Ohio Rev. Code § 5528.37
The general assembly may from time to time repeal or reduce any fee, excise, or tax pledged pursuant to section 2i of Article VIII, Ohio Constitution, to the payment of the interest on or principal of the obligations issued pursuant to said section 2i and sections 5528.30 and 5528.31 of the Revised Code, and may levy any new or increased fee, excise, or tax relating to the registration, operation, or use of vehicles on the public highways, or to fuels used for propelling such vehicles, or any other excises and taxes of the state, to be available to meet the pledge of the state to the highway obligations, except ad valorem taxes on real or personal property and income taxes, provided that nothing in this section authorizes any impairment of the obligation of this state to levy and collect sufficient excises and taxes to pay highway obligations issued pursuant to section 2i of Article VIII, Ohio Constitution, and sections 5528.30 and 5528.31 of the Revised Code for which other provision is not made.
R.C. § 5528.37