When the commissioner has or shall have approved a contract made in accordance with section 27:9-1 of this title and the payments thereunder, he shall within six years after the date of such approval, if funds be on hand available for the purpose, take over the highway so constructed by a county in accordance with the terms of sections 27:9-1 to 27:9-5 of this title and pay to the county the actual cost of the construction thereof. The sum so paid, or such part thereof as may be necessary, shall be used for the purpose of retiring any bonds or other obligations issued for the purpose of raising funds for the construction of the road.

No road constructed by a county under said sections 27:9-1 to 27:9-5 shall be taken over and paid for by the commissioner unless the state highway engineer shall certify to the commissioner that the road has been constructed in all respects in accordance with the plans and specifications approved by the commissioner, but the commissioner may, if funds be available and have been set aside for the purpose of reimbursing a county for the construction and improvement of a highway made by a county under said sections, pay to the county the amount already expended if the state highway engineer shall certify to the commissioner that the work has been done in accordance with the plans and specifications approved by the commissioner to the value of the amount requested.