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                                                                   EXHIBIT 10.56

                                   EXHIBIT C

                             AMENDMENT NO. 3 TO THE
                          ABM INDUSTRIES INCORPORATED
                           "PRICE-VESTED" PERFORMANCE
                               STOCK OPTION PLAN

     ABM INDUSTRIES INCORPORATED, having established the ABM Industries
Incorporated "Price-Vested" Performance Stock Option Plan (the "Plan")
effective as of December 17, 1996, hereby amends the Plan, effective as of
September 22, 1999 as follows:

     1.   Section 6.b. of the Plan is amended to insert the following after the
sentence that reads, "For purposes of the Plan, a "Change of Control" shall mean
the happening of any of the following events:"

          (i)   the acquisition (other than by ABM or by an employee benefit
     plan or related trust sponsored or maintained by ABM), directly or
     indirectly, in one or more transactions, by any person or by any group of
     persons, within the meaning of Section 13(d) or 14(d) of the Securities
     Exchange Act of 1934 or any comparable successor provisions (the "Exchange
     Act"), of beneficial ownership (within the meaning of Rule 13d-3 of the
     Exchange Act) of twenty-five percent or more of either the outstanding
     shares of common stock or the combined voting power of ABM's outstanding
     voting securities entitled to vote generally, if the acquisition was not
     previously approved by the existing directors;

          (ii)  the acquisition (other than by ABM or by an employee benefit
     plan or related trust sponsored or maintained by ABM), directly or
     indirectly, in one or more transactions, by any such person or by any group
     of persons of beneficial ownership (within the meaning of Rule 13d-3 of the
     Exchange Act) of fifty percent or more of either the outstanding shares of
     common stock or the combined voting power of ABM's outstanding voting
     securities entitled to vote generally, whether or not the acquisition was
     approved by the existing directors, other than an acquisition that complies
     with clause (x) and (y) of paragraph (iii);

          (iii) consummation of a reorganization, merger or consolidation of ABM
     or the sale or other disposition of all or substantially all of ABM's
     assets unless immediately following such event, (x) all or substantially
     all of the stockholders of ABM immediately prior to such event own,
     directly or indirectly, seventy-five percent or more of the then
     outstanding voting securities entitled to vote generally of the resulting
     corporation (including without limitation, a corporation which as a result
     of such event owns ABM or all or substantially all of ABM's assets either
     directly or through one or more subsidiaries) in substantially the same
     proportions as their ownership of ABM's outstanding voting securities
     entitled to vote generally immediately prior to such event and (y) the
     securities of the surviving or
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          resulting corporation received or retained by the stockholders of ABM
          is publicly traded;

               (iv) approval by the stockholders of the complete liquidation or
          dissolution of ABM; or

               (v)  a greater than one-third change in the composition of the
          Board of Directors within 24 months if not approved by a majority of
          the pre-existing directors.

     provided that, in respect of options outstanding as of September 22, 1999,
     a "Change of Control" shall also mean the happening at any of the following
     events:

          IN WITNESS WHEREOF, ABM INDUSTRIES INCORPORATED, by its duly
authorized officer, has executed this Amendment No. 2 on the date indicated
below.

                                        ABM INDUSTRIES INCORPORATED



Dated: 9/22/99                          By: /s/ LORRAINE P. O'HARA
                                           -----------------------------

                                        Title:  Assistant Secretary



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