NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
being done in connection with this case, at the time the opinion is issued.
The syllabus constitutes no part of the opinion of the Court but has been
prepared by the Reporter of Decisions for the convenience of the reader.
See United States v. Detroit Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

NATIONAL RAILROAD PASSENGER CORPORATION
et al. v. BOSTON & MAINE CORP. et al.
certiorari to the united states court of appeals for
the district of columbia circuit
No. 90-1419.   Argued January 13, 1992-Decided March 25, 1992

The Rail Passenger Service Act of 1970 (RPSA) created petitioner
 National Railroad Passenger Corporation (Amtrak), a private corpora-
 tion, to provide intercity and commuter rail passenger service.  The
 Act permits Amtrak to enter into ``trackage rights'' agreements to use
 tracks owned and used by freight railroads, 45 U.S.C. 562(a); and
 allows Amtrak to ask petitioner Interstate Commerce Commission
 (ICC) to condemn railroad property ``required for intercity rail
 passenger service'' if Amtrak and the railroad cannot agree upon sale
 terms, 562(d).  For purposes of the ICC's condemnation order,
 Amtrak's ``need for the property'' ``shall be deemed to be established''
 unless the conveyance will significantly impair the railroad's ability
 to carry out its obligations as a common carrier and unless Amtrak's
 obligations can adequately be met by the acquisition of alternative
 property.  Ibid.  Amtrak had a trackage rights agreement with
 respondent Boston and Maine Corporation (B&M) to operate its
 ``Montrealer'' train between Washington, D. C., and Montreal.
 Amtrak claims it was forced to discontinue this service because of
 B&M's poor maintenance of its track segment.  Subsequently, Amtrak
 entered into an agreement with petitioner Central Vermont Railroad
 (CV) which provided that, among other things, Amtrak would acquire
 the B&M track and reconvey it to CV, and CV would grant trackage
 rights to Amtrak and usage rights to B&M.  When B&M did not
 accept Amtrak's purchase offer for the track, Amtrak sought and
 received an ICC order compelling conveyance for just compensation.
 The ICC found, among other things, that 562(d) created a statutory
 presumption of Amtrak's need for the track, which B&M failed to
 rebut.  The Court of Appeals remanded the case for further proceed-
 ings, concluding that, because Amtrak did not intend to retain the
 track, it needed only its use, not its ownership.  While petitions for
 rehearing were pending, 562(d) was amended to allow Amtrak to
 subsequently convey title to acquired property to a third party if the
 ICC finds the reconveyance furthers the RPSA's purposes.  Nonethe-
 less, the court denied rehearing, holding that the condemnation was
 not valid because the property was not ``required for intercity rail
 passenger service.''
Held:
   1.The ICC's decision was based on a reasonable interpretation and
 application of 562(d).  Pp.8-15.
    (a)The ICC's interpretation of the word ``required'' is due
 deference as a reasonable interpretation of an ambiguous term in a
 statute that the ICC administers.  See, e. g., Chevron U. S. A. Inc.
 v. Natural Resources Defense Council, Inc., 467 U.S. 837.  The
 existence of alternative dictionary definitions for ``required'' indicates
 that the statute is open to interpretation.  The ICC's interpretation
 gives effect to 562(d)'s presumption of need.  In contrast, the Court
 of Appeals' view-that ``required'' establishes a separate condition
 that Amtrak's condemnation authority is limited to property that is
 indispensable to its operations-is in clear tension with the pre-
 sumption.  In addition, 562(d)'s amendment confirms the ICC's
 definition, while the Court of Appeals' strict rule would make the
 amendment superfluous by barring condemnation whenever Amtrak's
 purpose is to reconvey property.  Pp.8-12.
    (b)The ICC was not required to make specific findings regarding
 Amtrak's actual need for the condemnation because its oversight
 responsibility is limited to ensuring that condemned property will be
 used in Amtrak's rail operations.  The statute's structure and its
 presumption of need create a strong inference that it authorizes
 Amtrak to make a reasonable business judgment that condemnation
 is advisable, unless the statutory presumption is rebutted.  P.12.
    (c)B&M's several arguments against the ICC's interpretation are
 rejected.  The eminent domain power has been given to the ICC, not
 a private entitythus is not limited as suggested by cases such
 as United States v. Carmack, 329 U.S. 230, 243, n.13.  Further-
 more, this case turns on the need for deference to the agency, not to
 Amtrak.  The ICC's interpretation of 562(d) also did not violate the
 ``public use'' requirement of the Fifth Amendment's Takings Clause,
 since the agency's determination that the condemnation will serve a
 public purpose by facilitating Amtrak's rail service was not irrational.
 See, e. g., Hawaii Housing Authority v. Midkiff, 467 U.S. 229,
 240-241.  Moreover, the agency did not err in concluding that the
 statutory prerequisite that the parties were ``unable to agree upon
 terms for the sale'' mandated nothing more than a factual determina-
 tion that they would be unable to reach agreement through further
 negotiations.  Nor did it make inadequate factual findings in conclud-
 ing that B&M had not rebutted the presumption of need.  The ICC
 was not unreasonable in considering the effect of trackage rights and
 the just compensation award in assessing whether the conveyance
 would significantly impair B&M's ability to carry out its obligations,
 or in interpreting the availability-of-alternative-property provision as
 referring only to whether Amtrak could provide service using an
 alternative route, not whether a lesser interest in property would
 suffice to meet Amtrak's needs.  Pp.13-15.
   2.The parties' challenges to the ICC's just compensation finding
 as well as certain other issues should be resolved on remand.
 Pp.15-16.
286 U.S. App. D.C. 1, 911 F.2d 743, reversed and remanded.

 Kennedy, J., delivered the opinion of the Court, in which Rehnquist,
C. J., and Stevens, O'Connor, Scalia, and Souter, JJ., joined.
White, J., filed a dissenting opinion, in which Blackmun and Thomas,
JJ., joined.
-------------------------------



Notice: This opinion is subject to formal revision before publication in the
preliminary print of the United States Reports.  Readers are requested to
notify the Reporter of Decisions, Supreme Court of the United States, Wash-
ington, D.C. 20543, of any typographical or other formal errors, in order that
corrections may be made before the preliminary print goes to press.
SUPREME COURT OF THE UNITED STATES
                        --------
                Nos. 90-1419 and 90-1769
                        --------
        NATIONAL RAILROAD PASSENGER CORPORATION,
                   et al., PETITIONERS
90-1419                     v.
           BOSTON AND MAINE CORPORATION et al.

           INTERSTATE COMMERCE SION AND
               UNITED STATES, PETITIONERS
90-1769                     v.
           BOSTON AND MAINE CORPORATION et al.
  on writs of certiorari to the united states court of
      appeals for the district of columbia circuit
                    [March 25, 1992]

  Justice Kennedy delivered the opinion of the Court.
  The Interstate Commerce Commission (ICC) issued an
order, upon the request of petitioner National Railroad
Passenger Corporation, requiring conveyance of 48.8 miles
of railroad track from respondent Boston and Maine
Corporation (B&M) to the Corporation.  In these consolidat-
ed cases we must decide whether the ICC's decision was
based on a reasonable interpretation and application of
402(d) of the Rail Passenger Service Act, 45 U. S. C.
562(d), the statute the Corporation invoked in the proceed-
ing.  We hold the ICC's decision is authorized by the
statute, and so reverse the judgment of the Court of
Appeals for the District of Columbia Circuit, which set
aside the agency's action.
                            I
  The National Railroad Passenger Corporation, or Amtrak,
is a private, for-profit corporation created by Congress in
the Rail Passenger Service Act of 1970 (RPSA), Pub. L.
91-518, 84 Stat. 1328, 45 U. S. C. 501 et seq.  The purpose
of Amtrak is to provide modern and efficient intercity and
commuter rail passenger service.  501, 541.  Amtrak is
not an agency or instrumentality of the United States
Government, 541, but it has been supported over the years
by congressional appropriations.  Most of Amtrak's passen-
ger trains run over existing track systems owned and used
by freight railroads.  In the RPSA Congress authorized
Amtrak to enter into ``trackage rights'' agreements which
would allow Amtrak to use those tracks.  When Amtrak and
a freight railroad are unable to agree on the terms of such
an agreement, Amtrak may request the ICC to order the
track to be provided on reasonable terms.  562(a).
  In 1973 Congress amended the RPSA to add subsection
(d) of 402, 45 U. S. C. 562(d).  Section 562(d) provides in
pertinent part:
    ``(1) If the Corporation [Amtrak] and a railroad are
    unable to agree upon terms for the sale to the Corpora-
    tion of property (including interests in property) owned
    by the railroad and required for intercity rail passenger
    service, the Corporation may apply to the Commission
    [ICC] for an order establishing the need of the Corpora-
    tion for the property at issue and requiring the convey-
    ance thereof from the railroad to the Corporation on
    reasonable terms and conditions, including just com-
    pensation.  Unless the Commission finds that-
    ``(A) conveyance of the property to the Corporation
    would significantly impair the ability of the railroad to
    carry out its obligations as a common carrier; and
    ``(B) the obligations of the Corporation to provide
    modern, efficient, and economical rail passenger service
    can adequately be met by the acquisition of alternative
    property (including interests in property) which is
    available for sale on reasonable terms to the Corpora-
    tion, or available to the Corporation by the exercise of
    its authority under section 545(d) of this title,

    ``the need of the Corporation for the property shall be
    deemed to be established and the Commission shall
    order the conveyance of the property to the Corporation
    on such reasonable terms and conditions as it may
    prescribe, including just compensation.''
Amtrak may condemn nonrail property under a somewhat
similar provision, 545(d), a statute not at issue here.
  The Amtrak train the ``Montrealer'' began offering
passenger service between Washington, D.C. and Montreal
in 1972.  In parts of Massachusetts, Vermont, and New
Hampshire the train used the tracks of the Connecticut
River Line (Conn River Line), portions of which are owned
by B&M and other portions by the Central Vermont
Railroad (CV).  B&M and CV have operated freight trains
on the Conn River Line under reciprocal trackage rights
agreements dating back to 1930.
  In 1977 Amtrak entered into a trackage rights agreement
with B&M under which B&M agreed to maintain its
portions of the Conn River Line.  Those portions include a
48.8 mile segment of track on the Conn River Line between
Brattleboro and Windsor, Vermont.  This is the segment of
track at issue here.  At first the arrangement to maintain
the track proceeded well, but in the early 1980's problems
developed.  Guilford Transportation Industries, Inc., pur-
chased B&M out of bankruptcy, and purchased also a
railroad operating a parallel line.  Amtrak's claim is that
neglect of track maintenance resulting from this purchase
caused delays in Montrealer service.  Maintenance of the
Brattleboro-Windsor track was so poor that at points the
train was slowed to five miles an hour.  Negotiations for
better maintenance were unsuccessful.  In April 1987
Amtrak was forced to discontinue its Montrealer service.

  Congress responded to these events in July of 1987 by
appropriating $5 million to upgrade the Montrealer route.
Act of July 11, 1987, Pub. L. 100-71, 101 Stat. 447-448.
Amtrak decided not to spend the money to upgrade the
Conn River Line while B&M continued to own it, because
in Amtrak's view B&M could not be relied upon to maintain
the track once restored.  Amtrak began negotiations with
CV, and in early 1988 reached a preliminary agreement.
Amtrak promised to use its statutory condemnation power
to acquire the 48.8 miles of track in question, to at once
reconvey the track to CV, and to provide up to $3.1 million
to upgrade and rehabilitate the segment.  In return, CV
promised to provide the balance of the funds necessary to
upgrade the track, to maintain the track for 20 years in a
condition meeting Amtrak's standards, to grant Amtrak
trackage rights for 20 years, and to grant B&M trackage
rights to serve its existing customers.  As a prerequisite
to invoking 562(d), Amtrak made an offer to B&M to
purchase the segment for $1 million, on a take-it-or-leave-it
basis.  B&M offered to negotiate the terms under which it
would be willing to upgrade the segment, and stated, ``it
appears clear that there is no need to pursue the very
complex `offer to purchase' set forth in your letter.''  App.
60.  B&M's refusal to accept the offer seems to have been
anticipated by Amtrak and CV, as indicated by an internal
CV Memorandum written in January, 1988.  App. 94.
  Interpreting the B&M communication as a rejection of its
offer, Amtrak instituted this proceeding before the ICC to
compel conveyance of the track.  CV filed a simultaneous
request for an exemption from ICC regulation for its
acquisition of the segment upon reconveyance from Amtrak.
  B&M assessed the transaction as a significant shift in its
long competition with CV for freight traffic.  CV already
owned large parts of the Conn River Line and after the
proposed transaction it would own most of it.  Though
B&M would have trackage rights, CV would gain not only
ownership of the segment, but also the right to obtain
new customers on its route.  B&M alleged this gave a
new advantage to CV's corporate parent, the Canadian
National Railway Company, for each railroad links up with
competing companies in Canada.  CV's lines link to Canadi-
an National, while B&M's lines link to the Canadian
Pacific, Ltd., Canadian National's competitor.  B&M
challenged the transaction as simply a device to shift
ownership among railroads, not to give ownership to
Amtrak which, B&M argued, was the sole purpose of the
condemnation provision.
  B&M filed initial objections to the 562(d) proceeding on
two grounds:  that Amtrak had not shown that the parties
were unable to agree on reasonable terms of sale, and that
562(d) did not authorize condemnation of railroad lines.
The ICC rejected B&M's arguments and in a condemnation
proceeding held that Amtrak had shown the inability of the
parties to agree to terms.  It ruled that 562(d) covers
railroad tracks because tracks are ``rail property `required
for intercity rail passenger service.'''  App. to Pet. for Cert.
in No. 90-1419, pp. 130a-133a.  B&M next sought to
convert the proceeding into a trackage rights proceeding
under 562(a), but the ICC again rejected B&M's position,
holding that Amtrak had an ``election of remedies'' under
562 and so had no obligation to seek trackage rights under
subsection (a) before invoking subsection (d).  Id., at
115a-116a.  Meanwhile, CV and the States of Vermont and
Massachusetts, as well as numerous other parties, inter-
vened in the ICC proceeding.  (CV appears as a petitioner
before this Court, and Vermont and Massachusetts support
petitioners.)
  This was the first decided case involving Amtrak's
condemnation powers under 562(d).  Id., at 39a.  The ICC
issued its final decision in 1988 and ordered conveyance of
the segment with just compensation of $2,373,286.  It
reaffirmed earlier rulings and found that Amtrak ``ha[d]
met the statutory criteria for the institution of a proceed-
ing'' under 562(d).  Id., at 40a-42a, 81a.
  The ICC concluded that the presumption of Amtrak's
need for the track contained in 562(d)(1) was applicable.
In its view both statutory criteria must be met to rebut the
presumption, and B&M had established neither.  As to
alternative property (subsection (B)), the ICC found that no
reasonable alternative route existed for the Montrealer
service.  And as to significant impairment of B&M's ability
to carry out its common carrier obligations (subsection (A)),
the ICC found that because B&M had been awarded just
compensation and could continue to serve its customers
under the trackage rights agreement which was part of the
transaction, its ability had not been impaired.  Id., at
45a-46a.  The bulk of the ICC's final decision deals with
the question of just compensation, which is not before this
Court.  See infra.
  On petition for review, a divided panel of the Court of
Appeals for the District of Columbia Circuit granted the
petition and remanded the matter to the ICC for further
proceedings.  286 U. S. App. D.C. 1, 911 F.2d 743 (1990).
The majority held that 562(d) does not permit Amtrak to
condemn railroad property which it intends to reconvey to
another railroad.  It acknowledged that the ICC had
interpreted 562 in a different way, and that in the usual
course judicial deference would be given to its interpreta-
tion under the principles enunciated in Chevron U.S.A. Inc.
v. Natural Resources Defense Council, Inc., 467 U. S. 837
(1984); but the court concluded 562(d) is unambiguous in
light of its language and history, and so no deference was
due.  The panel majority reasoned that because Amtrak did
not intend to retain the track to be condemned, it needed
only its use, not its ownership.  As Amtrak could obtain use
of the property by obtaining either a trackage rights agree-
ment under 562(a), or by condemning an easement under
562(d), the entire fee interest was not ```required for
intercity rail passenger service.'''  286 U. S. App. D.C., at 8,
911 F.2d, at 750.  The majority stated that its holding was
confirmed by other considerations, including:  (1) the
potential constitutional problems, under the Takings
Clause, raised by the ICC's interpretation of 562(d); (2)
the structure of 562, which indicated an intent on the part
of Congress to relegate Amtrak to trackage rights under
562(a) when seeking only the use of track; and (3) Con-
gress' policy against cross-subsidization between sectors of
the railroad industry, which the majority concluded would
have been violated by this transaction.  Judge Ruth B.
Ginsburg concurred separately, rejecting the majority's
interpretation of the statute, but concluding that a remand
to the ICC was necessary because the ICC had not made
adequate findings to determine whether Amtrak in fact
needed to shift ownership of the segment from B&M to CV
to protect its interests.  Id., at 11-13, 911 F.2d, at 753-755.
This factual question, whether Amtrak's portrayal of a
recalcitrant B&M is accurate, remains in dispute.  Under
our resolution of the case, however, the issue need not be
reached.
  Amtrak and the ICC filed petitions for rehearing, and
while the petitions were pending Congress amended
562(d).  The amendment, adopted in specific response to
the Court of Appeals' decision in this case, added the
following sentence to 562(d)(1):  ``The Corporation may
subsequently convey title or other interest in such property
to a third party, if such reconveyance is found by the
Commission to further the purposes of this Act.''  Indepen-
dent Safety Board Act Amendments of 1990 9(a), Pub. L.
101-641, 104 Stat. 4658.  The amendment was made
applicable to all pending cases, 9(b), and B&M does not
dispute that it applied in this case even while it was before
the Court of Appeals on rehearing.  Brief for Respondent
B&M 33-35.  The Court of Appeals considered the 1990
amendment, but denied rehearing nonetheless.  288 U. S.
App. D.C. 196, 925 F.2d 427 (1991).  The panel majority
held that while 9 made it clear Amtrak was authorized to
reconvey condemned property ``subsequent to a condemna-
tion that is otherwise valid under [562(d)],'' it did not
change the statutory limitation that the property be
```required for intercity rail passenger service''' in the first
place.  Id., at 197, 925 F. 2d, at 428 (emphasis in original).
The majority reasoned that since its original decision was
based on Amtrak's failure to satisfy that requirement, the
amendment did not affect its holding.  The majority also
distinguished a case from the Second Circuit, National R.R.
Passenger Corp. v. Two Parcels of Land, 822 F.2d 1261
(1987), cert. denied 484 U. S. 954, which had interpreted
545(d)(1) (the provision authorizing Amtrak to condemn
nonrail property) to permit reconveyance following condem-
nation.  288 U. S. App. D.C., at 196-197, 425 F. 2d, at
427-428.  In a separate opinion, Judge Ginsburg wrote that
the amendment confirmed her view that the ICC had not
misinterpreted the statute, but that a remand remained
necessary for furtheual determinations.
  Amtrak and CV, in No. 90-1419, and the ICC, in No.
90-1769, filed separate petitions seeking review of the
Court of Appeals' decision.  We granted certiorari and
consolidated the cases.  502 U. S. --- (1991).  We now
reverse.
                           II
  The primary question raised by the case is a straightfor-
ward matter of statutory interpretation:  whether 562(d),
as amended, authorizes the condemnation and transaction
approved by the ICC but set aside by the Court of Appeals.
The Court of Appeals disallowed the transaction based on
its own interpretation of the language ``required for inter-
city rail passenger service'' in 562(d)(1).  In so holding it
limited Amtrak's condemnation authority to property which
was necessary, in the sense of indispensable, to Amtrak's
operations.  The ICC interpreted the relevant statutory
language to give Amtrak more latitude, and it is our task
to determine whether the agency had authority for its
statutory interpretation.
  Judicial deference to reasonable interpretations by an
agency of a statute that it administers is a dominant, well
settled principle of federal law.  We relied upon it in
Chevron U.S.A., supra, and have reaffirmed it often.  See,
e.g., K Mart Corp. v. Cartier, Inc., 486 U. S. 281, 292-293
(1988); Pauley v. Bethenergy Mines, Inc., 501 U. S. ---, ---
(1991).  These decisions mandate that when a court is
reviewing an agency decision based on a statutory interpre-
tation, ``if the statute is silent or ambiguous with respect to
the specific issue, the question for the court is whether the
agency's answer is based on a permissible construction of
the statute.''  Chevron U.S.A., 467 U. S., at 843.  If the
agency interpretation is not in conflict with the plain
language of the statute, deference is due.  K Mart Corp.,
486 U. S., at 292.  In ascertaining whether the agency's
interpretation is a permissible construction of the language,
a court must look to the structure and language of the
statute as a whole.  Id., at 291; Sullivan v. Everhart, 494
U. S. 83, --- (1990).  If the text is ambiguous and so open
to interpretation in some respects, a degree of deference is
granted to the agency, though a reviewing court need not
accept an interpretation which is unreasonable.
  Under these principles the ICC's interpretation of 562(d)
was permissible, and the Court of Appeals' decision was in
error to disregard it.  While the ICC's opinion is not explicit
in all of its details, the agency's decision is based on a
reading of the statute quite different from the Court of
Appeals'.  The ICC agreed that property Amtrak seeks to
condemn under 562(d) must be ``required for intercity rail
passenger service.''  It determined however that the word
``required'' need not mean, as the Court of Appeals' opinion
suggests, indispensable or necessary.  Instead, the ICC gave
effect to the statutory presumption of Amtrak's need for the
track, and in so doing implemented and interpreted the
statute in a manner that comports with its words and
structure.  The analysis of the Court of Appeals is inconsis-
tent with the agency's interpretation of the statutory
presumption of need.  The ICC's position before the Court
is that ``required'' can also mean ``useful or appropriate,''
Brief for Petitioners in No. 90-1769, p. 17, and that the
order under review adopted that meaning.  We agree that
the manner in which the ICC's applied the statute in this
case has that interpretation as its basic premise.  App. to
Pet. for Cert. in No. 90-1419, pp. 42a-46a.
  In its brief the ICC cites a dictionary definition in support
of its view.  Brief for Petitioners in No. 90-1769, p. 17,
citing Webster's Third New International Dictionary 1929
(1986).  The existence of alternative dictionary definitions
of the word ``required,'' each making some sense under the
statute, itself indicates that the statute is open to interpre-
tation.  See Sullivan v. Everhart, supra.  Few phrases in a
complex scheme of regulation are so clear as to be beyond
the need for interpretation when applied in a real context.
Further, the structure of the provision reinforces our
conclusion that statutory interpretation is appropriate and
that the Court of Appeals' interpretation is itself open to
serious question.  The court defined the word ``required,'' to
establish a separate condition that the property sought to
be condemned be necessary (indispensable) for Amtrak's
operations, a view which is not without support.  See e.g.,
American Heritage Dictionary of the English Language
1105 (1981).  This interpretation, though, leaves little
substance to the statutory presumption in favor of Amtrak's
need, and so is in clear tension with that part of the
statute.
  We decide that 562(d) is ambiguous in some respects
and conclude that the ICC's interpretation of the word
``required'' is a reasonable one.  We defer to its interpreta-
tion.  This is not to say that the issue is beyond dispute, but
these alternative interpretations are as old as the jurispru-
dence of this Court.  In McCulloch v. Maryland, 4 Wheat.
316, 413 (1819), Chief Justice Marshall, in a choice of
interpretations with some parallels to this one, read the
word ``necessary''  to mean ``convenient, or useful,'' rejecting
a stricter reading of the term which would have limited
congressional power under the Constitution to the ``most
direct and simple'' means available.  We think that as a
matter of definition and interpretation in the context of this
statute it is plausible, if not preferable, to say that Amtrak
can find that an acquisition is required when it is a useful
and appropriate way to accomplish its goals.
  The agency's interpretation is consistent also with the
1990 statutory addition enacted by the Congress.  While
the amendment does not modify the specific language of
562(d) at issue here, it confirms the ICC's view.  The
interpretation given to 562(d) by the Court of Appeals and
B&M, on the other hand, would make the amendment
superfluous, because if the word ``required'' has the strict
meaning they seek to attribute to it, condemnations by
Amtrak would seem to be barred whenever Amtrak's
purpose is to reconvey the property.
  Contrary to the position of the dissent, we are not
``deferring to what we imagine an agency had in mind.''
Post, at 4.  Rather, we defer to an interpretation which was
a necessary presupposition of the ICC's decision.  We
recognize the well-established rule that an agency's action
may not be upheld on grounds other than those relied on by
the agency.  SEC v. Chenery Corp., 318 U. S. 80, 88 (1943).
But the fact that the ICC did not in so many words articu-
late its interpretation of the word ``required'' does not mean
that we may not defer to that interpretation, since the only
reasonable reading of the agency's opinion, and the only
plausible explanation of the issues that the agency ad-
dressed after considering the factual submissions by all of
the parties, is that the ICC's decision was based on the
proffered interpretation.  Chenery does not require a
remand under those circumstances.  It is noteworthy in this
regard that neither party contends the ICC's decision was
not informed and governed by this statutory interpretation.
B&M's primary argument to the Court is that the word
required must mean necessary.  Brief for Respondent B&M
16, 22, 44.  But this, as we have said, is quite inconsistent
with the statutory presumption of need to which the ICC
gave effect.
  There is no dispute on this record that Amtrak intends to
use the condemned track for its Montrealer service.  Under
the ICC's view that use is sufficient to satisfy the statutory
command that the rail property be ``required for intercity
rail passenger service.''  This is a reasonable interpretation
and application of the RPSA.  And it ends the judicial
inquiry on this point.
  What we have said also answers Judge Ginsburg's
concern that the ICC must make specific findings regarding
Amtrak's actual need for the condemnation.  The contention
that such a finding was necessary, to implement the
statutory criterion that the property be ``required for
intercity rail passenger service,'' was the basis for Judge
Ginsburg's concurrence in the Court of Appeals.  286 U. S.
App. D.C., at 12, 911 F.2d, at 754.  That position, however,
appears to be based on the same interpretation of the word
``required'' as adopted by the Court of Appeals' majority,
and so is inconsistent with the ICC's interpretation.  The
ICC contends that the factual finding is not mandated.  It
argues that the structure of the statute, combined with the
presumption created by the statute of Amtrak's need for the
property sought, creates a strong inference that the statute
authorizes Amtrak to make a reasonable business judgment
that condemnation of the property is advisable.  We agree.
The ICC's oversight responsibility, exercised by enforcing
the ``required for intercity rail passenger service'' language
as interpreted by the agency, is limited to ensuring that the
condemned property will be used in Amtrak's rail opera-
tions.  The further determination of need is delegated to
Amtrak, unless the statutory presumption is rebutted; and
it is not rebutted here.  Indeed, as our discussion above
indicates, supra, at __, it seems to us that any other
interpretation may be inconsistent with the statutory
presumption of need.  In all events, the ICC's interpretation
is a reasonable one and we may not substitute a different
view.
  Arguing against the ICC's interpretation, B&M cites to us
cases such as United States v. Carmack, 329 U. S. 230, 243,
n. 13 (1946), which suggest that delegations of eminent
domain power to private entities are of a limited nature.
We do not believe that argument has any relevance here
because Amtrak does not exercise eminent domain power
under 562(d).  Rather, the statute gives that power to the
ICC, a Government agency.  To be sure, the statute creates
a presumption in favor of conveyance to Amtrak.  But the
ICC must assess the impact of any condemnation and make
a determination as to just compensation.  Since 562(d) is
a proper exercise of regulatory authority, and the ICC's
oversight of Amtrak is intended to ensure compliance with
the statute, the eminent domain power here is not private.
  Furthermore, this case turns on the need for deference to
the ICC, not Amtrak.  There is nothing in the cases B&M
cites contradicting the rule of judicial deference to an
agency's statutory interpretation, even when the statute is
one authorizing condemnation of private property.  In short,
the principle advanced by B&M does not prevail over
Chevron's rule of deference.
  We also reject B&M's constitutional objections.  B&M
claims that 562(d) as interpreted by the agency violates
the ``public use'' requirement of the Fifth Amendment's
Takings Clause, because the transaction leaves unchanged
the use made by Amtrak of the condemned track.  B&M's
position cannot be reconciled with our precedents.  We have
held that the public use requirement of the Takings Clause
is coterminous with the regulatory power, and that the
Court will not strike down a condemnation on the basis
that it lacks a public use so long as the taking ``is rationally
related to a conceivable public purpose.''  Hawaii Housing
Authority v. Midkiff, 467 U. S. 229, 240-241 (1984); see also
Berman v. Parker, 348 U. S. 26, 32-34 (1954).  In Midkiff
we upheld land reform legislation which authorized
condemnations for the specific purpose of transferring
ownership to another private party, in order to eliminate a
land oligopoly.  In Berman we permitted land condemna-
tions which contemplated reselling the land to redevelopers,
as part of a plan to restore dilapidated sections of the
District of Columbia.  In both Midkiff and Berman, as in
the present case, condemnation resulted in the transfer of
ownership from one private party to another, with the basic
use of the property by the government remaining un-
changed.  The Court held these exercises of the condemna-
tion power to be constitutional, as long as the condemning
authorities were rational in their positions that some public
purpose was served.  Those holdings control here, for there
can be no serious argument that the ICC was irrational in
determining that the condemnation will serve a public
purpose, by facilitating Amtrak's rail service.  That suffices
to satisfy the Constitution, and we need not make a specific
factual determination as to whether the condemnation will
accomplish its objectives.  Midkiff, supra, at 242-243.
  As a last effort, B&M argues that this matter must be
remanded to the ICC because the agency did not make
adequate and accurate findings regarding several different
matters.  B&M claims that Amtrak failed to prove the
parties were ```unable' to agree'' on terms of sale.  In B&M's
view 562(d) demands that Amtrak engage in ``good faith
. . . negotiations'' before it may invoke its condemnation
powers.  Brief for Respondent B&M 42.  The ICC construed
the language of 562(d) in a more narrow fashion, to
mandate nothing more than a factual determination that
the parties will not be able to reach agreement through
further negotiations.  App. to Pet. for Cert. in No. 90-1419,
pp. 130a-131a (``Nothing in this record provides any
indication that Amtrak and B&M will ever reach agreement
on terms of sale'').  This is a reasonable interpretation of
the phrase ``unable to agree upon terms for the sale,'' and
we do not substitute a different view.  Thus the agency did
not err in concluding that this statutory prerequisite was
satisfied.
  B&M argues further that the ICC made inadequate
factual findings in concluding:  (1) that this conveyance will
not significantly impair B&M's ability to carry out its
obligations as a common carrier, 562(d)(1)(A), and (2) that
Amtrak's obligations cannot be met by the acquisition of
alternative property, 562(d)(1)(B).  As to significant
impairment, B&M's argument, like the decision of the Court
of Appeals on this point, 286 U. S. App. D.C., at 8-9, 911
F.2d, at 750-751, relies on the notion that in ang
impairment the ICC may consider only the conveyance
itself, not any mitigating measures adopted in response to
the conveyance such as the grant of trackage rights to
B&M.  We find no basis in the text or structure of 562(d)
for this position, and cannot say that the statute must be
interpreted to mandate such a restrictive inquiry.  The ICC
was not unreasonable in considering the effect of the
trackage rights agreements and the just compensation
award in assessing significant impairment; and the ICC's
conclusion, that B&M's ability to carry out its common
carrier obligations will not be impaired by the transaction
in any significant way, is supported by substantial evidence.
As to the availability of alternative property, the ICC
interpreted that provision as referring only to whether
Amtrak could provide service using an alternative route,
not whether a lesser interest in property would suffice to
meet Amtrak's needs.  Again, this was a reasonable reading
to which we defer.  Since B&M would have to prevail on
both the significant impairment and alternative property
issues to rebut Amtrak's presumption of need, there can be
no doubt that the ICC's finding that Amtrak established its
need for the property must be affirmed.
                           III
  For the reasons we have stated, we hold that the ICC did
not exceed its authority in ordering conveyance of the 48.8
mile segment of the Conn River Line from B&M to Amtrak.
Because of its contrary holding on this point, the Court of
Appeals did not address the parties' challenges to the ICC's
just compensation finding as well as certain other issues.
286 U. S. App. D.C., at 11, 911 F. 2d, at 753.  These
questions should be resolved on remand.  The judgment of
the Court of Appeals is reversed, and the case is remanded
for further proceedings consistent with this opinion.
                                      It is so ordered.
-------------------------------


SUPREME COURT OF THE UNITED STATES
                        --------
                Nos. 90-1419 and 90-1769
                        --------
        NATIONAL RAILROAD PASSENGER CORPORATION,
                   et al., PETITIONERS
90-1419                     v.
           BOSTON AND MAINE CORPORATION et al.

           INTERSTATE COMMERCE COMMISSION AND
               UNITED STATES, PETITIONERS
90-1769                     v.
           BOSTON AND MAINE CORPORATION et al.
  on writs of certiorari to the united states court of
      appeals for the district of columbia circuit
                    [March 25, 1992]

  Justice White, with whom Justice Blackmun and
Justice Thomas join, dissenting.
  The majority opinion proceeds from the well-established
principle that courts should defer to permissible agency
interpretations of ambiguous legislation.  Chevron U.S.A.
Inc. v. Natural Resources Defense Council, Inc., 467 U. S.
837, 843 (1984); Pauley v. Bethenergy Mines, Inc., 501 U. S.
___, ___ (1991).  I have no quarrel with that general
proposition.  I do, however, object to its invocation to justify
the majority's deference, not to an agency interpretation of
a statute, but to the post hoc rationalization of government
lawyers attempting to explain a gap in the reasoning and
factfinding of the Interstate Commerce Commission (ICC or
Commission).  Motor Vehicle Mfrs. Assn. of United States,
Inc. v. State Farm Mut. Automobile Ins. Co., 463 U. S. 29,
50 (1983).
  Section 402(d) of the Rail Passenger Service Act (RPSA),
codified at 45 U. S. C. 562(d), provides that Amtrak may
apply to the ICC for an order directing the conveyance of
another railroad's property if Amtrak can meet two condi-
tions:  Amtrak and the other railroad must be unable to
agree upon terms for sale of the property, and the property
must be ``required for intercity rail passenger service.''  If
these conditions are met, ``the need of [Amtrak] for the
property shall be deemed to be established,'' and the other
railroad will be able to retain its property only if it can
rebut the strong presumption of Amtrak's need.  Ibid.
  Because conferring upon Amtrak the presumption of need
will determine the outcome of most disputes under this
section, the two conditions that Amtrak must establish to
receive the benefit of the presumption assume particular
importance.  However, in the present case, the ICC failed
to address one of these factors.  Although the Commission
determined that the parties had been unable to come to
terms for sale of the disputed property, see App. to Pet. for
Cert. in No. 90-1419, pp. 130a-131a, it neither interpreted
nor applied the second condition, that the property be
``required for intercity rail passenger service.''  Instead,
after rejecting respondent's argument that Amtrak could
restore Montrealer service by obtaining trackage rights or
an easement, the ICC simply concluded that ``Amtrak has
demonstrated sufficient reason to justify acquisition of
ownership of the line.''  Id., at 43a.
  The majority acknowledges that ``the ICC's opinion is not
explicit in all of its details,'' see ante, at 9, but nevertheless
concludes that the Commission's reading of the statute is
entitled to deference because it ``gave effect to the statutory
presumption of Amtrak's `need' for the track, and in so
doing implemented and interpreted the statute in a manner
that comports with its words and structure.''  Ibid.  But this
begs the question of what showing Amtrak must make to
establish that the track is ``required'' so that Amtrak may
therefore obtain the benefit of the presumption of need.
  The simple fact is that the ICC never addressed this point,
and therefore failed to construe a key portion of the statute.
The omission is particularly significant because this is the
first case treating Amtrak's condemnation powers under
402(d) of the Act; it will guide future adjudications.
  Rather than acknowledging the ICC's omission and
remanding for clarification and factfinding, the majority
relies on the Government's argument that the Commission
must have interpreted the word ``required'' as meaning
``useful or appropriate.''  Ibid.  But this interpretation was
not developed by the ICC during its administrative proceed-
ings.  Indeed, the explanation was not even proposed in the
Commission's argument to the Court of Appeals.  This ICC
definition of ``required'' debuted in the Commission's briefs
before this Court.  It is nothing more than a creation of
appellate counsel, concocted to fill the gaps in the Commis-
sion's analysis.  ``The short-and sufficient-answer to [this]
submission is that the courts may not accept appellate
counsel's post hoc rationalizations for agency action. . . . It
is well established that an agency's action must be upheld,
if at all, on the basis articulated by the agency itself.''
Motor Vehicle Mfrs. Assn., supra, at 50 (emphasis added),
citing Burlington Truck Lines, Inc. v. United States, 371
U. S. 156, 168 (1962); SEC v. Chenery Corp., 332 U. S. 194,
196-197 (1947); American Textile Mfrs. Institute, Inc. v.
Donovan, 452 U. S. 490, 539 (1981).  Therefore, the majori-
ty is simply wrong in asserting that, even though ``the ICC
did not in so many words articulate its interpretation of the
word `required,''' the Court may nevertheless defer to the
Commission's decision.  See ante, at 11 (emphasis added).
  Because of the gap in the ICC's interpretation of the
statute, ``[t]here are no findings and no analysis here to
justify the choice made, no indication of the basis on which
the Commission exercised its expert discretion.''  Burlington
Truck Lines, Inc., supra, at 167.  The majority concludes,
again based on the agency's presumed interpretation of the
statute, that the Commission was not obligated to make
specific findings as to whether the property was ``required
for intercity rail passenger service.''  See ante, at 12.  This
magnifies the ICC's mistake; an administrative ``agency
must make findings that support its decision, and those
findings must be supported by substantial evidence.''
Burlington Truck Lines, Inc., 371 U. S., at 168.
  Deferring to a federal agency's construction of the
legislation that it is charged with administering is one
thing.  But deferring to inferences derived from reading
between the lines of an agency decision or excerpted from
the brief of a government lawyer is another matter entirely.
``For the courts to substitute their or counsel's discretion for
that of the Commission is incompatible with the orderly
functioning of the process of judicial review.''  Id., at 169.
Because the ICC has failed to provide a clear, authoritative
construction of ``required for intercity rail passenger
service,'' we should return this case to the Commission so
that the agency can do its job properly.  But we should not
strain the Chevron principle by deferring to what we
imagine an agency had in mind when it applied a statute.
Therefore, I respectfully dissent.
-------------------------------
