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                                                                    EXHIBIT 4(a)

                          AMENDMENT TO RIGHTS AGREEMENT

1.  GENERAL BACKGROUND. In accordance with Section 21 of the Rights Agreement
    between BankBoston, N.A., as Rights Agent (now known as "Fleet National
    Bank" (the "Rights Agent") and Quixote Corporation (the "Company") dated
    July 24, 1998, (the "Agreement"), the Rights Agent and the Company desire to
    amend the Agreement to appoint EquiServe Trust Company, N.A.

2.  EFFECTIVENESS. This Amendment shall be effective as of October 15, 2001 (the
    "Amendment") and all defined terms and definitions in the Agreement shall be
    the same in the Amendment except as specifically revised by the Amendment.

3.  REVISION. The section in the Agreement entitled "Change of Rights Agent" is
    hereby deleted in its entirety and replaced with the following:

    CHANGE OF RIGHTS AGENT. The Rights Agent or any successor Rights Agent may
    resign and be discharged from its duties under this Agreement upon 30 days'
    notice in writing mailed to the Company and to each transfer agent of the
    Common Stock or Preferred Stock, by registered or certified mail and to the
    holders of the Right Certificates by first-class mail. The Company may
    remove the Rights Agent or any successor Rights Agent upon 30 days' notice
    in writing mailed to the Rights Agent or successor Rights Agent, as the case
    may be, and to each transfer agent of the Common Stock or Preferred Stock,
    by registered or certified mail, and to the holders of the Right
    Certificates by first-class mail. If the Rights Agent shall resign or be
    removed or shall otherwise become incapable of acting, the Company shall
    appoint a successor to the Rights Agent. If the Company shall fail to make
    such appointment within a period of 30 days after giving notice of such
    removal or after it has been notified in writing of such resignation or
    incapacity by the resigning or incapacitated Rights Agent or by the holder
    of a Rights Certificate (who shall, with such notice, submit such holder's
    Rights Certificate for inspection by the Company), then any registered
    holder of any Rights Certificate may apply to any court of competent
    jurisdiction for the appointment of a new Rights Agent. Any successor Rights
    Agent, whether appointed by the Company or by such a court, shall be a
    corporation or trust company organized and doing business under the laws of
    the United States, in good standing, which is authorized under such laws to
    exercise corporate trust or stock transfer powers and is subject to
    supervision or examination by federal or state authority and which has
    individually or combined with an affiliate at the time of its appointment as
    Rights Agent a combined capital and surplus of at least $100 million
    dollars. After appointment, the successor Rights Agent shall be vested with
    the same powers, rights, duties and responsibilities as if it had been
    originally named as Rights Agent without



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    further act or deed; but the predecessor Rights Agent shall deliver and
    transfer to the successor Rights Agent any property at the time held by it
    hereunder, and execute and deliver any further assurance, conveyance, act or
    deed necessary for the purpose. Not later than the effective date of any
    such appointment the Company shall file notice thereof in writing with the
    predecessor Rights Agent and each transfer agent of the Common Stock or
    Preferred Stock, and mail a notice thereof in writing to the registered
    holders of the Right Certificates. Failure to give any notice provided for
    in this Section 21, however, or any defect therein, shall not affect the
    legality or validity of the resignation or removal of the Rights Agent or
    the appointment of the successor Rights Agent, as the case may be.

4.  Except as amended hereby, the Agreement and all schedules or exhibits
    thereto shall remain in full force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed
in their names and on their behalf by and through their duly authorized
officers, as of this 15th day of October, 2001.

QUIXOTE CORPORATION                            BANKBOSTON, N.A.

/s/ Joan R. Riley                              /s/ Katherine Anderson
-----------------                              ----------------------
By: Joan R. Riley                              By: Katherine Anderson
Title: Vice President & General Counsel        Title: Managing Director