§ 21. This section and the preceding sections hereof, except section
eighteen, constitute an agreement between the states of New York and New
Jersey supplementary to the compact between the two states dated April
thirty, nineteen hundred twenty-one, and amendatory thereof, and shall
be liberally construed to effectuate the purposes of said compact and of
the comprehensive plan heretofore adopted by the two states, and any
powers granted to the port authority by this act shall be deemed to be
in aid of and supplementary to and in no case a limitation upon the
powers heretofore vested in the port authority by the two said states
and/or by congress, except as herein otherwise provided.

Any declarations contained in this act with respect to the
governmental nature of bridges and tunnels and to the exemption of
bridge and tunnel property from taxation and to the discretion of the
port authority with respect to bridge and tunnel operations shall not be
construed to imply that other port authority property and operations are
not of a governmental nature, or that they are subject to taxation, or
that the determinations of the port authority with respect thereto are
not conclusive.

The powers vested in the port authority herein (including but not
limited to the powers to acquire real property by condemnation and to
make or effectuate additions, improvements, approaches and connections)
shall be continuing powers and no exercise thereof shall be deemed to
exhaust them or any of them.