Ind. Code § 8-23-9-3

Sec. 3. Except as provided in sections 4 and 4.5 of this chapter, the commissioner shall let the contract for the construction, improvement, or maintenance of the road to the lowest and best bidder. The determination of the lowest and best bidder must include any requirement imposed under section 13 of this chapter. The lowest and best bid may not be for a greater sum than the estimated cost of the project.