Section 54-5-140 - Improvements by local governments - Approval - Maintenance(a) Cities, counties and metropolitan governments are authorized, within their respective jurisdictions, to make improvements to existing highways on the system of state highways, or to construct additions to the system, with the approval of the commissioner. The work may be accomplished by qualified persons provided by the city, county, or metropolitan government, or by contracts with qualified contractors.(b) When the work provided for in subsection (a) is undertaken, the commissioner shall have the authority to approve the plans and specifications for conformity to state standards. Following completion of the construction in conformity with the plans and specifications, the department shall assume responsibility for the maintenance of the highways.