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                                                                   EXHIBIT 10.64



                      INVESTOR RELATIONS SERVICES AGREEMENT

         This INVESTOR RELATIONS SERVICES AGREEMENT (this "Agreement"), made and
entered into this 31st day of March, 2000, by and between HighwayMaster
Communications, Inc., a Delaware Corporation, having a principal place of
business at 1155 Kas Drive, Suite 100, Richardson, Texas, 75081
("HighwayMaster"), and N.D. Hamilton Associates, Inc., a Florida Corporation,
having a principal place of business at 115 S.E. Spanish Trail, Boca Raton,
Florida 33432 ("Hamilton").

                                    ARTICLE 1

                           INVESTOR RELATIONS SERVICES

1.1      Investor Relations Services Provided. Hamilton agrees to provide
         investor relations consultation services to HighwayMaster during the
         Contract Term (as defined in Section 2.1 below). These professional
         services will be directed toward assisting HighwayMaster in the
         accomplishment of certain corporate investor relations objectives
         including, but not limited to, the following:

         1.0.1    Increasing the investment community's awareness of
                  HighwayMaster by conducting an active investor relations
                  program designed to gain recognition from the investment
                  community of HighwayMaster's long-term investment potential.

         1.1.1    Assisting HighwayMaster in obtaining at least one (1)
                  national, sell side analyst from a quality, recognized
                  brokerage to follow HighwayMaster and provide quarterly
                  updates to the public.

         1.1.2    Assisting HighwayMaster in obtaining at least one (1)
                  regional, sell side analyst of high recognition and quality,
                  to follow HighwayMaster and provide quarterly updates to the
                  public.

         1.1.3    Assisting HighwayMaster in obtaining two (2) nationally
                  recognized analysts to each prepare a research report on
                  HighwayMaster.

         1.1.4    Assisting HighwayMaster with the distribution of investor
                  packages to investors and analysts during the Contract Term.

                                    ARTICLE 2

                                  CONTRACT TERM

1.2      Term. Hamilton shall provide the services described in Article 1 above
         for a period commencing on the date of execution of this Agreement and
         terminating six (6) months thereafter (the "Contract Term").


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                                    ARTICLE 3

                             SERVICE FEES & BILLING

1.3      Fees & Billing. HighwayMaster shall provide the following compensation
         to Hamilton for the services rendered under this Agreement:

         3.0.1    FIXED MONTHLY FEE. HighwayMaster shall compensate Hamilton at
                  the rate of $3,500.00 per month for each month during the
                  Contract Term payable on the first day of each month.

         1.3.1    Stock Options. HighwayMaster shall grant to Hamilton the
                  following option to purchase shares of common stock of
                  HighwayMaster at an exercise price of $5.63 per share upon the
                  occurrence of the following events:

                  1.3.1.1  5,000 stock options upon the execution of this
                           Agreement.

                  1.3.1.2  3,000 stock options if, as a result of Hamilton's
                           efforts, one (1) national, sell side analyst from a
                           quality, recognized brokerage firm begins to follow
                           HighwayMaster and provides ongoing quarterly updates
                           to the public regarding HighwayMaster; provided,
                           however, that such coverage must commence during the
                           Contract Term.

                  1.3.1.3  3,000 stock options if, as a result of Hamilton's
                           efforts, one (1) regional, sell side analyst of high
                           recognition and quality, begins to follow
                           HighwayMaster and provides quarterly updates to the
                           public regarding HighwayMaster; provided, however,
                           that such coverage must commence during the Contract
                           Term.

                  1.3.1.4  3,000 stock options if, as a result of Hamilton's
                           efforts, two (2) nationally recognized analysts each
                           prepare a research report on HighwayMaster prior to
                           the end of the Contract Term.

                  1.3.1.5  3,000 stock options on the six month anniversary of
                           this Agreement, if during the Contract Term, Hamilton
                           has used his best efforts to distribute investor
                           packages to investors and analysts.

         1.3.2    Vesting and Exercise of Vested Options. Any stock options
                  earned by Hamilton during the Contract Term shall vest on the
                  one (1) year anniversary of the execution of this Agreement.
                  In order to exercise any vested options, Hamilton must deliver
                  written notice to HighwayMaster indicating the number of
                  vested options which Hamilton desires to exercise and a
                  cashier's check in the amount of the exercise price.



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         1.3.3    Taxes. HighwayMaster shall issue to Hamilton a Form 1099-Misc.
                  following the end of each calendar year in which Hamilton
                  exercises any portion of the options. Hamilton shall be
                  responsible for the payment of all taxes incurred as a result
                  of the exercise of the stock options and the sale of common
                  stock issued as a result thereof.

                  1.3.4       Registration of Stock Issued Upon Exercise of
                              Stock Options.

                  1.3.4.1     HighwayMaster shall file a registration statement
                              on the appropriate form under the Securities Act,
                              within ninety (90) days from the date of vesting
                              of Hamilton's options covering the registration of
                              the resale of the shares of common stock for which
                              options are earned by Hamilton under Section 3.1.2
                              (the "Registrable Shares"). In connection with
                              such registration statement, HighwayMaster shall:

                  1.3.4.1.1   Use its reasonable best efforts to cause such
                              registration statement to become effective and
                              keep such registration statement effective until
                              the earlier of (x) one hundred twenty (120) days
                              from the date of effectiveness or (y) Hamilton's
                              disposition of all of the Registrable Shares;

                  1.3.4.1.2   Use its reasonable best efforts to prepare and
                              file with the Securities and Exchange Commission
                              (the "SEC") such amendments and supplements to
                              such registration statement as may be necessary to
                              comply with the applicable provisions of the
                              Securities Act of 1933, as amended (the
                              "Securities Act");

                  1.3.4.1.3   Use its reasonable best efforts to register and
                              qualify the Registrable Shares covered by such
                              registration statement under such other securities
                              or Blue Sky laws of such jurisdictions as shall be
                              reasonably requested by Hamilton, and to keep such
                              registration or qualification effective during the
                              period such registration statement is to be kept
                              effective, provided, however, that HighwayMaster
                              shall not be required to become subject to
                              taxation, qualify to do business or file a general
                              consent to service of process in any such
                              jurisdictions;

                  1.3.4.1.4   Use its reasonable best efforts to maintain the
                              authorization for quotation of the securities
                              covered by such registration statement on the
                              NASDAQ SmallCap Market; and

                  1.3.4.1.5   Notify Hamilton, at any time when Hamilton must
                              suspend offers or sales of the Registrable Shares
                              under the registration statement, either because
                              the prospectus included in such registration
                              statement is required to be amended for any
                              reason, such as an


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                           amendment under the Securities Act to provide current
                           information, or because the prospectus includes an
                           untrue statement of a material fact or omits to state
                           a material fact required to be stated therein or
                           necessary to make the statements therein not
                           misleading in the light of the circumstances then
                           existing. HighwayMaster shall use its reasonable best
                           efforts to enable Hamilton to promptly recommence
                           offers and sales under the registration statement.
                           Notwithstanding the foregoing and anything to the
                           contrary set forth in this Section 3.1.5, Hamilton
                           acknowledges that there may occasionally be times
                           when HighwayMaster must suspend the use of the
                           prospectus included in such registration statement
                           until such time as an amendment to the registration
                           statement has been filed by HighwayMaster and
                           declared effective by the SEC, or until such time as
                           HighwayMaster has filed an appropriate report with
                           the SEC pursuant to the Securities Exchange Act of
                           1934, as amended (the "1934 Act"). Hamilton hereby
                           covenants that he will not offer or sell any shares
                           of the Registrable Shares pursuant to such prospectus
                           during the period commencing when HighwayMaster
                           notifies Hamilton of the suspension of the use of
                           such prospectus and the reason therefor, and ending
                           when HighwayMaster notifies Hamilton in writing that
                           it may thereafter effect offers and sales pursuant to
                           such prospectus.

                  3.0.1.1  It is a condition precedent to the obligations of
                           HighwayMaster to take any action pursuant to this
                           Section 3.1.5 hereof with respect to the Registrable
                           Shares, that Hamilton shall furnish to HighwayMaster
                           such information regarding itself, the Registrable
                           Shares held thereby and the intended method of
                           disposition of such securities as shall be required
                           to effect the registration of such Registrable Shares
                           and as may be required from time to time to keep such
                           registration current.

                  1.3.4.2  Except as otherwise provided herein, all expenses
                           incurred by or on behalf of HighwayMaster in
                           connection with registrations, filings or
                           qualifications pursuant to this Section 3.1.5,
                           including without limitation all registration, filing
                           and qualification fees, the fees and expenses
                           incurred in connection with the listing of the
                           Registrable Shares to be registered on each security
                           exchange on which shares of HighwayMaster's common
                           stock are then listed, printer's and accounting fees,
                           and fees and disbursements of counsel for
                           HighwayMaster, shall be borne by HighwayMaster. In no
                           event shall HighwayMaster be obligated to bear
                           underwriting, brokerage or related fees, discounts or
                           commissions or the fees or expenses of counsel or
                           advisors to Hamilton.



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                  1.3.4.3  Each of HighwayMaster and Hamilton shall agree to
                           such other reasonable and customary arrangements,
                           undertakings and indemnifications with respect to the
                           registration of the Registrable Shares to be received
                           by Hamilton pursuant to the Agreement as may be
                           requested by any of them, but shall not be obligated
                           to enter into any underwriting arrangements.

                  1.3.4.4  HighwayMaster covenants that it will at all times use
                           its reasonable best efforts to timely file any
                           reports required to be filed by it under the
                           Securities Act and the 1934 Act and that it will take
                           such other actions as may be reasonably necessary to
                           enable Hamilton to sell the shares of common stock
                           without registration under applicable exemptions
                           provided for under the Securities Act including,
                           without limitation, Rule 144.

                  1.3.4.5  Unless and until the registration statement is
                           effective, any stock certificates issued to Hamilton
                           as a result of the exercise of the stock options
                           shall bear the following restrictive legend:

                           "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE
                           NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
                           AS AMENDED, OR SECURITIES LAWS OF ANY STATE, AND
                           NEITHER THE SECURITIES NOR ANY INTEREST THEREIN MAY
                           BE SOLD OR OTHERWISE TRANSFERRED IN THE ABSENCE OF
                           SUCH REGISTRATION OR AN APPLICABLE EXEMPTION
                           THEREUNDER."

1.4      Expenses. Hamilton shall be responsible for paying any and all expenses
         incurred by Hamilton in performing the services hereunder.
         HighwayMaster shall have no liability for any expenses incurred by
         Hamilton in performing the services hereunder.





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                                    ARTICLE 4

                                  MISCELLANEOUS



1.5      Indemnification to Hamilton. HighwayMaster shall indemnify and hold
         harmless Hamilton, its officers, agents, and representatives (each an
         "Indemnified Hamilton Party") from and against any and all losses,
         claims, damages or liabilities which either such Indemnified Hamilton
         Party may incur, including any amount paid in settlement of any claim,
         action or proceeding commenced or threatened, and any and all expenses
         reasonably incurred (including reasonable and necessary attorney's
         fees) in connection with any such claim, action or proceeding insofar
         as such loss, claim, damages, liabilities, actions, proceedings or
         expenses (collectively "Hamilton Losses") resulted from false and/or
         incorrect information, false representations, false and/or incorrect
         reports or other false and/or incorrect data furnished by HighwayMaster
         or its authorized representatives to Hamilton in writing for use in
         connection with the services to be provided by Hamilton pursuant to the
         terms of this Agreement, except that no Indemnified Hamilton Party
         shall be so indemnified to the extent that any Hamilton Losses arise
         out of such Indemnified Hamilton Party's negligence or willful
         misconduct or bad faith in connection with the performance of such
         Indemnified Hamilton Party's services hereunder and except that
         HighwayMaster shall not be liable in any event for any amount paid in
         settlement of any claim or any litigation, threatened or commenced,
         whatsoever if such settlement is effected without the written consent
         of HighwayMaster (which consent shall not be reasonably withheld).
         Hamilton shall give prompt written notice to HighwayMaster of any claim
         or action commenced or threatened against each Indemnified Hamilton
         Party in respect of which indemnity may be sought thereunder. If it so
         elects within a reasonable time after receipt of such notice,
         HighwayMaster may assume the defense of such claim or action. If
         HighwayMaster assumes the defense of such claim or action,
         HighwayMaster will not be liable for any fees and expenses of counsel
         for an Indemnified Hamilton Party incurred thereafter in connection
         with such claim or action. Any separate counsel representing an
         Indemnified Hamilton Party shall cooperate with HighwayMaster and its
         counsel in the defense of such claim or action. The failure of Hamilton
         to promptly notify HighwayMaster of its receipt of commencement of any
         claims or action in respect of which indemnity may be sought will
         relieve HighwayMaster from any liability HighwayMaster may have to the
         extent that such delay in notification prejudices HighwayMaster's
         defense of such claim or action.

1.6      Indemnification to HighwayMaster. Hamilton shall indemnify and hold
         harmless HighwayMaster, its parents, subsidiaries, affiliates,
         officers, agents, and representatives (each an "Indemnified
         HighwayMaster Party") from and against any and all losses, claims,
         damages or liabilities which either such Indemnified HighwayMaster
         Party may incur, including any amount paid in settlement of any claim,
         action or proceeding commenced or threatened, and any and all expenses
         reasonably incurred (including reasonable and necessary attorney's
         fees) in connection with any such claim, action or proceeding insofar
         as such loss, claim, damages, liabilities, actions, proceedings or
         expenses (collectively "HighwayMaster Losses") resulted from the acts
         and/or omissions of Hamilton or its authorized representatives in
         performing the services to be provided by Hamilton pursuant to the
         terms of this Agreement, except that no Indemnified HighwayMaster Party
         shall be so indemnified to the extent that any HighwayMaster Losses
         arise out of such Indemnified HighwayMaster Party's negligence, willful
         misconduct, or provision of false or incorrect information to



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         Hamilton and except that Hamilton shall not be liable in any event for
         any amount paid in settlement of any claim or any litigation,
         threatened or commenced, whatsoever if such settlement is effected
         without the written consent of the Hamilton (which consent shall not be
         reasonably withheld). HighwayMaster shall give prompt written notice to
         Hamilton of any claim or action commenced or threatened against each
         Indemnified HighwayMaster Party in respect of which indemnity may be
         sought thereunder. If it so elects within a reasonable time after
         receipt of such notice, Hamilton may assume the defense of such claim
         or action. If Hamilton assumes the defense of such claim or action,
         Hamilton will not be liable for any fees and expenses of counsel for an
         Indemnified HighwayMaster Party incurred thereafter in connection with
         such claim or action. Any separate counsel representing an Indemnified
         HighwayMaster Party shall cooperate with Hamilton and its counsel in
         the defense of such claim or action. The failure of HighwayMaster to
         promptly notify Hamilton of its receipt of commencement of any claims
         or action in respect of which indemnity may be sought will relieve
         Hamilton from any liability Hamilton may have to the extent that such
         delay in notification prejudices Hamilton's defense of such claim or
         action.

1.7      Confidentiality. "HighwayMaster Confidential Information" shall mean,
         for purposes of this Section 4.3, the technical and business
         information which is proprietary and confidential to HighwayMaster, and
         such other information marked "Confidential" and disclosed to Hamilton
         by HighwayMaster pursuant to this Agreement. Hamilton shall hold all
         HighwayMaster Confidential Information in confidence and shall not
         disclose the same to third parties without the prior written permission
         of HighwayMaster, and shall not use HighwayMaster Confidential
         Information other than for the benefit of HighwayMaster during the
         Contract Term and for such period following the termination of this
         Agreement as HighwayMaster Confidential Information remains a trade
         secret of HighwayMaster.

1.8      Relationship of the Parties. It is the intention of the parties that
         Hamilton be an independent contractor and not an employee, agent, joint
         venturer, or partner of HighwayMaster. Nothing in this Agreement shall
         be interpreted or construed as creating or establishing the
         relationship of employer and employee between HighwayMaster and either
         Hamilton or any employee or agent of Hamilton. Nothing in this
         Agreement shall be construed to give either party the power to direct
         or control the daily activities of the other party, or to constitute
         the parties as principal and agent, employer and employee, franchisor
         and franchisee, partners, joint venturers, co-owners, or otherwise as
         participants in a joint undertaking. HighwayMaster and Hamilton
         understand and agree that, except as specifically provided in this
         Agreement, HighwayMaster does not grant Hamilton the power or authority
         to make or give any agreement, statement, representation, warranty, or
         other commitment on behalf of HighwayMaster, or to enter into any
         contract or otherwise incur any liability or obligation, express or
         implied, on behalf of HighwayMaster, or to transfer, release, or waive
         any right, title, or interest of HighwayMaster.

1.9      No False Representations. Hamilton shall (1) conduct business in a
         manner that reflects favorably at all times on HighwayMaster's products
         and services and the reputation of HighwayMaster; (2) avoid deceptive,
         misleading, or unethical practices that are or might be



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         detrimental to HighwayMaster, its products and services including any
         disparagement of HighwayMaster, its products and services; (3) make no
         false or misleading representations with regard to HighwayMaster, its
         products and services; and (4) refrain from publishing or employing any
         misleading or deceptive advertising material regarding HighwayMaster,
         its products and services.

1.10     Nonexclusive. Hamilton shall retain the right to perform services for
         others during the terms of this Agreement; provided, that
         HighwayMaster's ownership and confidentiality of work product is not
         jeopardized in any way. HighwayMaster shall retain the right to cause
         similar services to be performed by its own personnel and/or other
         contractors during the Contract Term.

1.11     Compliance With Law. Hamilton shall comply with all applicable federal,
         state, and local laws and regulations in performing its duties
         hereunder including, but not limited to, the Securities Act (and any
         rules and regulations promulgated thereunder), the 1934 Act (and any
         rules and regulations promulgated thereunder), and the NASDAQ Stock
         Exchange Rules and Regulations.

1.12     Method of Performing Services. Hamilton, in conjunction with its
         personnel, will determine the method, details, and means of performing
         the services to be performed for HighwayMaster pursuant to the terms of
         this Agreement. HighwayMaster shall have no right to, and shall not,
         control the manner or determine the method which Hamilton performs
         services pursuant to this Agreement; provided, however, that
         HighwayMaster may require Hamilton's personnel to observe at all times
         the security and safety policies of HighwayMaster. Notwithstanding the
         preceding, HighwayMaster shall be entitled to exercise a broad general
         power of supervision and control over the results of work performed by
         Hamilton to ensure satisfactory performance.

1.13     Scheduling. In performing services under this Agreement, Hamilton
         shall, to the extent reasonably possible, accommodate work schedule
         requests of HighwayMaster. Should any personnel of Hamilton be unable
         to perform scheduled services because of illness, resignation, or other
         causes beyond Hamilton's reasonable control, Hamilton will replace such
         personnel within a reasonable time.

1.14     Record Keeping. Hamilton shall maintain complete and accurate
         accounting records, in a form in accordance with standard accounting
         practices, to substantiate Hamilton's charges hereunder. Such records
         shall include payroll records and time sheets, and Hamilton shall
         retain such records for a period of one (1) year from the date of final
         payment hereunder.

1.15     Hamilton's Agreements With Personnel. Hamilton shall obtain and
         maintain in effect written agreements with each of its employees and/or
         independent contractors who participate in providing services to
         HighwayMaster under this Agreement. Such agreements shall contain terms
         sufficient to enable Hamilton to comply with all provisions of this
         Agreement, shall establish a duty of confidentiality enforceable by
         HighwayMaster and shall confirm that such



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         personnel shall have no status as employees of HighwayMaster and no
         claim under any HighwayMaster employee benefit plan.

1.16     No Discrimination. Hamilton agrees that in the performance of this
         Agreement it will not discriminate or permit discrimination against any
         person or group of persons on the grounds of sex, race, color,
         religion, or natural origin in any manner prohibited by the laws of the
         United States.

1.17     Force Majeure. Neither party hereto shall be responsible for any
         failure to perform due to unforeseen circumstances or to causes beyond
         its reasonable control, including but not limited to acts of God, war,
         riot, embargoes, acts of civil or military authorities, fire, floods,
         accidents, strikes, or shortages of transportation, facilities, fuel,
         energy, labor, or materials. In the event of any such delay, said party
         is excused from performance for a period equal to the time of such
         delay. In the event such delay exceeds sixty (60) days, either party
         may terminate this Agreement.

1.18     Insurance. Hamilton shall secure and maintain adequate workmen's
         compensation, disability benefits, unemployment insurance and the like,
         if required by the law of each state wherein Hamilton shall perform
         services for HighwayMaster. Hamilton further agrees to maintain
         comprehensive general and vehicular liability insurance for claims for
         damages arising out of bodily injury (including death) and property
         damage, caused by, or arising out of, acts or omissions of its
         employees. The minimum limits of such insurance shall be $300,000.00
         for each person and $300,000.00 for each incident because of bodily
         injury and $300,000.00 because of property damage for each incident.
         Certificates of insurance shall be furnished to HighwayMaster at the
         commencement of this Agreement and at the renewal date or dates of all
         such insurance policies for as long as this Agreement remains in
         effect. In no event shall any such insurance be canceled without thirty
         (30) days prior written notice to HighwayMaster by Hamilton.

1.19     Entire Agreement of the Parties. This Agreement supersedes any and all
         agreements, either oral or written, between the parties hereto with
         respect to the rendering of services by Hamilton for HighwayMaster and
         contains all the covenants and agreements between the parties with
         respect to the rendering of such services in any manner whatsoever.
         Each party to this Agreement acknowledges that no representations,
         inducements, promises, or agreements, orally or otherwise, have been
         made by any party, or anyone acting on behalf of any party, that are
         not embodied herein, and that no other agreement, statement, or promise
         not contained in this agreement shall be valid or binding. Any
         modification of this Agreement will be effective only if it is in
         writing signed by the party to be charged.

1.20     Partial Invalidity. If any provision in this agreement is held by a
         court of competent jurisdiction to be invalid, void, or unenforceable,
         the remaining provisions will nevertheless continue in full force
         without being impaired or invalidated in any way.



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1.21     Termination. Either party may terminate the Agreement upon thirty (30)
         days written notice to the other party to the Agreement. In the event
         that HighwayMaster terminates this Agreement, other than for cause,
         HighwayMaster shall pay for services rendered by Hamilton prior to the
         effective date of the termination.

1.22     Termination for Cause. If a party materially defaults in its
         performance under this Agreement, other than non-payment of amounts due
         to Hamilton, and fails to either substantially cure such default within
         thirty (30) days after receiving written notice specifying the default
         or, for those defaults which cannot reasonably be cured within thirty
         (30) days, promptly commence curing such default and thereafter proceed
         with all due diligence to substantially cure the same, then the party
         not in default may terminate this Agreement as of a date specified in
         such notice; provided, that any such termination by a party for cause
         shall not serve as a waiver of any rights or remedies such party may
         have against the breaching party at law or in equity. Notwithstanding
         the preceding, in the event that HighwayMaster terminates this
         Agreement for cause pursuant to this Section 4.18, any and all options
         issued to Hamilton under Section 3.1.2 shall be forfeited as of the
         date of such termination.

1.23     Notices. Unless otherwise specifically provided, all notices required
         or permitted by this Agreement shall be in writing and may be delivered
         personally, or may be sent by facsimile or certified mail, return
         receipt requested, to the following addresses, unless the parties are
         subsequently notified of any change of address in accordance with this
         Section 4.19:

                  If to HighwayMaster:

                  HighwayMaster Communications, Inc.
                  1155 Kas Drive, Suite 100
                  Richardson, Texas 75081
                  Attention: General Counsel
                  Facsimile: (972) 301-2263

                  If to Hamilton:

                  N.D. Hamilton Associates, Inc
                  Attn: David Hamilton
                  115 S.E. Spanish Trail
                  Boca Raton, Florida 33432
                  Attention: David Hamilton
                  Facsimile: (561) 393-0068____

         Any notice shall be deemed to have been received as follows: (1) by
         personal delivery, upon receipt; (2) by facsimile upon receipt; (3) by
         certified mail, five (5) business days after delivery to the U.S.
         postal authorities by the party serving notice. If notice is sent by
         facsimile, a confirming copy of the same shall be sent by mail to the
         same address.



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1.24     GOVERNING LAW; CONSENT TO JURISDICTION AND VENUE. THIS AGREEMENT SHALL
         BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE
         OF TEXAS, WITHOUT GIVING EFFECT TO THE CONFLICT OF LAWS (RULES) OR
         CHOICE OF LAWS (RULES) THEREOF. HAMILTON HEREBY CONSENTS TO THE
         EXCLUSIVE PERSONAL JURISDICTION AND VENUE OF THE STATE DISTRICT COURT
         RESIDING IN DALLAS COUNTY, DALLAS, TEXAS (OR IF APPLICABLE, THE FEDERAL
         DISTRICT COURT FOR THE NORTHERN DISTRICT OF TEXAS, DALLAS DIVISION) FOR
         ALL LITIGATION WHICH MAY BE BROUGHT WITH RESPECT TO OR ARISING OUT OF
         THE TERMS OF AND THE TRANSACTIONS AND RELATIONSHIPS CONTEMPLATED BY
         THIS AGREEMENT.

1.25     Assignment. Hamilton is being retained as per this Agreement because of
         HighwayMaster's confidence in Hamilton's abilities which confidence is
         personal in nature. This Agreement shall not be assignable by either
         party without the prior written consent of the other party which shall
         not be unreasonably withheld, and Hamilton may not delegate its duties
         hereunder without the prior written consent of HighwayMaster. Any
         attempt by Hamilton to assign any of its rights or delegate any of its
         duties hereunder without the prior written consent of HighwayMaster
         shall be null and void.

1.26     Successors. This Agreement shall inure to the benefit of, and be
         binding upon, Hamilton and HighwayMaster, their successors and assigns.

1.27     Survival. In the event of any termination of this Agreement, Sections
         3.1, 4.1, 4.2, 4.3, 4.4, 4.5 and 4.20 hereof shall survive and continue
         in effect.

         IN WITNESS THEREOF, HighwayMaster and Hamilton have caused this
Investor Relations Service Agreement to be signed and delivered by their duly
authorized officers, all as of the date first hereinabove written.









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HIGHWAYMASTER
COMMUNICATIONS, INC.,                       N.D. HAMILTON ASSOCIATES, INC.
A DELAWARE CORPORATION

By: /s/ W. MICHAEL SMITH                    By: /s/ DAVID HAMILTON
    -----------------------------               -----------------------------

Title: CFO                                  Title: PRESIDENT
       --------------------------                  --------------------------

Date: April 3, 2000                         Date: March 31, 2000
      ---------------------------                 ---------------------------











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