N.J. Stat. Ann. § 27:1C-12

The governing bodies of two or more counties which have established, or propose to establish, adjoining transportation development districts, and which have determined that joint or coordinated planning or implementation of transportation projects would be beneficial, may enter into joint arrangements under this act, including: (1) filing joint applications under section 4 of this act, (2) initiating a coordinated joint planning process under section 5 of this act, (3) adopting coordinated district transportation improvement plans under section 6 of this act and (4) entering into joint project agreements under section 9 of this act.