Ohio Rev. Code § 5525.11
The director of transportation may enter into any contract authorized by law upon a unit price basis. Where a contract is entered into upon a unit price basis, the contractor shall state in his bid the sum for which he offers to perform each unit of each different kind or class of work, and upon completion the quantities of each kind of work shall be measured and the contractor paid only for the quantities of work actually performed by him. Where the director elects to enter into a contract upon a unit price basis he may include in the estimate such reasonable sums as he deems necessary to cover variations in the actual quantities of work as compared with the estimated quantities. In the event the actual compensation earned by the contractor exceeds the estimate, any such excess shall be paid from any funds of the department of transportation which may be expended upon the improvement in question. In the event the actual compensation earned by the contractor is less than the estimate, the saving shall inure to the benefit of the state.
R.C. §5525.11