Moneys appropriated to the department of transportation and derived from fees, excises, or license taxes relating to the registration, operation, or use of vehicles on public highways, or to fuels used for propelling such vehicle, shall not be expended for any purpose other than as provided in Section 5a of Article XII, Ohio Constitution, and such moneys may be expended only for expenses directly chargeable to the purposes set forth in such section. The director of transportation may make rules facilitating, to the extent practical under the circumstances, the use of public transportation systems and aviation systems by persons with disabilities.