N.J. Stat. Ann. § 27:3-1

When a road is being constructed, reconstructed or undergoing extraordinary repairs under the authority and direction of the board of chosen freeholders of a county, or the state highway commissioner, or by them jointly, and by reason thereof the road is closed to or rendered unfit for public travel, the body under whose authority and supervision the work is being done may provide a detour or detours over any other roads in the county, when the work is being done by the board of chosen freeholders, and over any other roads in the state when the work is being done by the state highway commissioner.