Exhibit 10.6

WAIVER, SIXTH AMENDMENT TO AMENDED AND
RESTATED CREDIT AGREEMENT
AND REAFFIRMATION OF GUARANTIES

THIS
WAIVER, SIXTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT AND
REAFFIRMATION OF GUARANTIES, dated as of May 7, 2009 (this Sixth Amendment), is entered into by and
between Quixote Corporation, a Delaware corporation (the Borrower), whose address is 35 East Wacker
Drive, Chicago, Illinois 60601, and Quixote Transportation Safety, Inc.,
Transafe Corporation, Energy Absorption Systems, Inc., Energy Absorption
Systems (AL) LLC, Surface Systems, Inc., Nu-Metrics, Inc., and Highway
Information Systems, Inc., as Subsidiary Guarantors, (each being referred to
herein as a Guarantor and
collectively referred to herein as the Guarantors),
and Bank of America, N.A., a national banking association (the Lender), whose address is 135 South
LaSalle Street, Chicago, Illinois 60603.

RECITALS:

A.     
Borrower and Lender entered into that certain Amended and Restated Credit
Agreement, dated as of April 20, 2005 (the Original
Credit Agreement), as amended by that certain First Amendment to
Amended and Restated Credit Agreement and Reaffirmation of Guaranties dated as
of December 1, 2006, (the First Amendment),
that certain Second Amendment to Amended and Restated Credit Agreement and
Reaffirmation of Guaranties dated as of March 15, 2007 (the Second Amendment), that certain Third
Amendment to Amended and Restated Credit Agreement and Reaffirmation of
Guaranties dated as of November 7, 2007 (the Third
Amendment), that certain Fourth Amendment to Amended and Restated
Credit Agreement and Reaffirmation of Guaranties dated as of November 7, 2008
(the Fourth Amendment) and that
certain Waiver, Fifth Amendment to Amended and Restated Credit Agreement and
Reaffirmation of Guaranties dated as of February 9, 2009 (the Fifth Amendment, and together with the
Original Credit Agreement, the First Amendment, the Second Amendment, the Third
Amendment and the Fourth Amendment, the Credit
Agreement) pursuant to which Credit Agreement Lender has made a
Revolving Loan to Borrower evidenced by that certain Second Amended and
Restated Revolving Loan Note, dated as of February 9, 2009, in the maximum
principal amount of $15,000,000, executed by Borrower and made payable to the
order of Lender (the Revolving Note).

B.     
In connection with the Original Credit Agreement, the Guarantors executed and
delivered to Lender that certain Guaranty dated as of May 16, 2003 in favor of
Lender, as amended by that Reaffirmation and Amendment of Subsidiary Guaranty
dated as of April 20, 2005 (the Guaranty).

C.     
Borrower has failed to comply with Section 7.4(D) and 7.4(E) of the Credit
Agreement for the period ending March 31, 2009 (the Existing Defaults). Borrower has requested
that Lender waive the Existing Defaults and Lender has agreed to waive the
Existing Defaults on the terms and conditions set forth herein.

D.     
Borrower and the Guarantors have also requested, and Lender has agreed to, the
modification of certain terms contained in the Credit Agreement as set forth
herein, all pursuant to the terms and conditions hereinafter set forth herein.

NOW
THEREFORE, in consideration of the premises and other good and valuable consideration,
the receipt and adequacy of which are hereby acknowledged, Borrower, the
Guarantors and Lender hereby agree as follows:

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AGREEMENTS:

1.     
RECITALS. The foregoing Recitals are hereby made a part of this Sixth
Amendment.

2.     
DEFINITIONS. Capitalized words and phrases used herein without definition
shall have the respective meanings ascribed thereto in the Credit Agreement.

3.     
WAIVER. Subject to the terms hereof, Lender, hereby waives the Existing
Defaults. Lender and Borrower hereby agree that the foregoing waiver of the
Existing Defaults shall in no way be deemed to be a waiver or forbearance of
any other default, any Unmatured Default or any other Event of Default, whether
now existing or hereafter arising, under the Credit Agreement (whether
occurring before or after giving effect to this Sixth Amendment) or any other
Loan Document.

4.     
AMENDMENTS TO THE CREDIT AGREEMENT.

| |                                                                                                                                         
| | ----------------------------------------------------------------------------------------------------------------------------------------
| | 4.1     
  Section 1.1 of the Credit Agreement.                                                                                         
| |                                                                                                                                         
| | (a)     
  Section 1.1 of the Credit Agreement is hereby amended by adding the following
  definitions where alphabetically appropriate:

| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | Borrowing
  Base Amount shall mean:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | (a)     an
  amount equal to 80% of the net amount (after deduction of such reserves and
  allowances as the Lender deems proper and necessary) of the Eligible
  Accounts; plus                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | (b)     the
  lesser of (i) an amount equal to 50% of the lower of cost or market value
  (after deduction of such reserves and allowances as the Lender deems proper
  and necessary) of the Eligible Inventory, or (ii) Ten Million Dollars and
  00/100 ($10,000,000); plus                                                                                                                                                                                                                                                                                                                                                                                                                        
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | (c)     80%
  of the orderly liquidation value of machinery and equipment of Borrower and
  its Subsidiaries, plus 75% of the fair market value (as evidenced by
  an appraisal acceptable to Lender) of the real property of Borrower and
  Subsidiaries as pledged hereunder less the Curtailment Amount.                                                                                                                                                                                                                                                                                                                                                                                           
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | Curtailment
  Amount shall mean an amount equal to Three Million Five Hundred Twenty Five Thousand ($3,525,000) plus
  $75,000 on April 30, 2009 and on the 30th day of each month
  thereafter.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | Eligible
  Accounts shall mean those Accounts of the Borrower or any Subsidiary
  which meet the following requirements:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
| | (a)     is
  genuine in all respects and have arisen in the ordinary course of the
  Borrowers business from (i) the performance of services by the Borrower or
  the applicable Subsidiary, which services have been fully performed,
  acknowledged and accepted by the Account Debtor or (ii) the sale, license,
  assignment or lease of Goods by the Borrower, including C.O.D. sales, which Goods have been completed in accordance with the Account Debtor's specifications (if any) and delivered to and accepted by the Account Debtor, and the Borrower has possession of, or has delivered to the Lender at the Lender's request, shipping and delivery receipts evidencing such shipment;

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| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (b)     is
  subject to a perfected, first priority Lien in favor of the Lender and is not
  subject to any other assignment, claim or Lien;                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (c)     is
  the valid, legally enforceable and unconditional obligation of the Account
  Debtor with respect thereto, and is not subject to the fulfillment of any
  condition whatsoever or any counterclaim, credit (except as provided in
  subsection (h) of this definition), trade or volume discount, allowance,
  discount, rebate or adjustment by the Account Debtor with respect thereto, or
  to any claim by such Account Debtor denying liability thereunder in whole or
  in part and the Account Debtor has not refused to accept and/or has not
  returned or offered to return any of the Goods or services which are the
  subject of such Account;
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (d)     the
  Account Debtor with respect thereto is a resident or citizen of, and is
  located within, the United States, unless the sale of goods or services
  giving rise to such Account is on letter of credit, bankers acceptance or
  other credit support terms reasonably satisfactory to the Lender;                                                                                                                                                                                                                                                                                                                                                       
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (e)     it is
  not an Account arising from a sale on approval, sale or return,
  consignment, guaranteed sale or bill and hold, or are subject to any
  other repurchase or return agreement;                                                                                                                                                                                                                                                                                                                                                                                                                                                               
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (f)     it is
  not an Account with respect to which possession and/or control of the goods
  sold giving rise thereto is held, maintained or retained by the Borrower or
  any Subsidiary (or by any agent or custodian of the Borrower or any
  Subsidiary) for the account of, or subject to, further and/or future
  direction from the Account Debtor with respect thereto;                                                                                                                                                                                                                                                                                       
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (g)     it
  has not arisen out of contracts with the United States or any department,
  agency or instrumentality thereof, unless the Borrower has assigned its right
  to payment of such Account to the Lender pursuant to the Assignment of Claims
  Act of 1940, and evidence (satisfactory to the Lender) of such assignment has
  been delivered to the Lender;                                                                                                                                                                                                                                                                                                 
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (h)     if
  the Borrower maintains a credit limit for an Account Debtor, the aggregate
  dollar amount of Accounts due from such Account Debtor; including such
  Account, does not exceed such credit limit;                                                                                                                                                                                                                                                                                                                                                                                                                                                         

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| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (i)     if
  the Account is evidence by chattel paper or an instrument, the originals of
  such chattel paper or instrument shall have been endorsed and/or assigned and
  delivered to the bank or, in the case of electronic chattel paper, shall be
  in the control of the Lender, in each case in a manner satisfactory to the
  Lender;                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (j)     such
  Account is evidenced by an invoice delivered to the related Account Debtor
  and is not more than (i) sixty 60 days (except in the case of Energy
  Absorptions Systems, Inc., ninety (90) days), past the due date thereof; or
  (ii) ninety (90) days past the original invoice date thereof, in each case
  according to the original terms of sale;                                                                                                                                                                                                                                                                                                                                                                                                                                          
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (k)     it is
  not an Account with respect to an Account Debtor that is located in any
  jurisdiction which has adopted a statute or other requirement with respect to
  which any Person that obtains business from within such jurisdiction must
  file a notice of business activities report or make any other required
  filings in a timely manner in order to enforce its claims in such
  jurisdictions courts unless (i) such notice of business activities report
  has been duly and timely filed or the borrower or the applicable Subsidiary
  is exempt from filing such report and has provided the bank with satisfactory
  evidence of such exemption or (ii) the failure to make such filings may be
  cured retroactively by the Borrower or the applicable Subsidiary for a
  nominal fee;
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (l)     the
  Account Debtor with respect thereto is not the Borrower or an Affiliate of
  the Borrower;                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (m)     such
  Account does not arise out of a contract or order which, by its terms,
  forbids or makes void or unenforceable the assignment thereof by the Borrower
  or any Subsidiary to the Lender and is not unassignable to the Lender for any
  other reason;                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (n)     there
  is no bankruptcy, insolvency or liquidation proceeding pending by or against
  the Account Debtor with respect thereto, nor has the Account Debtor suspended
  business, made a general assignment for the benefit of creditors or failed to
  pay its debts generally as they come due, and/or no condition or event has
  occurred having a material adverse effect on the Account Debtor which would
  require the Accounts of such Account Debtor to be deemed uncollectible in
  accordance with GAAP;                                                                                                                                                                                                                                                                                     
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (o)     it is
  not owed by an Account Debtor with respect to which twenty five percent (25%)
  or more of the aggregate amount of outstanding Accounts owed at such time by
  such Account Debtor is classified as ineligible under clause (j) of this
  definition;                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
| | (p)     if
  the aggregate amount of all Accounts owed by the Account Debtor thereon
  exceeds twenty five percent (25%) of the aggregate amount of all Accounts at
  such time, then all Accounts owed by such Account Debtor in excess of such amount shall be deemed ineligible; and                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         

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| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (q)     it
  does not violate the negative covenants and does satisfy the affirmative
  covenants of the Borrower contained in this Agreement, and it is otherwise
  not unacceptable to the Lender for any other reason.                                                                                                                                                                                                                                                                                                                                  
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | An Account
  which is at any time an Eligible Account, but which subsequently fails to meet
  any of the foregoing requirements, shall forthwith cease to be an Eligible
  Account. Further, with respect to any Account, if the Lender at any time
  hereafter determines in its discretion that the prospect of payment or
  performance by the Account Debtor with respect thereto is materially impaired
  for any reason whatsoever, such Account shall cease to be an Eligible Account
  after notice of such determination is given to the Borrower.
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | Eligible
  Inventory shall mean all Inventory of the Borrower or any Subsidiary
  which meets each of the following requirements:                                                                                                                                                                                                                                                                                                                                                                                                                        
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (a)     it is
  subject to a perfected, first priority Lien in favor of the Lender and is not
  subject to any other assignment, claim or Lien;                                                                                                                                                                                                                                                                                                                                                                                                            
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (b)     it is
  salable and not slow-moving, obsolete or discontinued, as determined in the
  sole and absolute discretion of the Lender;                                                                                                                                                                                                                                                                                                                                                                                                                  
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (c)     it is
  in the possession and control of the Borrower or any Subsidiary and it is
  stored and held in facilities owned by the Borrower or any Subsidiary or, if
  such facilities are not so owned, the Lender is in possession of a Collateral
  Access Agreement with respect thereto;                                                                                                                                                                                                                                                          
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (d)     is
  not Inventory produced in violation of the Fair Labor Standards Act and/or
  subject to the so-called hot goods provisions contained in Title 29 U.S.C.
  215(a); and                                                                                                                                                                                                                                                                                                                                                                       
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (e)     it is
  not subject to any agreement or license which would restrict the Lenders
  ability to sell or otherwise dispose of such Inventory;                                                                                                                                                                                                                                                                                                                                                                                                        
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (f)     it is
  located in the United States or in any territory or possession of the United
  States that has adopted Article 9 of the Uniform Commercial Code;                                                                                                                                                                                                                                                                                                                                                                                           
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (g)     it is
  not in transit to the Borrower or any Subsidiary or held by the Borrower or
  any Subsidiary on consignment;                                                                                                                                                                                                                                                                                                                                                                                                                             
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
| | (h)     it is
  not work-in-progress Inventory;                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          

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| |                                                                                                                                                                                          
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (i)     it is
  not supply items, packaging or any other similar materials;                                                                                                              
| |                                                                                                                                                                                          
| | (j)     it is
  not identified to any purchase order or contract to the extent progress or
  advance payments are received with respect to such Inventory;                               
| |                                                                                                                                                                                          
| | (k)     it
  does not breach any of the representations, warranties or covenants
  pertaining to Inventory set forth in the Loan Documents; and                                          
| |                                                                                                                                                                                          
| | (l)     the
  Lender shall not have determined in its reasonable discretion that it is
  unacceptable due to age, type, category, quality, quantity and/or any other
  reason whatsoever.
| |                                                                                                                                                                                          
| | Inventory
  which is at any time Eligible Inventory but which subsequently fails to meet
  any one of the foregoing requirements, shall forthwith cease to be Eligible
  Inventory.      

| |                                                                                                                                                                       
| | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (b)     
  The definition of Revolving Loan Availability in Section 1.1 of the Credit
  Agreement is hereby deleted in its entirety and replaced with the following:

| |                                                                                                                                                                                                                                                                               
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | Revolving
  Loan Availability shall mean at any time, the lesser of (a) the
  Revolving Loan Commitment less the Revolving Credit Obligations outstanding
  at such time, or (b) the Borrowing Base Amount less the Revolving Credit
  Obligations outstanding at such time.

| |                                                                                                                                                             
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------
| | 4.2    
  Section 3.3(B) of the Credit Agreement. Section 3.3(B) of the Credit
  Agreement is hereby deleted it is entirety and replaced with the following:

| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (B)    issue (or amend) any Letter of Credit which has an expiration
  date later than the date which is the earlier of (x) one (1) year after the
  date of issuance thereof or (y) the Revolving Credit Termination Date; provided,
  that any Letter of Credit with a one-year term may provide for the renewal
  thereof for additional one-year periods; provided further, that, in
  the event any Letter of Credit has an expiration date beyond the Revolving
  Credit Termination Date, Borrower agrees that no later than five (5) days
  prior to the Revolving Credit Termination Date Borrower shall post collateral
  with the Lender, acceptable to the Lender in its sole discretion, in an
  amount equal to one hundred five percent (105%) of the face amount of such
  Letter of Credit.

| |                                                                                                                                                                                        
| | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | 4.3    
  Section 7.1(A) of the Credit Agreement. Section 7.1(a)(iii) of the
  Credit Agreement is hereby amended by deleting it in its entirety and
  replacing it with the following:

| |                                                                                                                                                                                                                                                                                                                                                                                                                                                      
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (iii)    Monthly Reports. As soon as practicable, and in any
  event, no later than the thirty (30) days after the end of each month, the
  consolidated and consolidating financial statement of Borrower and its
  Subsidiaries at the end of such period, including balance sheet, statement of income and such other information (including non-financial information) as the Lender may request, in reasonable detail, prepared by the Borrower.

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| | 
| | 

4.4     
Section 7.1(A)(v), (vi) and (vii) are hereby deleted in their entirety and
restated as follows:

| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (v)     Borrowing
  Base Certificate. The Borrower shall, within thirty (30) days after the
  end of each month, until the Collateral Release Date, deliver to the Lender a
  Borrowing Base Certificate in the form of Exhibit Q, attached hereto
  certified as accurate by the Borrower and acceptable to the Lender in its
  sole and absolute discretion; provided that this requirement shall expire
  upon Lenders acceptance of Borrowers Certificate of Compliance with the
  Release Covenants delivered in accordance with Section 7.1(J).
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (vi)     
  Aged Accounts Schedule. The Borrower shall, within thirty (30) days
  after the end of each month, deliver to the Lender an aged schedule of the
  Accounts of the Borrower, listing the name and amount due from each Account
  Debtor and showing the aggregate amounts due from (a) 0-30 days, (b) 31-60
  days, (c) 61-90 days and (d) more than 90 days, and certified as accurate by
  the Borrower.                                                                                                                                 
| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
| | (vii)    
  Inventory Reports. The Borrower shall, within thirty (30) days after
  the end of each month, deliver to the Lender an inventory report, certified
  as accurate by the Borrower, and within such time as the Lender may specify,
  such other schedules and reports as the Lender may require.                                                                                                                                                                                                                                            

4.5    
Section 7.4 of the Credit Agreement.

| |                                                                                                                     
| | --------------------------------------------------------------------------------------------------------------------
| | (a)      Section 7.4(C) of the Credit Agreement is
  hereby deleted in its entirety and replaced with the following:

| |                                                                                                                                                                                                       
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (C)     Minimum
  EBITDA. The Borrower and its consolidated Subsidiaries shall have EBITDA
  of at least Eight Hundred Fifty Thousand Dollars ($850,000) for the fiscal
  quarter ended June 30, 2009.

| |                                                                                                                        
| | -----------------------------------------------------------------------------------------------------------------------
| | (b)     
  Sections 7.4(D) and 7.4(E) are hereby deleted in their entirety and replaced
  with Intentionally Omitted.

4.6    
Exhibit Q of the Credit Agreement. Exhibit Q to the Credit Agreement is
hereby deleted in its entirety and replaced with Exhibit A attached
hereto.

5.      
REAFFIRMATION OF GUARANTIES. Each of the Guarantors hereby expressly
(a) consents to the execution by Borrower and Lender of this Sixth
Amendment, (b) acknowledges that the Guaranteed Debt (as defined in each
of the Guaranties) includes all of the obligations and liabilities owing from
Borrower to Lender, including, but not limited to, the obligations and
liabilities of Borrower to Lender under and pursuant to the Credit Agreement, as amended from time to time, and as evidenced by the Revolving Note, as modified, extended and/or replaced from time to time, (c) reaffirms, assumes and binds themselves in all respects to all of the obligations, liabilities, duties, covenants, terms and conditions that are contained in their respective Guaranty, (d) agrees that all such obligations and liabilities under their respective Guaranty shall continue in full force and effect and shall not be discharged, limited, impaired or affected in any manner whatsoever, and (e) represents and warrants that each of the representations and warranties made by such Guarantor in any of the documents executed in connection with the Loans remain true and correct as of the date hereof.

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6.     
REPRESENTATIONS AND WARRANTIES. To induce Lender to enter into this Sixth
Amendment, Borrower and each Guarantor hereby certifies, represents and
warrants to Lender that:

6.1    
Organization. Borrower and each Guarantor is a corporation or a limited
liability company duly organized, existing and in good standing under the laws
of its state or organization with full and adequate corporate or limited
liability power, as the case may be, to carry on and conduct its business as
presently conducted. Borrower and each Guarantor is duly licensed or qualified
in all foreign jurisdictions wherein the nature of its activities require such
qualification or licensing. The Articles of Incorporation or Organization, as
the case may be, Bylaws (other than an amendment to the By-laws of Borrower
dated July 24, 2008) or Operating Agreement, as the case may be, Resolutions
and Incumbency Certificate of Borrower and each Guarantor have not been changed
or amended since the certified copies thereof were delivered to Lender in
connection with the Original Credit Agreement and the First Amendment. The
state issued organizational identification number for Borrower and each
Guarantor is listed on Schedule I hereto. The exact legal name of
Borrower and each Guarantor is as set forth in the preamble of this Sixth
Amendment, and neither Borrower nor any Guarantor currently conducts, nor has
it during the last five (5) years conducted, business under any other name or
trade name. Neither Borrower nor any Guarantor will change its name, its
organizational identification number, if it has one, its type of organization,
its jurisdiction of organization or other legal structure.

6.2   
Authorization. Borrower and each Guarantor is duly authorized to execute
and deliver this Sixth Amendment and Borrower is and will continue to be duly
authorized to borrow monies under the Credit Agreement, as amended hereby, and
to perform its obligations under the Credit Agreement, as amended hereby.

6.3    
No Conflicts. The execution and delivery of this Sixth Amendment and the
performance by Borrower and each Guarantor of its obligations under the Credit
Agreement, as amended hereby, do not and will not conflict with any provision
of law or of the articles of incorporation or bylaws of Borrower or any
Guarantor or of any agreement binding upon Borrower or any Guarantor.

6.4    
Validity and Binding Effect. The Credit Agreement, as amended hereby, is
a legal, valid and binding obligation of Borrower and each Guarantor,
enforceable against Borrower and each Guarantor in accordance with its terms,
except as enforceability may be limited by bankruptcy, insolvency or other
similar laws of general application affecting the enforcement of creditors
rights or by general principles of equity limiting the availability of
equitable remedies.

6.5    
Compliance with Credit Agreement. The representation and warranties set
forth in Section VI of the Credit Agreement, as amended hereby, are true and
correct with the same effect as if such representations and warranties had been
made on the date hereof, with the exception that
all references to the financial statements shall mean the financial statements
most recently delivered to Lender and except for such changes as are
specifically permitted under the Credit Agreement. In addition, other than as
waived in Section 2 hereof, Borrower and each Guarantor has complied
with and is in compliance with all of the covenants set forth in the Credit
Agreement, as amended hereby, including, but not limited to, those set forth in
Section VII thereof.

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6.6   
No Event of Default. As of the date hereof, no Event of Default under
Section VII of the Credit Agreement, as amended hereby, or event or condition
which, with the giving of notice or the passage of time, or both, would
constitute an Event of Default, has occurred or is continuing.

6.7    
No Subordinated Debt Default. As of the date hereof, no default under
any of the documents evidencing or securing any of the Subordinated Debt, or
event or condition which, with the giving of notice or the passage of time, or
both, would constitute a default under any of the documents evidencing or
securing any of the Subordinated Debt, has occurred or is continuing.

6.8    
Schedules to Credit Agreement. Other than as shown by the updated
Schedules attached hereto as Exhibit B, the Schedules attached to the
Credit Agreement are true and correct as of the date hereof.

7.      
CONDITIONS PRECEDENT. This Sixth Amendment shall become effective as of
the date above first written after receipt by Lender of the following:

7.1    
Sixth Amendment. This Sixth Amendment executed by Borrower, the
Guarantors, and Lender.

7.2    
Resolutions. A certified copy of Resolutions of the board of directors
of Borrower and each Guarantor authorizing the execution, delivery and
performance of this Sixth Amendment and related loan documents.

7.3    
Certificate of Good Standing. Certificates of Good Standing for Borrower
and each Guarantor from their respective jurisdictions of organization.

7.4    
Other Documents. Such other documents, certificates and/or opinions of
counsel as Lender may request.

8.      
GENERAL.

8.1    
Governing Law; Severability. This Sixth Amendment shall be construed in
accordance with and governed by the laws of Illinois. Wherever possible each
provision of the Credit Agreement and this Sixth Amendment shall be interpreted
in such manner as to be effective and valid under applicable law, but if any
provision of the Credit Agreement and this Sixth Amendment shall be prohibited by
or invalid under such law, such provision shall be ineffective to the extent of
such prohibition or invalidity, without invalidating the remainder of such
provision or the remaining provisions of the Credit Agreement and this Sixth
Amendment.

8.2    
Successors and Assigns. This Sixth Amendment shall be binding upon
Borrower, the Guarantors, and Lender and their respective successors and
assigns, and shall inure to the benefit of Borrower, the
Guarantors, and Lender and the successors and assigns of Lender.

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8.3    
Waiver of Claims. Borrower hereby acknowledges, agrees and affirms that
it possesses no claims, defenses, offsets, recoupment or counterclaims of any
kind or nature against or with respect to the enforcement of the Credit Agreement,
as amended hereby, the Revolving Note or any other Loan Document (collectively
referred to herein as the Claims), nor does Borrower now have knowledge of
any facts that would or might give rise to any Claims. If facts now exist which
would or could give rise to any Claim against or with respect to the
enforcement of the Credit Agreement as amended hereby, the Revolving Note,
and/or any other Loan Documents, Borrower hereby unconditionally, irrevocably
and unequivocally waives and fully releases any and all such Claims as if such
Claims were the subject of a lawsuit, adjudicated to final judgment from which
no appeal could be taken and therein dismissed with prejudice.

8.4    
Continuing Force and Effect of Loan Documents and Guaranty. Except as
specifically modified or amended by the terms of this Sixth Amendment, all
other terms and provisions of the Credit Agreement and the other Loan Documents
are incorporated by reference herein, and in all respects, shall continue in
full force and effect. Borrower, by execution of this Sixth Amendment, hereby
reaffirms, assumes and binds itself to all of the obligations, duties, rights,
covenants, terms and conditions that are contained in the Credit Agreement and
the other Loan Documents. Each of the Guarantors, by execution of this Sixth
Amendment, hereby reaffirms, assumes and binds itself to all of the
obligations, duties, rights, covenants, terms and conditions that are contained
in Guaranty.

8.5    
Financing Statements. Borrower hereby irrevocably authorizes Lender at
any time and from time to time to file in any jurisdiction any initial UCC
financing statements and/or amendments thereto that (a) describe the
Collateral, and (b) contain any other information required by part 5 of
Article 9 of the UCC for the sufficiency or filing office acceptance of any
financing statement or amendment.

8.6    
References to Credit Agreement. Each reference in the Credit Agreement
to this Agreement, hereunder, hereof, or words of like import, and each
reference to the Credit Agreement in any and all instruments or documents
delivered in connection therewith, shall be deemed to refer to the Credit
Agreement, as amended hereby.

8.7    
Expenses. Borrower shall pay all costs and expenses in connection with
the preparation of this Sixth Amendment and other related loan documents,
including, without limitation, reasonable attorneys fees and time charges of
attorneys who may be employees of Lender or any affiliate or parent of Lender.
Borrower shall pay any and all stamp and other taxes, UCC search fees, filing
fees and other costs and expenses in connection with the execution and delivery
of this Sixth Amendment and the other instruments and documents to be delivered
hereunder, and agrees to save Lender harmless from and against any and all
liabilities with respect to or resulting from any delay in paying or omission
to pay such costs and expenses.

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8.8    
Counterparts. This Sixth Amendment may be executed in any number of
counterparts, all of which shall constitute one and the same agreement.

[Signatures on following page]

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IN
WITNESS WHEREOF, the parties hereto have executed this Sixth Amendment to the
Amended and Restated Credit Agreement and Reaffirmation of Guaranties as of the
date first above written.

| |                                                            |                                                                  
| | ---------------------------------------------------------- | -----------------------------------------------------------------
| | Borrower:                                                 
| |                                                           
| | QUIXOTE
  CORPORATION,                                    
| | a Delaware
  corporation, as Borrower                     
| |                                                           
| | By:                                                        | /s/ Daniel
P. Gorey                                              
| |                                                            |                                                                  
| | Name:                                                      | Daniel P.
  Gorey                                                
| | Title:                                                     | Executive
  Vice President, Chief Financial Officer and Treasurer
| |                                                            |                                                                  
| | Guarantors:                                               
| |                                                           
| | QUIXOTE
  TRANSPORTATION SAFETY, INC. TRANSAFE CORPORATION
| | ENERGY
  ABSORPTION SYSTEMS, INC.                         
| | ENERGY
  ABSORPTION SYSTEMS (AL) LLC SURFACE SYSTEMS, INC.
| | NU-METRICS,
  INC.                                        
| | HIGHWAY
  INFORMATION SYSTEMS, INC.                       
| |                                                           
| | By:                                                        | /s/ Daniel
  P. Gorey                                            
| |                                                            |                                                                  
| | Name:                                                      | Daniel P.
  Gorey                                                
| | Title:                                                     | Executive
  Vice President, Chief Financial Officer and Treasurer
| |                                                            |                                                                  
| | Lender:                                                   
| |                                                            |                                                                  
| | BANK OF
  AMERICA, N.A., a national banking association   
| |                                                            |                                                                  
| | By:                                                        | /s/ Chris D.
  Buckner                                           
| |                                                            |                                                                  
| | Name:                                                      | Chris D.
  Buckner                                               
| | Title:                                                     | Senior Vice
  President                                          

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Schedule I

Organizational
Identification Numbers

|                                      |  |              |  |         
|------------------------------------- |  | ------------ |  | --------
|CORPORATION                           |  | STATE        |  | STATE ID
|                                      |  |              |  |         
|                                      |  |              |  |         
|Quixote
  Corporation                 |  | Delaware     |  | 0720523 
|Quixote
  Transportation Safety, Inc. |  | Delaware     |  | 2803660 
|Transafe
  Corporation                |  | Delaware     |  | 3197646 
|Energy
  Absorption Systems, Inc.     |  | Delaware     |  | 0904033 
|Energy
  Absorption (AL) LLC          |  | Delaware     |  | 3539333 
|Surface
  Systems, Inc.               |  | Missouri     |  | 00157025
|Nu-Metrics,
  Inc.                    |  | Pennsylvania |  | 978728  
|Highway
  Information Systems, Inc.   |  | Delaware     |  | 2867376 

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Exhibit A

Exhibit Q 
Borrowing Base Certificate

This
Borrowing Bank Certificate (this Certificate) is given by Quixote
Corporation, a Delaware corporation (Borrower), pursuant to, and in
accordance with, the terms and provisions of Section 7.1(A)(v) of that
certain Amended and Restated Credit Agreement dated as of April 20, 2005 (as
the same may be amended, restated, supplemented or otherwise modified from time
to time, the Credit Agreement) by and between Borrower and Bank of America,
N.A. (Lender). Capitalized terms used herein without definition shall have
the meanings set forth in the Credit Agreement.

The
officer executing this Certificate is an Authorized Officer of Borrower and as
such is duly authorized to execute and deliver this Certificate on behalf of
Borrower. By executing this Certificate such officer hereby certifies to Lender
that attached as Schedule I is a correct calculation of the Borrowing Base
Amount.

| |                                                    | 
| | -------------------------------------------------- | 
| | QUIXOTE
  CORPORATION                             
| |                                                   
| | By:
  __________________________________________  
| | Name:
  ________________________________________  
| | Title:
  _________________________________________

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