Ind. Code § 8-17-1-1
A county executive may construct, reconstruct, improve, and maintain all public highways, bridges, and culverts in the county, including highways, bridges, and culverts under the supervision of the department, if approved by the department, or located in municipalities, as provided in this chapter. In addition, the department may, after petitioning the affected county executive or municipal legislative body and obtaining approval, construct, reconstruct, improve, and maintain county or municipal highways. The department and a county or a municipality in the county through which a toll road project under IC 8-15-2 passes may jointly undertake transportation projects (as defined in IC 36-1-10-2). The duties and responsibilities of a joint undertaking shall be assigned to the department, the county, or the municipality in the county as the parties may agree.
IC 8-17-1-1