N.J. Stat. Ann. § 27:7-16

In lieu of making the improvement in the manner provided in section 27:7-15 of this title, the municipality, upon the approval of such proceedings by the commissioner may contract with the commissioner for the making of the improvement and the payment to the state of the cost thereof as fixed by the contract, or if the improvement of the state highway shall be undertaken by the county pursuant to sections 27:9-1 to 27:9-5 of this title, the municipality may contract with the county for the making of the improvement and the payment to the county of the cost thereof as fixed by the contract.