The commissioners provided for in section 40:37-19 of this title may employ such assistants as they may deem necessary and may expend such sums therefor and in the discharge of their duties, including the actual traveling expenses of the members, as they may deem expedient, not exceeding the sum of ten thousand dollars.
All expenditures shall, from time to time, be certified by them to the board of chosen freeholders who, if satisfied of the correctness thereof, shall order the county treasurer to pay the same out of the funds appropriated or to be appropriated for the maintenance of highways and bridges in the county or out of any unexpended balance.
N.J.S. § 40:37-20