unpaid upon the issuance of such bonds shall not exceed the amount which is equal to fifty percent of the money deposited in the fund, the State Highway Capital Improvement Fund, or the bond fund, as the case may be, from which such bonds shall be paid during the calendar year preceding the issuance of the bonds proposed to be issued. This section shall not apply to the first issuance of each series of bonds authorized by the Legislature.

If short-term bonds are issued in anticipation of the issuance of long-term refunding bonds and such short-term bonds are secured by insurance or a letter of credit or similar guarantee issued by a financial institution rated by a national rating agency in one of the two highest categories of bond ratings, then, for the purposes of the Nebraska Highway Bond Act, when determining the amount of short-term bonds that may be issued and the amount of taxes, fees, or other money to be deposited in any fund for the payment of bonds issued under the act, the annual aggregate principal and interest payments on the short-term bonds shall be deemed to be such payments thereon, except that the final principal payment shall not be that specified in the short-term bonds but shall be the principal and all interest payments required to reimburse the issuer of the insurance policy or letter of credit or similar guarantee pursuant to the reimbursement agreement between the commission and such issuer.