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                                                                   EXHIBIT 10.12

                            SECOND AMENDMENT TO THIRD
                      AMENDED AND RESTATED CREDIT AGREEMENT


         THIS SECOND AMENDMENT TO THIRD AMENDED AND RESTATED CREDIT AGREEMENT
(this "Second Amendment"), dated as of October 4, 2002, by and among the lenders
listed on the signature pages hereof (the "Lenders"), DYNAMEX INC., a Delaware
corporation (the "Borrower"), DYNAMEX OPERATIONS EAST, INC., a Delaware
corporation, DYNAMEX OPERATIONS WEST, INC., a Delaware corporation, ROAD RUNNER
TRANSPORTATION, INC., a Minnesota corporation, NEW YORK DOCUMENT EXCHANGE
CORPORATION, a New York corporation, DYNAMEX DEDICATED FLEET SERVICES, INC., a
Delaware corporation, DYNAMEX CANADA HOLDINGS, INC., a Delaware corporation,
DYNAMEX PROVINCIAL COURIERS, INC., a Delaware corporation, DYNAMEX CANADA
HOLDINGS NS CORP., a Nova Scotia (Canada) unlimited liability company, DYNAMEX
PROVINCIAL COURIERS NS CORP., a Nova Scotia (Canada) unlimited liability
company, DYNAMEX CANADA LIMITED PARTNERSHIP, a Nova Scotia (Canada) limited
partnership, DYNAMEX CANADA CORP., a Nova Scotia (Canada) unlimited liability
company, ALPINE ENTERPRISES LTD., a Manitoba (Canada) corporation, BANK OF
AMERICA, N.A., as administrative agent for itself and the other Lenders (in such
capacity, the "Administrative Agent"), and BANK ONE, NA, as syndication agent
under the Credit Agreement (in such capacity, the "Syndication Agent").

                                   BACKGROUND

         A. The Borrower, the other Loan Parties (as defined in the Credit
Agreement defined below), the Lenders, the Syndication Agent, and the
Administrative Agent are parties to that certain Third Amended and Restated
Credit Agreement, dated as of November 9, 2001, as amended by that certain First
Amendment to Third Amended and Restated Credit Agreement (said Third Amended and
Restated Credit Agreement, the "Credit Agreement"; the terms defined in the
Credit Agreement and not otherwise defined herein shall be used herein as
defined in the Credit Agreement).

         B. The Borrower, the Lenders, the Syndication Agent and the
Administrative Agent desire to amend the Credit Agreement.

         NOW, THEREFORE, in consideration of the covenants, conditions and
agreements hereafter set forth, and for other good and valuable consideration,
the receipt and adequacy of which are all hereby acknowledged, the parties
hereto covenant and agree as follows:

         1. AMENDMENT. Section 10.2 of the Credit Agreement is hereby amended to
read as follows:

                  Section 10.2 Minimum Net Worth. The Borrower and its
         consolidated Subsidiaries will at all times maintain Net Worth in an
         amount equal to not less than the sum of (a) (i) prior to the time when
         the settlement of the Shareholder Litigation has been consummated,
         $38,500,000 or (ii) on and after the time when the settlement of the
         Shareholder Litigation has been consummated (which

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         settlement involves the issuance of additional Capital Stock of the
         Borrower), $40,000,000, plus (b) 75% of cumulative Net Income, if
         positive for any fiscal quarter (i.e., exclusive of any negative Net
         Income for any fiscal quarter), for any fiscal quarter commencing on
         and after August 1, 2001, plus (c) all Net Proceeds of each Equity
         Issuance which occurs on or after January 1, 2001.

         2. REPRESENTATIONS AND WARRANTIES TRUE; NO EVENT OF DEFAULT. By its
execution and delivery hereof, the Borrower represents and warrants that, as of
the date hereof, after taking into account the effectiveness of this Second
Amendment:

         (a) the representations and warranties contained in the Credit
Agreement and the other Loan Documents are true and correct on and as of the
date hereof as made on and as of such date; and

         (b) no event has occurred and is continuing which constitutes a Default
or an Event of Default.

         3. CONDITIONS OF EFFECTIVENESS. This Second Amendment shall be
effective upon satisfaction of the following conditions:

         (a) the representations and warranties set forth in Section 2 of this
Second Amendment shall be true and correct;

         (b) the Administrative Agent shall have received counterparts of this
Second Amendment executed by the Required Lenders;

         (c) the Administrative Agent shall have received counterparts of this
Second Amendment executed by the Borrower and acknowledged by each Loan Party;
and

         (d) the Administrative Agent shall have received in form and substance
satisfactory to the Administrative Agent, such other documents, certificates and
instruments as the Lenders shall require.

         4. LOAN PARTY'S ACKNOWLEDGMENT. By signing below, each Loan Party (i)
acknowledges, consents and agrees to the execution, delivery and performance by
the Borrower of this Second Amendment, (ii) acknowledges and agrees that its
obligations in respect of the Loan Documents to which it is a party are not
released, diminished, waived, modified, impaired or affected in any manner by
this Second Amendment, or any of the provisions contemplated herein, (iii)
ratifies and confirms its obligations under the Loan Documents to which it is a
party, and (iv) acknowledges and agrees that it has no claim or offsets against,
or defenses or counterclaims to, its obligations under the Loan Documents to
which it is a party.

         5. RELEASE. IN CONSIDERATION OF THE LENDER'S EXECUTION OF THIS SECOND
AMENDMENT, EACH OF THE LOAN PARTIES, IN EACH CASE ON BEHALF OF ITSELF AND EACH
OF THEIR SUCCESSORS AND ASSIGNS (COLLECTIVELY, THE "RELEASORS"), DOES
VOLUNTARILY AND KNOWINGLY RELEASE AND FOREVER DISCHARGE EACH LENDER AND
ADMINISTRATIVE AGENT AND THEIR RESPECTIVE PREDECESSORS, OFFICERS, DIRECTORS,


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EMPLOYEES, AGENTS, SUCCESSORS AND ASSIGNS (EACH, A "RELEASED PARTY") FROM ALL
POSSIBLE CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES,
AND LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR UNANTICIPATED,
SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT LAW OR IN
EQUITY, ARISING ON OR BEFORE THE DATE THIS SECOND AMENDMENT IS EXECUTED, WHICH
BORROWER OR ANY LOAN PARTY MAY NOW HAVE AGAINST ANY RELEASED PARTY, IF ANY, AND
IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS ARISE OUT OF CONTRACT, TORT, VIOLATION
OF LAW OR REGULATIONS, OR OTHERWISE, AND ARISING FROM ANY "OBLIGATIONS",
INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING FOR, CHARGING, TAKING, RESERVING,
COLLECTING OR RECEIVING INTEREST IN EXCESS OF THE HIGHEST LAWFUL RATE
APPLICABLE, THE EXERCISE OF ANY RIGHTS AND REMEDIES UNDER THE CREDIT AGREEMENT
OR OTHER LOAN DOCUMENTS, AND NEGOTIATION FOR AND EXECUTION OF THIS SECOND
AMENDMENT.

         6. REFERENCE TO THE CREDIT AGREEMENT.

         (a) Upon and during the effectiveness of this Second Amendment, each
reference in the Credit Agreement to "this Agreement", "hereunder", or words of
like import shall mean and be a reference to the Credit Agreement, as affected
by this Second Amendment.

         (b) Except as expressly set forth herein, this Second Amendment shall
not by implication or otherwise limit, impair, constitute a waiver of, or
otherwise affect the rights or remedies of the Administrative Agent or the
Lenders under the Credit Agreement or any of the other Loan Documents, and shall
not alter, modify, amend, or in any way affect the terms, conditions,
obligations, covenants, or agreements contained in the Credit Agreement or the
other Loan Documents, all of which are hereby ratified and affirmed in all
respects and shall continue in full force and effect.

         7. COSTS AND EXPENSES. The Borrower shall be obligated to pay the costs
and expenses of the Administrative Agent in connection with the preparation,
reproduction, execution and delivery of this Second Amendment and the other
instruments and documents to be delivered hereunder.

         8. EXECUTION IN COUNTERPARTS. This Second Amendment may be executed in
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed to be
an original and all of which when taken together shall constitute but one and
the same instrument. For purposes of this Second Amendment, a counterpart hereof
(or signature page thereto) signed and transmitted by any Person party hereto to
the Administrative Agent (or its counsel) by facsimile machine, telecopier or
electronic mail is to be treated as an original. The signature of such Person
thereon, for purposes hereof, is to be considered as an original signature, and
the counterpart (or signature page thereto) so transmitted is to be considered
to have the same binding effect as an original signature on an original
document.


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         9. GOVERNING LAW; BINDING EFFECT. This Second Amendment shall be
governed by and construed in accordance with the laws of the State of Texas
(without giving effect to conflict of laws) and the United States of America,
and shall be binding upon the Borrower and each Lender and their respective
successors and assigns.

         10. HEADINGS. Section headings in this Second Amendment are included
herein for convenience of reference only and shall not constitute a part of this
Second Amendment for any other purpose.

         11. ENTIRE AGREEMENT. THE CREDIT AGREEMENT, AS AMENDED BY THIS SECOND
AMENDMENT, AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN
THE PARTIES AS TO THE SUBJECT MATTER THEREIN AND HEREIN AND MAY NOT BE
CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL
AGREEMENTS BETWEEN THE PARTIES.

                   REMAINDER OF PAGE LEFT INTENTIONALLY BLANK


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IN WITNESS WHEREOF, the parties hereto have executed this Second Amendment as of
the date first above written.

                           DYNAMEX INC.



                           By:      /s/ Ray Schmitz
                                    --------------------------------------------
                                    Ray E. Schmitz
                                    Vice President & Chief Financial Officer


                           DYNAMEX OPERATIONS EAST, INC.
                           DYNAMEX OPERATIONS WEST, INC.
                           ROAD RUNNER TRANSPORTATION, INC.
                           NEW YORK DOCUMENT EXCHANGE CORPORATION
                           DYNAMEX DEDICATED FLEET SERVICES, INC.
                           DYNAMEX CANADA HOLDINGS, INC.
                           DYNAMEX PROVINCIAL COURIERS, INC.
                           DYNAMEX CANADA HOLDINGS NS         CORP.
                           DYNAMEX PROVINCIAL COURIERS NS CORP.
                           DYNAMEX CANADA LIMITED PARTNERSHIP
                           DYNAMEX CANADA CORP.
                           ALPINE ENTERPRISES LTD.



                           By:      /s/ Ray Schmitz
                                    --------------------------------------------
                                    Ray E. Schmitz
                                    Vice President and Chief Financial Officer


                           ADMINISTRATIVE AGENT:

                           BANK OF AMERICA, N.A.,
                           as Administrative Agent



                           By:      /s/ Suzanne M. Paul
                                    --------------------------------------------
                                    Name:    Suzanne M. Paul
                                    Title:   Vice President


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                           LENDERS:

                           BANK OF AMERICA, N.A.



                           By:      /s/ Michael F. Murray
                                    --------------------------------------------
                                    Name:    Michael F. Murray
                                    Title:   Vice President


                           BANK ONE, N.A., (Main Office Chicago)
                           as Syndication Agent and as a Lender



                           By:      /s/ Wyatt Dickson
                                    --------------------------------------------
                                    Name:    Wyatt Dickson
                                    Title:   First Vice President



                           THE BANK OF NOVA SCOTIA



                           By:      /s/ N. Bell
                                    --------------------------------------------
                                    Name:    N. Bell
                                    Title:   Senior Manager




                           FLEET NATIONAL BANK


                           By:      /s/ Kay H. Campbell
                                    --------------------------------------------
                                    Name:    Kay H. Campbell
                                    Title:   Authorized Officer


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                           BANK AUSTRIA CREDITANSTALT
                           CORPORATE FINANCE, INC.


                           By:
                                    ---------------------------------------
                                    Name:
                                           --------------------------------

                                    Title:
                                           --------------------------------



                           By:
                                    ---------------------------------------
                                    Name:
                                           --------------------------------

                                    Title:
                                           --------------------------------


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