<PAGE>

                              FIRST AMENDMENT TO
                               CREDIT AGREEMENT
                               ----------------

     This First Amendment to Credit Agreement (this "Amendment") is dated as of
August 11, 1998 and entered into by and among  U.S. XPRESS ENTERPRISES, INC.(the
"Borrower"), the BANKS listed on the signature pages hereof (the "Lenders"),
WACHOVIA BANK, N.A., as Administrative Agent, NATIONSBANK, N.A., as Syndication
Agent, BANKBOSTON, N.A.,as Documentation Agent, and SUNTRUST BANK, CHATTANOOGA,
N.A., as Co-Agent.

                                 W I T N E S S E T H:
                                 -------------------

     WHEREAS, the parties hereto are parties to that certain Credit Agreement,
dated as of January 15, 1998 (the "Credit Agreement"); and

     WHEREAS, the Borrower has requested that the Lenders increase the
Commitments under the Credit Agreement, modify the provisions of the Credit
Agreement concerning  acquisitions, and make certain other changes in the Credit
Agreement;

     NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties hereto agree as follows:

     Section 1.  Amendments.   The terms of the Credit Agreement are hereby
     ---------   -----------
amended as follows:

     (a)    Definitions.  Section 1.1 of the Credit Agreement is amended by
            -----------
deleting therefrom the definitions of "Commitment" and "Commitment Share" and
adding thereto the following defined terms:

          "Commitment" means, with respect to each Bank, (i) the amount set
forth opposite the name of such Bank on the schedule below, and (ii) as to any
Bank which enters into any Assignment and Acceptance  (whether as transferor
Bank or as Assignee thereunder), the amount of such Bank's Commitment after
giving effect to such Assignment and Acceptance, in each case as such amount may
be reduced from time to time pursuant to Sections 2.07 and 2.08, and "Commitment
Share" means the percentage of the total Commitment set forth opposite the name
of such Bank on the schedule below, as such percentage may be adjusted from time
to time pursuant to Section 10.08(c):
<PAGE>

<TABLE>
<CAPTION>

Bank                                   Commitment        Commitment Share
----                                  ------------       -----------------
<S>                                   <C>                 <C>

Wachovia Bank, N.A.                   $ 33,750,000                15%

SunTrust Bank,
Chattanooga, N.A.                     $ 30,937,500             13.75%

NationsBank, N.A.                     $ 30,937,500             13.75%

BankBoston, N.A.                      $ 30,937,500             13.75%

AmSouth Bank                          $ 26,000,000             11.56%

Bank of America National
Trust & Savings Association           $ 17,437,500              7.75%

Chase Bank of Texas, National
Association,
f/k/a Texas Commerce Bank
National Association                  $ 17,437,500              7.75%

ABN-Amro Bank, N.A.                   $ 17,437,500              7.75%

First American National Bank          $ 11,687,500              5.19%

First Tennessee Bank, N.A.            $  8,437,500              3.75%

TOTAL COMMITMENT                      $225,000,000               100%

</TABLE>
     (b)  Representation and Warranty as to Year 2000 Compliance.  A new Section
          -------------------------------------------------------
5.19 is added to the Credit Agreement as follows:

          "Section 5.19.  Year 2000 Compliance.  The Borrower has (i) initiated
                          ---------------------
a review and assessment of all areas within its and each of its Subsidiaries'
business and operations (including those affected by suppliers and vendors) that
could be adversely affected by the "Year 2000 Problem" (that is, the risk that
computer applications used by the Borrower or any of its Subsidiaries (or its
suppliers and vendors) may be unable to recognize and perform properly date-
sensitive functions involving certain dates prior to and any date after December
31, 1999), (ii) developed a plan and timeline for addressing the Year 2000
Problem on a timely basis, and (iii) to date, implemented that plan in
accordance with that timetable.  The Borrower reasonably believes that all
computer applications (including those of its suppliers and vendors) that are
material to its or any of its Subsidiaries' business and operations will on a
timely basis be able to perform properly date-sensitive functions for all dates
before and after January 1, 2000 (that is,

                                       2
<PAGE>

be "Year 2000 compliant"), except to the extent that a failure to do so could
not reasonably be expected to have Material Adverse Effect."

     (c)  Limitation on Acquisitions.   Section 6.25(a) of the Credit Agreement
          ---------------------------
is deleted in its entirety and the following is substituted therefore:

          "(a) during calendar year 1998, the Borrower may acquire all of the
outstanding capital stock of Victory Express, Inc. and of PST Vans, Inc.,
provided that the acquisition of the capital stock of PST Vans, Inc. is on the
terms and conditions set forth in that certain Agreement and Plan of  Merger
dated as July 7, 1998, by and among PST Vans, Inc., U.S. Xpress Enterprises,
Inc., and PST Acquisition Corp., and further provided that for any Fiscal Year
thereafter the aggregate total consideration for all such acquisitions shall not
exceed $75,000,000."

     (d)  Covenant as to Year 2000 Compliance.  A new Section 6.27 is added to
          ------------------------------------
the Credit Agreement as follows:

          "Section 6.27.  Year 2000 Compliance.  The Borrower will promptly
                          --------------------
notify the Agent in the event the Borrower discovers or determines that any
computer application (including those of its suppliers and vendors) that is
material to its or any of its Subsidiaries' business and operations will not be
Year 2000 compliant on a timely basis, except to the extent that such failure
could not reasonably be expected to have a Material Adverse Effect."

     Section 2.  Replacement of Revolving Loan Notes.  The Revolving Loan Note
     ---------   ------------------------------------
previously delivered by the Borrower to each Lender shall be replaced by the
execution and delivery of an Amended Revolving Loan Note, in form and substance
as set forth on Exhibit A-1 hereto, which Amended Note shall reflect the
increased Commitment from each Lender to the Borrower.

     Section 3.  Conditions Precedent.  This First Amendment and the obligations
     ---------   ---------------------
of the Lenders evidenced hereunder shall not be effective until the
Administrative Agent shall have received each of the following documents, each
of which shall be satisfactory in form and substance to the Administrative
Agent:

          (a) The Amended Revolving Loan Notes complying with the terms of this
     Amendment, duly executed and delivered by the Borrower;

          (b) Certified copies of all necessary action taken by the Borrower to
     authorize the execution, delivery and performance of this Amendment and the
     Revolving Loan Notes;

          (c) Certificates of Incumbency and specimen signatures signed by the
     appropriate authenticating person with respect to each of the officers or
     other persons of the Borrower who are authorized to execute and deliver
     this Amendment and the Amended Revolving Loan Notes;

                                       3
<PAGE>

          (d) A Reaffirmation of Guaranty from each Subsidiary in substantially
     the form of Exhibit B-1 hereto;

          (e) A Certificate executed by the Chief Executive Officer or Chief
     Financial Officer of the Borrower stating that, to the best of his
     knowledge and based upon an examination sufficient to enable him to make an
     informed statement, (i) all of the representations and warranties made or
     deemed to be made under the Credit Agreement are materially true and
     correct as of the date of this First Amendment to Credit Agreement, and
     (ii) no Default or Event of Default exists;

          (f) A fully executed copy of the Agreement and Plan of Merger dated as
     July 7, 1998, by and among PST Vans, Inc., U.S. Xpress Enterprises, Inc.,
     and PST Acquisition Corp., certified by the Chief Executive Officer of the
     Borrower as being in full force and effect; and

          (g) The opinion of Miller & Martin, counsel to the Borrower, addressed
     to the Lenders and the Agents and in form and substance satisfactory to the
     Administrative Agent.

          Section 4.  Reference to and Effect on the Credit Agreement and
          ---------   ---------------------------------------------------
the Other Loan Documents.
-------------------------

          (a) On and after the date hereof, each reference in the Credit
Agreement to "this Agreement," "hereunder," "hereof," "herein" or words of like
import referring to the Credit Agreement, and each reference in the other Loan
Documents to the "Credit Agreement," "thereunder," "thereof" or words of like
import referring to the Credit Agreement shall mean and be a reference to the
Credit Agreement as amended hereby.

          (b) Except as specifically amended by this Amendment, the Credit
Agreement and the other Loan Documents shall remain in full force and effect and
are hereby ratified and confirmed.

          (c)  The execution, delivery and performance of this Amendment shall
not, except as expressly provided herein, constitute a waiver of any provision
of, or operate as a waiver of any right, power or remedy of the Administrative
Agent or any Lender under the Credit Agreement or any of the other Loan
Documents.

     Section 5.  Miscellaneous.
     ----------  --------------

          (a)  Section and Subsection Headings.   Section and Subsection
               --------------------------------
headings in this Amendment are included herein for convenience of reference only
and shall not constitute a part of this Amendment for any other purpose or be
given any substantive effect.

          (b)  Governing Law. This Amendment and the rights and obligations of
               --------------
the parties hereunder shall be governed by, and shall be construed and enforced
in accordance with, the laws of the State of Georgia.

                                       4
<PAGE>

          (c)  Counterparts; Effectiveness.  This Amendment may be executed in
               ----------------------------
any number of counterparts and by different parties hereto and separate
counterparts, each of which when so executed and delivered shall be deemed an
original, but all such counterparts taken together shall constitute but one and
the same instrument; signature pages may be detached from multiple separate
counterparts and attached to a single counterpart so that all signature pages
are physically attached to the same document.  This Amendment shall become
effective upon the execution of a counterpart hereof by the Borrower and the
Required Lenders and receipt by the Borrower and the Administrative Agent of
written or telephonic notification of such execution and authorization or
delivery thereof.

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their respective officers thereunto duly
authorized as of the date first above written.

                                 U.S. XPRESS ENTERPRISES, INC.


                                 By:
                                     --------------------------------------
                                 Title:


                                 WACHOVIA BANK, N.A.,
                                 as Lender and Administrative Agent


                                 By:
                                     --------------------------------------
                                 Title:

                                 By:
                                     --------------------------------------
                                 Title:


                                 NATIONSBANK, N.A.,
                                 as Lender and Syndication Agent


                                 By:
                                     --------------------------------------
                                 Title:

                                       5
<PAGE>

                                 BANKBOSTON, N.A.,
                                 as Lender and Documentation Agent


                                 By:
                                     --------------------------------------
                                 Title:

                                 By:
                                     --------------------------------------
                                 Title:


                                 SUNTRUST BANK, CHATTANOOGA, N.A.
                                 as Lender and Co-Agent

                                 By:
                                     --------------------------------------
                                 Title:


                                 AMSOUTH BANK

                                 By:
                                     --------------------------------------
                                 Title:


                                 CHASE BANK OF TEXAS, NATIONAL ASSOCIATION
                                 f/k/a Texas Commerce Bank National
                                 Association

                                 By:
                                     --------------------------------------
                                 Title:


                                 BANK OF AMERICA NATIONAL
                                 TRUST & SAVINGS ASSOCIATION

                                 By:
                                     --------------------------------------
                                 Title:

                                       6
<PAGE>

                                 ABN-AMRO BANK, N.A.

                                 By:
                                     --------------------------------------
                                 Title:


                                 FIRST AMERICAN NATIONAL BANK

                                 By:
                                     --------------------------------------
                                 Title:


                                 FIRST TENNESSEE BANK, N.A.

                                 By:
                                     --------------------------------------
                                 Title:



                   [Final signature page to First Amendment]

                                       7