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Exhibit 10.16

Execution Copy

SIXTH AMENDMENT TO CREDIT AGREEMENT

        This SIXTH AMENDMENT TO CREDIT AGREEMENT (this "Amendment"), made and
entered into as of January 14, 2002, is by and between Marten Transport, Ltd., a
Delaware corporation (the "Borrower"), the banks which are signatories to the
Credit Agreement described below (the "Banks") and U.S. Bank National
Association, a national banking association, as agent for the Banks (in such
capacity, the "Agent").

RECITALS

        1.    The Agent, the Banks and the Borrower entered into a Credit
Agreement dated as of October 30, 1998 as amended by a First Amendment dated as
of January 3, 2000, a Second Amendment dated as of January 19, 2000, a Third
Amendment dated as of April 5, 2000, a Fourth Amendment dated as of May 31, 2000
and a Fifth Amendment dated as of December 6, 2000 (as amended, the "Credit
Agreement"); and

        2.    The Borrower desires to amend certain provisions of the Credit
Agreement, and the Agent and the Banks have agreed to make such amendments,
subject to the terms and conditions set forth in this Amendment.

AGREEMENT

        NOW, THEREFORE, for good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, the parties hereto hereby covenant
and agree to be bound as follows:

        Section 1.    Capitalized Terms.    Capitalized terms used herein and
not otherwise defined herein shall have the meanings assigned to them in the
Credit Agreement, unless the context shall otherwise require.

        Section 2.    Amendments.    The Credit Agreement is hereby amended as
follows:

        2.1    Definitions.    The definition of "Eurodollar Rate" contained in
Section 1.1 of the Credit Agreement is amended to read in its entirety as
follows:

        "Eurodollar Rate": With respect to each Interest Period applicable to a
Eurodollar Rate Advance, the average offered rate for deposits in United States
dollars (rounded upward, if necessary, to the nearest 1/16 of 1%) for delivery
of such deposits on the first day of such Interest Period, for the number of
days in such Interest Period, which appears on Telerate page 3750 as of
11:00 AM, London time (or such other time as of which such rate appears) two
Eurodollar Business Days prior to the first day of such Interest Period, or the
rate for such deposits determined by the Agent at such time based on such other
published service of general application as shall be selected by the Agent for
such purpose; provided, that in lieu of determining the rate in the foregoing
manner, the Agent may determine the rate based on rates at which United States
dollar deposits are offered to the Agent in the interbank Eurodollar market at
such time for delivery in Immediately Available Funds on the first day of such
Interest Period in an amount approximately equal to the Advance by the Agent to
which such Interest Period is to apply (rounded upward, if necessary, to the
nearest 1/16 of 1%). "Telerate page 3750" means the display designated as such
on the Telerate reporting system operated by Telerate System Incorporated (or
such other page as may replace page 3750 for the purpose of displaying London
interbank offered rates of major banks for United States dollar deposits).

        Section 1.1 of the Credit Agreement is further amended by deleting the
definitions of "Reference Rate" and "Reference Rate Advance" in their
entireties.

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        Section 1.1 of the Credit Agreement is further amended by adding the
definitions of "Prime Rate" and "Prime Rate Advance" thereto in correct
alphabetical order:

        "Prime Rate": The rate of interest from time to time publicly announced
by the Agent as its "prime rate." The Agent may lend to its customers at rates
that are at, above or below the Prime Rate. For purposes of determining any
interest rate hereunder or under any other Loan Document which is based on the
Prime Rate, such interest rate shall change as and when the Prime Rate shall
change.

        "Prime Rate Advance": An Advance with respect to which the interest rate
is determined by reference to the Prime Rate.

        2.2    Conversions and Continuations.    The penultimate sentence of
Section 2.4 of the Credit Agreement is deleted in its entirety and the following
is substituted in lieu thereof:

If the Borrower shall fail to notify the Agent of the continuation of any
Eurodollar Rate Advances within the time required by this Section, at the option
of the Agent, such Advances shall, on the last day of the Interest Period
applicable thereto (A) automatically be continued as Eurodollar Rate Advances of
the same type and the same Interest Period or (B) automatically be converted to
Prime Rate Advances.

        2.3    Prime Rate.    Except for references to such terms specifically
so amended by this Amendment, all remaining references to the term "Reference
Rate" or "Reference Rate Advance" contained in the Credit Agreement are hereby
amended to be references to the term "Prime Rate" or "Prime Rate Advance," as
applicable.

        2.4    Investments.    Section 6.12 of the Credit Agreement is hereby
amended to add Section 6.12(j) as follows:

        6.12(j).    Investments in MW Logistics, LLC, in the form of revolving
debt or equity interests, not to exceed, in the aggregate, $3,000,000.

        Section 3.    Effectiveness of Amendments.    The amendments contained
in this Amendment shall become effective upon delivery by the Borrower of, and
compliance by the Borrower with, the following:

        3.1  This Amendment duly executed by the Borrower.

        3.2  A copy of the resolutions of the Board of Directors of the Borrower
authorizing the execution, delivery and performance of this Amendment certified
as true and accurate by its Secretary or Assistant Secretary, along with a
certification by such Secretary or Assistant Secretary (i) certifying that there
has been no amendment to the Certificate of Incorporation or Bylaws of the
Borrower since true and accurate copies of the same were delivered to the Agent
with a certificate of the Secretary of the Borrower dated October 30, 1998, and
(ii) identifying each officer of the Borrower authorized to execute this
Amendment and any other instrument or agreement executed by the Borrower in
connection with this Amendment (collectively, the "Amendment Documents"), and
certifying as to specimens of such officer's signature and such officer's
incumbency in such offices as such officer holds.

        3.3  Certified copies of all documents evidencing any necessary
corporate action, consent or governmental or regulatory approval (if any) with
respect to this Amendment.

        3.4  The Borrower shall have satisfied such other conditions as
specified by the Agent and the Banks, including payment of all unpaid legal fees
and expenses incurred by the Agent through the date of this Amendment in
connection with the Credit Agreement and the Amendment Documents.

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        Section 4.    Representations, Warranties, Authority, No Adverse
Claim.    

        4.1    Reassertion of Representations and Warranties, No Default.    The
Borrower hereby represents that on and as of the date hereof and after giving
effect to this Amendment (a) all of the representations and warranties contained
in the Credit Agreement are true, correct and complete in all respects as of the
date hereof as though made on and as of such date, except for changes permitted
by the terms of the Credit Agreement, and (b) there will exist no Default or
Event of Default under the Credit Agreement as amended by this Amendment on such
date which has not been waived by the Banks.

        4.2    Authority, No Conflict, No Consent Required.    The Borrower
represents and warrants that the Borrower has the power and legal right and
authority to enter into the Amendment Documents and has duly authorized as
appropriate the execution and delivery of the Amendment Documents and other
agreements and documents executed and delivered by the Borrower in connection
herewith or therewith by proper corporate action, and none of the Amendment
Documents nor the agreements contained herein or therein contravenes or
constitutes a default under any agreement, instrument or indenture to which the
Borrower is a party or a signatory or a provision of the Borrower's Certificate
of Incorporation, Bylaws or any other agreement or requirement of law, or result
in the imposition of any Lien on any of its property under any agreement binding
on or applicable to the Borrower or any of its property except, if any, in favor
of the Agent. The Borrower represents and warrants that no consent, approval or
authorization of or registration or declaration with any Person, including but
not limited to any governmental authority, is required in connection with the
execution and delivery by the Borrower of the Amendment Documents or other
agreements and documents executed and delivered by the Borrower in connection
therewith or the performance of obligations of the Borrower therein described,
except for those which the Borrower has obtained or provided and as to which the
Borrower has delivered certified copies of documents evidencing each such action
to the Agent.

        4.3    No Adverse Claim.    The Borrower warrants, acknowledges and
agrees that no events have been taken place and no circumstances exist at the
date hereof which would give the Borrower a basis to assert a defense, offset or
counterclaim to any claim of the Agent or the Banks with respect to the
Obligations.

        Section 5.    Affirmation of Credit Agreement, Further
References.    The Agent, the Banks and the Borrower each acknowledge and affirm
that the Credit Agreement, as hereby amended, is hereby ratified and confirmed
in all respects and all terms, conditions and provisions of the Credit
Agreement, except as amended by this Amendment, shall remain unmodified and in
full force and effect. All references in any document or instrument to the
Credit Agreement are hereby amended and shall refer to the Credit Agreement as
amended by this Amendment. All of the terms, conditions, provisions, agreements,
requirements, promises, obligations, duties, covenants and representations of
the Borrower under such documents and any and all other documents and agreements
entered into with respect to the obligations under the Credit Agreement are
incorporated herein by reference and are hereby ratified and affirmed in all
respects by the Borrower.

        Section 6.    Merger and Integration, Superseding Effect.    This
Amendment, from and after the date hereof, embodies the entire agreement and
understanding between the parties hereto and supersedes and has merged into this
Amendment all prior oral and written agreements on the same subjects by and
between the parties hereto with the effect that this Amendment, shall control
with respect to the specific subjects hereof and thereof.

        Section 7.    Severability.    Whenever possible, each provision of this
Amendment and the other Amendment Documents and any other statement, instrument
or transaction contemplated hereby

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or thereby or relating hereto or thereto shall be interpreted in such manner as
to be effective, valid and enforceable under the applicable law of any
jurisdiction, but, if any provision of this Amendment, the other Amendment
Documents or any other statement, instrument or transaction contemplated hereby
or thereby or relating hereto or thereto shall be held to be prohibited, invalid
or unenforceable under the applicable law, such provision shall be ineffective
in such jurisdiction only to the extent of such prohibition, invalidity or
unenforceability, without invalidating or rendering unenforceable the remainder
of such provision or the remaining provisions of this Amendment, the other
Amendment Documents or any other statement, instrument or transaction
contemplated hereby or thereby or relating hereto or thereto in such
jurisdiction, or affecting the effectiveness, validity or enforceability of such
provision in any other jurisdiction.

        Section 8.    Successors.    The Amendment Documents shall be binding
upon the Borrower, the Agent and the Banks and their respective successors and
assigns, and shall inure to the benefit of the Borrower, the Agent and the Banks
and the successors and assigns of the Agent and the Banks.

        Section 9.    Legal Expenses.    As provided in Section 9.2 of the
Credit Agreement, the Borrower agrees to reimburse the Agent and the Banks, upon
execution of this Amendment, for all reasonable out-of-pocket expenses
(including attorney' fees and legal expenses of Dorsey & Whitney LLP, counsel
for the Agent) incurred in connection with the Credit Agreement, including in
connection with the negotiation, preparation and execution of the Amendment
Documents and all other documents negotiated, prepared and executed in
connection with the Amendment Documents, and in enforcing the obligations of the
Borrower under the Amendment Documents, and to pay and save the Agent and the
Banks harmless from all liability for, any stamp or other taxes which may be
payable with respect to the execution or delivery of the Amendment Documents,
which obligations of the Borrower shall survive any termination of the Credit
Agreement.

        Section 10.    Headings.    The headings of various sections of this
Amendment have been inserted for reference only and shall not be deemed to be a
part of this Amendment.

        Section 11.    Counterparts.    The Amendment Documents may be executed
in several counterparts as deemed necessary or convenient, each of which, when
so executed, shall be deemed an original, provided that all such counterparts
shall be regarded as one and the same document, and either party to the
Amendment Documents may execute any such agreement by executing a counterpart of
such agreement.

        Section 12.    Governing Law.    THE AMENDMENT DOCUMENTS SHALL BE
GOVERNED BY THE INTERNAL LAWS OF THE STATE OF MINNESOTA, WITHOUT GIVING EFFECT
TO CONFLICT OF LAW PRINCIPLES THEREOF, BUT GIVING EFFECT TO FEDERAL LAWS
APPLICABLE TO NATIONAL BANKS, THEIR HOLDING COMPANIES AND THEIR AFFILIATES.

        [THE REMAINDER OF THIS PAGE LEFT BLANK INTENTIONALLY.]

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        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed as of the date and year first above written.

BORROWER:   MARTEN TRANSPORT, LTD.
 
 
By:
 
/s/ Franklin J. Foster

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Title:
 
Vice President

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Revolving Commitment Amount:
$45,000,000
 
U.S. BANK NATIONAL ASSOCIATION,
In its individual corporate capacity and as Agent
 
 
By:
 
/s/ Michael J. Reymann

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Title:
 
Vice President

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Revolving Commitment Amount:
$15,000,000
 
THE NORTHERN TRUST COMPANY
 
 
By:
 
/s/ Jeffrey B. Clark

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Title:
 
Vice President

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QuickLinks

Exhibit 10.16

Execution Copy

SIXTH AMENDMENT TO CREDIT AGREEMENT
RECITALS
AGREEMENT