Ohio Rev. Code § 5540.18
A board of county commissioners may enter into an agreement with a contiguous transportation improvement district that the board of county commissioners did not create for the district to undertake a project that is located wholly or partially within that county provided that, the board of county commissioners of the county that created the transportation improvement district also must enter into the agreement.
No transportation improvement district shall undertake a project that is located wholly or partially within a county that did not create the transportation improvement district except pursuant to an agreement entered into in accordance with this section, a project being undertaken by two or more transportation improvement districts, or as otherwise provided by law.
R.C. § 5540.18