If any county, civil subdivision or persons interested desire a road of a higher type, more expensive construction, or better in any way than the road proposed by the department, and shall secure to the state, in the manner and within the time prescribed by the commission, the additional cost of such road, then such road shall be constructed with the funds of the state and funds so secured; provided, however, that the road shall be constructed under the supervision and direction of the commission, as provided for in section 227.030, for the construction of roads at the sole cost of the state.