Except for bonds issued under section 18c, bonds issued by a governmental unit under this act shall be serial bonds with periodic maturities, or term bonds, with mandatory redemption requirements, or both serial and term bonds, the aggregate of which shall not exceed 30 years, the first of which shall fall due not more than 5 years from the date of issuance. Maturities shall be as established by the resolution or ordinance authorizing the bonds or notes, without regard to the useful lives of the projects financed from the proceeds of the bonds or notes. The bonds shall bear interest, taking into account any discount or premium on the sale of the bonds, at a rate not exceeding the maximum rate permitted by the revised municipal finance act, 2001 PA 34, MCL 141.2101 to 141.2821, may be made redeemable before maturity on those terms and conditions, and with the premium as shall be provided by the proceedings authorizing their issuance. Outstanding and authorized bonds issued pursuant to this act may be treated as a single issue for the purpose of fixing maturities. If pursuant to 1952 PA 175, MCL 247.701 to 247.707, or in 1943 PA 143, MCL 141.251 to 141.254, the maximum annual principal and interest requirements on bonds issued by governmental units are required to be measured by reference to amounts received from the motor vehicle highway fund, the requirements shall be measured by the receipts from the motor vehicle highway fund, the Michigan transportation fund, or both funds, and if pursuant to this act the maximum annual principal and interest requirements on bonds or notes issued by governmental units are required to be measured by reference to amounts received from the Michigan transportation fund, the requirements shall be measured by the receipts from the motor vehicle highway fund, the Michigan transportation fund, or both funds. The state transportation commission shall certify, which certification shall, for purposes of the validity of bonds, notes, and other obligations, be conclusive as to the matters stated in the certification, to the state treasury on or before the issuance of any bonds, notes, or other obligations payable from and secured by a lien on the state trunk line fund, issued after July 1, 1983, pursuant to section 18b or 18d for purposes other than the preservation of highways, roads, streets, and bridges and for purposes other than the purposes specified in section 11(2)(b), (c), (d), (g), (h), and (i) that its average annual debt service requirements payable from and secured by a lien on the state trunk line fund for all bonds, notes, and other obligations, or portions of bonds, notes, and other obligations issued after July 1, 1983, for purposes other than the preservation of highways, roads, streets, and bridges and other than for the purposes specified in section 11(2)(b), (c), (d), (g), (h), and (i), including the bonds, notes, or other obligations to be issued does not exceed 10% of the state revenue appropriated to the state trunk line fund, less the amounts described in section 11(2)(a) to (i) during the last completed state fiscal year. The state transportation commission shall certify, which certification shall, for purposes of the validity of bonds, notes, or other certification, to the state treasury on or before the issuance of any bonds, notes, or other obligations issued after December 31, 2001, pursuant to section 18b(9) in anticipation of the receipt of grants from the United States or any agency or instrumentality of the United States for distributions to the credit of the state trunk line fund, and not payable from taxes deposited in the state trunk line fund, for purposes other than the preservation of highways, roads, streets, and bridges and for purposes other than the purposes specified in section 11(2)(b), (c), (f), and (i), that its average annual debt service requirements for all bonds, notes, and other obligations, or portions of bonds, notes, or other obligations issued after December 31, 2001, pursuant to section 18b(9) and not payable from taxes deposited in the state trunk line fund, for purposes other than the preservation of highways, roads, streets, and bridges and other than the purposes specified in section 11(2)(b), (c), (f), and (i), including the bonds, notes, or other obligations to be issued, do not exceed 10% of the federal revenue distributed to the credit of the state trunk line fund during the last completed state fiscal year. If the purpose for which the bonds, notes, or other obligations is issued is changed after the issuance of the bonds, notes, or other obligations, the change shall be made in a manner to maintain compliance with the certification required by the preceding sentence, as of the date the certificate was originally issued, but no change shall invalidate or otherwise affect the bonds, notes, or other obligations with respect to which the certificate was issued, or the obligation to pay debt service on the bonds, notes, or other obligations. As used in this section, "preservation" means preservation as defined in section 10c.