If the public body referred to in section 27:14-47 of this title shall not have sufficient funds with which to pay its share of the cost of such repairs, it may issue bonds in a sum not exceeding the sum to be advanced by the commissioner for and towards such repairs as stated in its certificate, to defray and pay its share of the costs.

The commissioner may, in his discretion, approve and permit the use of not more than fifty per cent of the motor vehicle fund allotment made by the state to the counties each year to be used toward the payment of interest on such bonds, and for the retirement of such bonds, except that he shall not permit the use of the state motor vehicle funds for such purposes in an amount which, if subtracted from the total allotment by the state to the county would, in the opinion of the commissioner, leave an amount insufficient for the proper repair and maintenance of the other existing county roads.

No motor vehicle funds shall be used for any work or contract performed or entered into by a county prior to March twenty-sixth, one thousand nine hundred and nineteen.