With the approval of the Department, the payment of any indebtedness hereafter incurred in the construction of any road or grade separation selected under the provisions of Section 6-701.1 as a road or grade separation to be constructed under Section 6-701.1 and the payment of engineering costs incurred in connection therewith; but if the road district desires to use motor fuel tax funds for this purpose it shall follow the same procedure in expending moneys secured in the creation of the indebtedness as if the construction was to be paid for directly with motor fuel tax funds under the provisions of Section 6-701.1.