N.J. Stat. § 40:56-50
The governing body of any municipality in which said improvement is undertaken may, by and with the consent of the state highway commission, enter into a contract with the board of chosen freeholders of the county in which said municipality lies, or with the state highway commission, to pay the entire additional cost due to said increased width of improvement and paving, which contract shall fix and prescribe the time and manner of payment by said municipality of such added cost and expense; or the said municipality may make such improvement in the same manner as improvements are made therein, by its governing body, provided, the contract for such improvement shall be approved by the state highway commission.
The contract shall not be entered into unless and until the proceedings and acts for the undertaking of a local or general improvement have been taken and performed in the manner prescribed by this chapter.
N.J.S. § 40:56-50