N.J. Stat. Ann. § 54:8A-21

So much of the moneys as may be in the Transportation Fund at any time and as may be in excess of the amounts needed to meet anticipated uses thereof pursuant to this act during any fiscal year, shall be held and accumulated as an endowment fund, and may be invested and reinvested from time to time, in the same manner as any State funds may be invested, and the income thereof, as well as so much of the principal as may be necessary from time to time, shall be applied to the purposes authorized for the said Transportation Fund, within the limits of available appropriations.