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                                                                   EXHIBIT 10.63

                     LIMITED LIABILITY COMPANY AGREEMENT OF
                          HIGHWAYMASTER OF CANADA, LLC

                     (A DELAWARE LIMITED LIABILITY COMPANY)

              THESE MEMBERSHIP INTERESTS HAVE NOT BEEN REGISTERED
               UNDER THE SECURITIES ACT OF 1933, AS AMENDED, NOR
             PURSUANT TO THE PROVISIONS OF ANY STATE SECURITIES ACT

                 CERTAIN RESTRICTIONS ON TRANSFERS OF INTERESTS
                              ARE SET FORTH HEREIN

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                               TABLE OF CONTENTS
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ARTICLE I  Definitions............................................................................................1
ARTICLE II  Organization..........................................................................................5
         Section 2.1.               Formation.....................................................................5
         Section 2.2.               Name, Place of Business and Office............................................5
         Section 2.3.               Classification of the Company.................................................6
         Section 2.4.               Registered Office and Registered Agent........................................6
         Section 2.5.               Purposes and Character of Business; Powers....................................6
         Section 2.6.               Term..........................................................................6
ARTICLE III  Company Capital......................................................................................6
         Section 3.1.               Initial Capital Contributions of the Members..................................6
         Section 3.2.               Additional Capital Contributions of the Members...............................7
         Section 3.3.               Company Capital...............................................................7
         Section 3.4.               Liability of Members..........................................................7
         Section 3.5.               Loans by Members or Affiliates................................................8
         Section 3.6.               Capital Accounts..............................................................8
         Section 3.7.               Sharing Ratios................................................................9
ARTICLE IV  Manager...............................................................................................9
         Section 4.1.               Election......................................................................9
         Section 4.2.               Vacancies....................................................................10
         Section 4.3.               Powers of Manager............................................................10
         Section 4.4.               Transactions with Related Parties............................................10
         Section 4.5.               Indemnification of the Manager...............................................10
ARTICLE V  Allocations and Distributions.........................................................................11
         Section 5.1.               Distributions................................................................11
         Section 5.2.               Allocations of Profits and Losses............................................11
         Section 5.3.               Compliance with Code.........................................................14
         Section 5.4.               Allocations upon Transfer of Membership Interest.............................14
ARTICLE VI  Meetings of Members..................................................................................15
         Section 6.1.               Place of Meetings............................................................15
         Section 6.2.               Notice of Meetings of Members................................................15
         Section 6.3.               Quorum.......................................................................15
         Section 6.4.               Voting on Matters............................................................16
         Section 6.5.               List of Members Entitled to Vote.............................................16
         Section 6.6.               Actions With or Without a Meeting and Telephone Meetings.....................16
ARTICLE VII  Transferability of Member's Interest................................................................16
         Section 7.1.               Restrictions on Transfer of Interest of a Member.............................16
         Section 7.2.               Assignees....................................................................17
         Section 7.3.               Substituted Members..........................................................18
ARTICLE VIII  Books and Records; Accounting; Reporting; Tax Elections; Etc.......................................18
         Section 8.1.               Books and Records............................................................18
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         Section 8.2.               Accounting Basis for Tax Reporting Purposes; Fiscal Year.....................19
         Section 8.3.               Reports......................................................................19
         Section 8.4.               Tax Matters Partner..........................................................19
ARTICLE IX  Dissolution, Liquidation and Termination of the Membership...........................................19
         Section 9.1.               Events Causing Dissolution...................................................19
         Section 9.2.               Liquidation; Sale of Substantially all of the Assets.........................20
         Section 9.3.               Distributions in Kind........................................................20
ARTICLE X  Miscellaneous Provisions..............................................................................21
         Section 10.1.              Address for Notices..........................................................21
         Section 10.2.              Additional Documents and Acts................................................21
         Section 10.3.              Assumed Name.................................................................21
         Section 10.4.              Qualification in Foreign Jurisdictions.......................................21
         Section 10.5.              Application of Delaware Law..................................................21
         Section 10.6.              No Action for Partition......................................................22
         Section 10.7.              Headings and Sections........................................................22
         Section 10.8.              Amendment of Certificate of Formation and Agreement..........................22
         Section 10.9.              Numbers and Gender...........................................................22
         Section 10.10.             Binding Effect...............................................................22
         Section 10.11.             Counterparts.................................................................22
         Section 10.12.             Approvals....................................................................22

SCHEDULE 1                 Names, Addresses, Initial Capital Contributions, and Sharing Ratios of the Members
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                      LIMITED LIABILITY COMPANY AGREEMENT
                        OF HIGHWAYMASTER OF CANADA, LLC

         This Limited Liability Company Agreement of HighwayMaster of Canada,
LLC, is hereby duly adopted, approved, ratified, and confirmed as the Limited
Liability Company Agreement of HighwayMaster of Canada, LLC, a Delaware limited
liability company, effective as of the 3rd day of March, 2000, by the party
signing this Agreement as the initial Manager and Member of the Company.

         The Certificate of Formation of the Company, dated March 3, 2000, was
filed in the office of the Secretary of State of Delaware on March 3, 2000.

                                   ARTICLE I

                                  DEFINITIONS

         The definitions used in this Agreement shall, unless the context
otherwise requires, have the meanings specified in this Article.

         1. "ACT" means the Delaware Limited Liability Company Act, as amended
from time to time.

         2. "ADDITIONAL CAPITAL CONTRIBUTION" means any amount contributed or
deemed to be contributed to the capital of the Company by the Members pursuant
to Section 3.2.

         3. "ADJUSTED CAPITAL ACCOUNT" means, with respect to any Member, such
Member's Capital Account as of the end of any relevant date after giving effect
to the following adjustments:

                  (a) Credit to such Capital Account any amounts which such
Member is deemed to be obligated to restore pursuant to Treasury Regulations
Section 1.704-1(b)(2)(ii)(c), 1.704-2(g)(1) and 1.704-2(i)(5); and

                  (b) Debit to such Capital Account the items described in
Treasury Regulations Sections 1.704-1(b)(2)(ii)(d)(4), (5) and (6).

         The foregoing definition of "Adjusted Capital Account" is intended to
comply with the provisions of Treasury Regulations Section 1.704-1(b)(2)(ii)(d)
and 1.704-2, and shall be interpreted consistently therewith.

         4. "ADJUSTED CAPITAL ACCOUNT DEFICIT" means, with respect to any
Member, the deficit balance, if any, in that Member's Adjusted Capital Account.

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         5. "AFFILIATE" means any Person that directly, or indirectly through
one or more intermediaries, controls, is controlled by or is under common
control with the Person to whom reference is made. The term "control" as used
herein (including the terms "controlling," "controlled by," and "under common
control with") means the possession, direct or indirect, of the power (a) to
vote fifty percent (50%) or more of the outstanding voting securities of or
voting interest in a Person, or (b) otherwise to direct the management policies
of such Person by contract or otherwise.

         6. "AGREEMENT" means this Limited Liability Company Agreement, as
amended from time to time.

         7. "AVAILABLE FUNDS" means Company cash on hand, as of the date of
computation, including (without limitation) cash derived from any one or more
of the following sources: (a) the Capital Contributions of the Members made
pursuant to the terms of this Agreement, (b) the proceeds of any sale or other
disposition of all or any portion of the assets, including, but not limited to,
any insurance proceeds, and (c) all Company operating income.

         8. "BANKRUPT MEMBER" means any Member who is insolvent, who has filed
a voluntary petition in bankruptcy or against whom a third party has filed an
involuntary petition in bankruptcy and the same is not dismissed within thirty
(30) days.

         9. "BOOK VALUE" means, with respect to any asset, the asset's adjusted
basis for federal income tax purposes, except (a) the initial Book Value of any
asset contributed by a Member to the Company shall be the fair market value of
such asset, as determined by the Manager; (b) the Book Value of all Company
assets shall be adjusted in the event of a revaluation as provided in Section
3.6(d); (c) the Book Value of any Company asset distributed to any Member shall
be the fair market value of such asset on the date of distribution as
determined by the Manager; and (d) such Book Value shall be adjusted by the
Depreciation taken into account with respect to such asset for purposes of
computing Profits and Losses.

         10. "CAPITAL ACCOUNT" means with respect to any Member, the account
maintained for such Member in a manner which the Manager determines is in
accordance with Treasury Regulations Section 1.704-1(b)(2)(iv).

         11. "CAPITAL CONTRIBUTIONS" means the total of all capital
contributions of the Members pursuant to Sections 3.1 and 3.2, including, but
not limited to, the Initial Capital Contributions and the Additional Capital
Contributions.

         12. "CODE" means the Internal Revenue Code of 1986, as amended from
time to time.

         13. "COMPANY" means HighwayMaster of Canada, LLC, a Delaware limited
liability company.

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         14. "DEPRECIATION" means, for each Fiscal Year or other period, an
amount equal to the depreciation, amortization or other cost recovery deduction
allowable with respect to an asset for such year or other period, except that
if the Book Value of an asset differs from its adjusted basis for federal
income tax purposes at the beginning of such year or other period (as a result
of property contributions or adjustments to such values), Depreciation shall be
adjusted as necessary so as to be an amount which bears the same ratio to such
beginning Book Value as the federal income tax depreciation, amortization, or
other cost recovery deduction for such year or other period bears to such
beginning adjusted tax basis; provided, however, that if the federal income tax
depreciation, amortization, or other cost recovery deduction for such year or
other period is zero, Depreciation for such year or other period shall be
determined with reference to such beginning Book Value using any reasonable
method selected by the Manager.

         15. "DISTRIBUTABLE CASH FLOW" means any Available Funds not required
to meet current or anticipated obligations of the Company, as determined by the
Manager. In determining what cash is available for distribution, the Manager
may retain such amounts as the Manager in its sole discretion determine will be
required to pay the Company's debts, obligations and expenses, and to
accomplish the Company's goals and operating results, whether then accrued or
anticipated to accrue in the future.

         16. "FISCAL YEAR" means the fiscal year of the Company as established
in Section 8.2.

         17. "INITIAL CAPITAL CONTRIBUTION" means, as to any Member, any amount
contributed to the capital of the Company by a Member pursuant to Section 3.1.

         18. "MAJORITY" means, with respect to any referenced group of Members,
a combination of such Members who, in the aggregate, own more than fifty
percent (50%) of the Sharing Ratios owned by all of the Members included in
such referenced group, and, with respect to any other referenced group of
persons, more than fifty percent (50%) of the total number of such persons.

         19. "MANAGER" means any person or persons that are elected to act as
managers of the Company as provided herein. "MANAGERS" means all such persons
collectively in their capacity as Managers of the Company.

         20. "MEMBER" means the parties listed as Members on Schedule 1 of this
Agreement or any successor or successors to all or part of any such Member's
Membership Interest, or any party admitted as an additional member to the
Company in accordance with this Agreement and the Act, each in the capacity as
a Member of the Company. "MEMBERS" mean all such persons collectively in their
capacity as Members of the Company.

         21. "MEMBER NONRECOURSE DEBT" means any nonrecourse debt (as defined
in Treasury Regulations Section 1.704-2(b)(4)) of the Company for which any
Member bears the

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economic risk of loss, in accordance with Treasury Regulations Sections
1.704-2(b)(4) and 1.752-2.

         22. "MEMBER NONRECOURSE DEBT MINIMUM GAIN" means, for each Member, the
amount of Minimum Gain for the Fiscal year or other period attributable to such
Member's "partner nonrecourse debt," determined in accordance with Treasury
Regulations Section 1.704-2(i)(2).

         23. "MEMBER NONRECOURSE DEDUCTIONS" means any Losses or other losses
or deductions of the Company that must be allocated to a Member who bears the
economic risk of loss for the "partner nonrecourse liability" to which the
Losses or other losses or other deductions relate, determined in accordance
with Treasury Regulations Section 1.704-2(i)(1).

         24. "MEMBERSHIP INTEREST" means all of the rights and obligations of a
Member in respect of such Member's ownership interest in the Company, including
but not limited to the right to receive distributions and any obligation to
make Capital Contributions under this Agreement.

         25. "MINIMUM GAIN" means, with respect to all nonrecourse liabilities
of the Company, the minimum amount of gain that would be realized by the
Company if the Company disposed of the Company property subject to such
liability in full satisfaction thereof computed in accordance with Treasury
Regulations Section 1.704-2(d).

         26. "MINIMUM GAIN SHARE" means, for each Member, such Member's share
of Minimum Gain for the Fiscal Year (after taking into account any decrease in
Minimum Gain for such year), such share to be determined under Treasury
Regulations Section 1.704-2(g).

         27. "NONRECOURSE DEDUCTIONS" means, for each Fiscal Year or other
period, an amount of Company deductions that are characterized as "nonrecourse
deductions" under Treasury Regulations Section 1.704-2(c).

         28. "PERSON" OR "PERSON" means an individual, a corporation, a sole
proprietorship, a partnership, a limited liability company, an association, a
trust, a joint venture, or any other entity or organization, including a
government or political subdivision or an agency or instrumentality thereof.

         29. "PROFITS" and "LOSSES" means, for each Fiscal Year or other
period, an amount equal to the Company's taxable income or loss for such year
or period, determined in accordance with Code Section 703(a) (for this purpose,
all items of income, gain, loss, or deduction required to be stated separately
pursuant to Code Section 703(a)(1) shall be included in taxable income or
loss), with the following adjustments:

                  (a) Any income of the Company that is exempt from federal
income tax and not otherwise taken into account in computing Profits or Losses
pursuant to this definition shall be added to such taxable income or loss;

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                  (b) Any expenditures of the Company described in Code Section
705(a)(2)(B) or treated as Code Section 705(a)(2)(B) expenditures pursuant to
Treasury Regulations Section 1.704-1(b)(2)(iv)(i), and not otherwise taken into
account in computing Profits or Losses pursuant to this definition, shall be
subtracted from such taxable income or loss;

                  (c) Gain or loss resulting from any disposition of Company
property with respect to which gain or loss is recognized for federal income
tax purposes shall be computed by reference to the Book Value of the property
disposed of, notwithstanding that the adjusted tax basis of such property
differs from such Book Value;

                  (d) In lieu of the depreciation, amortization, and other cost
recovery deductions taken into account in computing such taxable income or
loss, there shall be taken into account Depreciation for such fiscal year or
other period, computed in accordance with the definition of "Depreciation"
herein; and

                  (e) Notwithstanding any other provision of this definition,
any items which are specifically allocated pursuant to Section 5.2(c) shall not
be taken into account in computing Profits or Losses.

         30. "SHARING RATIO" means, with respect to any Member, the percentage
assigned to such Member in accordance with Section 3.7, as such percentage may
change from time to time.

         31. "TREASURY REGULATIONS" means the Income Tax Regulations
promulgated under the Code, as such regulations may be amended from time to
time (including corresponding provisions of succeeding regulations).

                                  ARTICLE II

                                  ORGANIZATION

         SECTION 2.1. FORMATION

         The Company was formed upon the filing of the Certificate of Formation
of the Company on March 3, 2000, pursuant to the
Act.

         SECTION 2.2. NAME, PLACE OF BUSINESS AND OFFICE

         The name of the Company is HighwayMaster of Canada, LLC, although such
business may be conducted under any other name to the extent permitted by local
law. The Company shall maintain its principal office at the following address:
1155 Kas Drive, Suite 100, Richardson, Texas, 75081. The Manager may at any
time change the location of the Company's

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office and may establish additional offices, if it deems it advisable. The
Manager shall promptly give the Members written notice of any change in
location of the principal office of the Company.

         SECTION 2.3. CLASSIFICATION OF THE COMPANY

         Notwithstanding anything to the contrary contained herein, the Members
intend that the Company shall be classified as a corporation for federal tax
purposes and shall be subject to all federal tax laws governing corporations.
The Members intend that the Company not be a corporation for any purposes other
than federal tax purposes, and this Agreement may not be construed to suggest
otherwise.

         SECTION 2.4. REGISTERED OFFICE AND REGISTERED AGENT

         The Company's initial registered office shall be 1209 Orange Street,
Wilmington, Delaware 19801, and the name of its initial registered agent at
such address is The Corporation Trust Corporation.

         SECTION 2.5. PURPOSES AND CHARACTER OF BUSINESS; POWERS

         The purposes and character of the business of the Company are to
transact any or all lawful business for which limited liability companies may
be organized under the Act. The Company shall have any and all powers which are
necessary or desirable to carry out the purposes and business of the Company.

         SECTION 2.6. TERM

         The term of existence of the Company shall be perpetual, unless the
Company is earlier dissolved in accordance with either the provisions of this
Agreement or the Act.

                                  ARTICLE III

                                COMPANY CAPITAL

         SECTION 3.1. INITIAL CAPITAL CONTRIBUTIONS OF THE MEMBERS

                  (a) Upon the execution of this Agreement, the Members shall
contribute cash and/or property to the Company in the amount set forth as the
Initial Capital Contribution of such Member on Schedule 1 attached hereto and
hereby made a part hereof. Such cash shall be the Initial Capital Contribution
of each such Member and each such Member agrees to make its Initial Capital
Contribution.

                  (b) Upon making the initial Capital Contribution, the Members
shall receive its Membership Interest and its initial Sharing Ratio, as set
forth on Schedule 1.

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         SECTION 3.2. ADDITIONAL CAPITAL CONTRIBUTIONS OF THE MEMBERS

                  (a) A Member may make an optional Additional Capital
Contribution to the Company at any time at the request of and upon receiving
the consent of the Manager. No Member shall be required to make any Additional
Capital Contribution unless such Member consents thereto.

                  (b) If any Member makes a payment directly to a creditor or
another Member in satisfaction of any indebtedness of the Company pursuant to
any indemnity, guaranty or contribution obligation of such Member which has
been approved by the Manager in respect of Company indebtedness, or if any
collateral interest granted by such Member to such creditor or other Member
which has been approved by the Manager to secure any such indebtedness is
foreclosed and the proceeds of such foreclosure are applied to reduce or
satisfy such indebtedness and any foreclosure-related expenses, such Member
shall be deemed to have made a permitted Additional Capital Contribution equal
to such amount, shall receive a credit to its Capital Account in the amount
thereof.

         SECTION 3.3. COMPANY CAPITAL

                  (a) Except as may be otherwise specifically provided in this
Agreement, no Member shall be paid interest on any Capital Contribution to the
Company.

                  (b) No Member shall have the right to withdraw all or any
part of its Capital Contribution or to receive any return on any portion of its
Capital Contribution, except as may be otherwise specifically provided in this
Agreement.

                  (c) Under circumstances involving a return of any Capital
Contribution, no Member shall have the right to receive property other than
cash.

         SECTION 3.4. LIABILITY OF MEMBERS

                  (a) No Member shall be liable for the debts, liabilities,
contracts or any other obligation of the Company, except to the extent
expressly provided herein or in the Act. No Member shall be liable for the
debts or liabilities of any other Member.

                  (b) No Member shall be required to contribute to the capital
of, or loan, the Company any funds other than as expressly required in this
Agreement.

                  (c) The Manager shall not be liable for the return of all or
any portion of the Capital Contributions of any Member.

                  (d) Except as otherwise expressly provided herein, no Member
shall have any priority over any other Member as to the return of its
contributions to capital or as to compensation by way of income.

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         SECTION 3.5. LOANS BY MEMBERS OR AFFILIATES

         Any Member or Affiliate may (but shall not be obligated to) at any
time, upon obtaining the consent of the Manager, loan money or guarantee a loan
to the Company to finance Company operations, to finance or refinance any
assets of the Company, to pay the debts and obligations of the Company, or for
any other Company purpose. If any Member or its Affiliate lends funds or
guarantees a loan of funds to the Company, such Member or Affiliate shall be
entitled to receive interest on such loan, or a fee for guaranteeing any such
loan, at an interest rate or fee to be agreed upon by such Member or Affiliate
and the Manager.

         SECTION 3.6. CAPITAL ACCOUNTS

                  (a) A Capital Account shall be established and maintained for
each Member.

                  (b) A Member's Capital Account shall be credited with (i) the
amount of cash and the initial Book Value of any property contributed by such
Member to the Company as a Capital Contribution pursuant to Sections 3.1 or
3.2, (ii) such Member's allocable share of Profits, income and gain and (iii)
the amount of any Company liabilities that are expressly assumed by such Member
or that are secured by any Company property distributed to such Member.

                  (c) A Member's Capital Account shall be debited with (i) the
amount of cash and the Book Value of any Company property distributed to such
Member pursuant to any provision of this Agreement, (ii) such Member's
allocable share of Losses, deductions and other losses and (iii) the amount of
any liabilities of such Member that are expressly assumed by the Company or
that are secured by any property contributed by such Member to the Company.

                  (d) Upon the occurrence of certain events described in
Treasury Regulations Sections 1.704-1(b)(2)(iv)(f), 1.704-1(b)(4) and 1.704-2,
the Manager may elect to increase or decrease the Capital Accounts of the
Members to reflect a revaluation of Company property on the Company's books.

                  (e) The Capital Account of each Member shall be determined
after giving effect to all transactions which have been effected prior to the
time when such determination is made giving rise to the allocation of Profits
and Losses and to all contributions and distributions theretofore made. Any
person who acquires a Membership Interest directly from a Member, or whose
Sharing Ratio shall be increased by means of a transfer to it of all or part of
the interest of another Member, shall have a Capital Account which includes all
or part of the Capital Account balance of the Membership Interest so acquired
or transferred.

                  (f) In the event that any Member makes a loan to the Company,
such loan shall not be considered a contribution to the capital of the Company
and shall not increase the

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Capital Account of the lending Member. Repayment of such loans shall not be
deemed withdrawals from the capital of the Company.

                  (g) Any fees, salary or similar compensation payable to a
Member pursuant to this Agreement shall be deemed a guaranteed payment for
federal income tax purposes and not a distribution to such Member for such
purposes. Such payments to a Member shall not reduce the Capital Account of
such Member, except to the extent of its distributive share of any Company
Losses or other downward capital adjustment resulting from such payment.

                  (h) From time to time the Manager may make such modifications
to the manner in which the Capital Accounts are computed to comply with
Treasury Regulations Sections 1.704-1(b) and 1.704-2 provided that such
modification is not likely to have a material effect on the amounts
distributable to any Member pursuant to this Agreement.

                  (i) The foregoing provisions and the other provisions of this
Agreement relating to the maintenance of Capital Accounts are intended to
comply with Treasury Regulations Sections 1.704-1(b) and 1.704-2, and shall be
interpreted and applied in a manner consistent with such Treasury Regulations.

                  (j) No Member with a deficit balance in its Capital Account
shall have any obligation to the Company or any other Member to restore such
deficit balance. In addition, no venturer or partner in any Member shall have
any liability to the Company or any other Member for any deficit balance in
such venturer's or partner's capital account in the Member in which it is a
venturer or partner. Furthermore, a deficit Capital Account balance of a Member
(or a deficit capital account of a partner or venturer in a Member) shall not
be deemed to be a Company asset or Company property.

         SECTION 3.7. SHARING RATIOS

         The initial Sharing Ratio of each Member is set forth opposite its
respective name on Schedule 1, attached hereto and hereby made a part of this
Agreement.

                                  ARTICLE IV

                                    MANAGER

         SECTION 4.1. ELECTION

         The Manager of the Company shall be HighwayMaster Communications, Inc.
and HighwayMaster Communications, Inc. shall remain as Manager of the Company
until the earlier of (1) HighwayMaster Communications, Inc.'s resignation as
Manager or (2) the dissolution of the Company in accordance with this
Agreement.

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         SECTION 4.2. VACANCIES

         Any vacancy occurring in the office of the Manager may be filled by
the affirmative vote of all of the Members.

         SECTION 4.3. POWERS OF MANAGER

         To the fullest extent permitted by applicable law, the Manager shall
have full, exclusive and complete discretion to manage and control the affairs
of the Company, shall make all decisions affecting the Company business, shall
have full authority to take any action contemplated hereby and shall have full
power to exercise any and all rights generally inferred or conferred by law in
connection therewith.

         SECTION 4.4. TRANSACTIONS WITH RELATED PARTIES

         The Manager may agree, contract, or arrange with the Manager, any
Member or any Affiliates of any Manager or Member in the name and on behalf of
the Company, for the performance of services for the Company, and the payment
of compensation therefor, in carrying out the business of the Company as if
such Manager, Member or Affiliate were an independent contractor, provided that
the compensation for such services shall be (a) at rates comparable to the
charges made to the third parties for rendering comparable services in the
geographical area where the services are performed and (b) paid only for actual
services rendered to the Company.

         SECTION 4.5. INDEMNIFICATION OF THE MANAGER

                  (a) To the fullest extent allowed by the Act and other
applicable law, the Company shall indemnify, defend against and save harmless
the Manager from, any expenses (including reasonable attorneys' fees and court
costs), liabilities, claims, causes of action, losses or damages incurred by
reason of any act or omission performed or omitted by the Manager in good faith
on behalf of the Company or the Members and in a manner reasonably believed by
such Manager to be within the scope of the authority granted to it by this
Agreement, REGARDLESS OF WHETHER SUCH ACT OR OMISSION CONSTITUTED THE SOLE,
PARTIAL OR CONCURRENT NEGLIGENCE (WHETHER ACTIVE OR PASSIVE) OF SUCH MANAGER.

                  (b) The satisfaction of any indemnification under this
Section shall be from and limited to Company assets, including insurance
proceeds, if any, and no Member shall have any personal liability on account
thereof.

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                                   ARTICLE V

                         ALLOCATIONS AND DISTRIBUTIONS

         SECTION 5.1. DISTRIBUTIONS

                  (a) First, to the Members, at such times as the Manager shall
determine, in respect of each Member's accrued and unpaid Additional Capital
Contributions, in the proportion that such Member's accrued and unpaid
Additional Capital Contributions bears to the sum of all Members' accrued and
unpaid Additional Capital Contributions; and

                  (b) Then the balance to the Members, pro rata, at such times
as the Manager shall determine, in accordance with such Members' respective
Sharing Ratios, determined as of the date of distribution.

         SECTION 5.2. ALLOCATIONS OF PROFITS AND LOSSES

                  (a) TREATMENT AS A CORPORATION. Notwithstanding anything
contained in Article 5, for federal tax purposes, the Company is classified as
a corporation which recognizes Profits and Losses at the Company level instead
of allocating such Profits and Losses to the Members. Except as provided in the
preceding sentence, for all purposes and in the event the Company is classified
as a partnership for federal tax purposes, the Profits and Losses are subject
to the allocation provisions as provided in Sections 5.2(b) through 5.2(h)
below.

                  (b) PROFITS. Except as provided in Sections 5.2(a), 5.2(d)
and 5.2(e), Profits for any Fiscal Year will be allocated in the following
order:

                           (1) First, to each Member until the cumulative
Profits allocated to such Member under this Section 5.2(b)(1) equals the
cumulative Losses allocated to such Member under Section 5.2(c)(2) for all
prior periods; and

                           (2) The balance, if any, to the Members in
proportion to their respective Sharing Ratios.

                  (c) LOSSES. Except as provided in Section 5.2(d) and 5.2(e),
Losses for any Fiscal Year will be allocated in the following order:

                           (1) First, to each Member until the cumulative
Losses allocated to such Member under this Section 5.2(c)(1) equals the
cumulative Profits allocated to such Member under Section 5.2(b)(2) for all
prior periods; and

                           (2) The balance, if any, to the Members in
proportion to their respective Sharing Ratios.

                                      11
<PAGE>   15

                  (d) SPECIAL ALLOCATIONS. Except as otherwise provided in
Section 5.2(a), the following special allocations will be made in the following
order and priority:

                           (1) MEMBER MINIMUM GAIN CHARGEBACK. Notwithstanding
any other provision of this Section (other than Section 5.2(a), which shall be
controlling over this Section 5.2(d)(1)), if there is a net decrease in Company
Minimum Gain during any taxable year or other period for which allocations are
made, the Members will be specially allocated items of Company income and gain
for that period (and, if necessary, subsequent periods). The amount allocated
to each Member under this Section 5.2(d)(1) shall be an amount equal to such
Member's share of the net decrease in Company Minimum Gain during such year or
other period determined in accordance with Treasury Regulations Section
1.704-2(g)(2). This Section 5.2(d)(1) is intended to comply with the
"partnership minimum gain chargeback" requirements of the Treasury Regulations
and the exceptions thereto and will be interpreted consistently therewith.

                           (2) MEMBER NONRECOURSE DEBT MINIMUM GAIN CHARGEBACK.
Notwithstanding any other provision of this Section (other than Section 5.2(a),
which shall be controlling over this Section 5.2(d)(2) and Section 5.2(d)(1),
which shall be applied first), if there is a net decrease in Member Nonrecourse
Debt Minimum Gain during any taxable year or other period for which allocations
are made, any Member with a share of such Member Nonrecourse Debt Minimum Gain
attributable to such Member Nonrecourse Debt (determined under Treasury
Regulations Section 1.704-(2)(i)(5)) as of the beginning of the year shall be
specially allocated items of Company income and gain for that period (and, if
necessary, subsequent periods) in proportion to the portion of such Member's
share of the net decrease in the Member Nonrecourse Debt Minimum Gain with
respect to such Member Nonrecourse Debt that is allocable to the disposition of
Company property subject to such Member Nonrecourse Debt. The items to be so
allocated shall be determined in accordance with Regulations Section
1.704-2(g). This Section is intended to comply with the "partner nonrecourse
debt minimum gain chargeback" requirements of the Treasury Regulations and the
exceptions thereto and shall be interpreted consistently therewith.

                           (3) QUALIFIED INCOME OFFSET. A Member who
unexpectedly receives any adjustment, allocation or distribution described in
Treasury Regulations Sections 1.704-1(b)(2)(ii)(d)(4), (5) or (6) will be
specially allocated items of Company income and gain in an amount and manner
sufficient to eliminate, to the extent required by the Treasury Regulations,
the Adjusted Capital Account Deficit of the Member as quickly as possible.

                           (4) NONRECOURSE DEDUCTIONS. Nonrecourse Deductions
for any taxable year or other period for which allocations are made will be
allocated among the Members in proportion to their respective Sharing Ratios in
the Company.

                           (5) MEMBER NONRECOURSE DEDUCTIONS. Notwithstanding
anything to the contrary in this Agreement (other than Section 5.2(a), which
shall be controlling over this Section 5.2(d)(5)), any Member Nonrecourse
Deductions for any taxable year or other period for which allocations are made
will be allocated to the Member who bears the economic risk of

                                      12
<PAGE>   16

loss with respect to the Member Nonrecourse Debt to which the Member
Nonrecourse Deductions are attributable in accordance with Treasury Regulations
Section 1.704-2(i).

                           (6) CODE SECTION 754 ADJUSTMENTS. To the extent an
adjustment to the adjusted tax basis of any Company asset under Code Sections
734(b) or 743(b) is required to be taken into account in determining Capital
Accounts under Treasury Regulations Section 1.704-1(b)(2)(iv)(m), the amount of
the adjustment to the Capital Accounts will be treated as an item of gain (if
the adjustment increases the basis of the asset) or loss (if the adjustment
decreases the basis), and the gain or loss will be specially allocated to the
Members in a manner consistent with the manner in which their Capital Accounts
are required to be adjusted under Treasury Regulations Section
1.704-1(b)(2)(iv)(m).

                           (7) DEPRECIATION RECAPTURE. In the event there is
any recapture of Depreciation or investment tax credit, the allocation of gain
or income attributable to such recapture shall be shared by the Members in the
same proportion as the deduction for such Depreciation or investment tax credit
was shared.

                           (8) INTEREST IN COMPANY. Notwithstanding any other
provision of this Agreement (other than Section 5.2(a), which shall be
controlling over this Section 5.2(d)(8)), no allocation of Profit or Loss or
item of Profit or Loss will be made to a Member if the allocation would not
have "economic effect" under Treasury Regulations Section 1.704-1(b)(2)(ii) or
otherwise would not be in accordance with the Member's interest in the Company
within the meaning of Treasury Regulations Section 1.704-1(b)(3) or
1.704-1(b)(4)(iv). The Manager will have the authority to reallocate any item
in accordance with this Section 5.2(d)(8).

                  (e) CURATIVE ALLOCATIONS. The allocations set forth in
Sections 5.2(d)(1) through (8) (the "Regulatory Allocations") are intended to
comply with certain requirements of Treasury Regulations Section 1.704-1(b) and
1.704-2. The Regulatory Allocations may not be consistent with the manner in
which the Members intend to divide Company distributions. Accordingly, the
Manager is authorized to further allocate Profits, Losses, and other items
among the Members so as to prevent the Regulatory Allocations from distorting
the manner in which Company distributions would be divided among the Members
under Sections 5.1 and 9.2 but for application of the Regulatory Allocations.
In general, the reallocation will be accomplished by specially allocating other
Profits, Losses and items of income, gain, loss and deduction, to the extent
they exist, among the Members so that the net amount of the Regulatory
Allocations and the special allocations to each Member is zero. The Manager
will have discretion to accomplish this result in any reasonable manner that is
consistent with Code Section 704 and the related Treasury Regulations.

                  (f) TAX ALLOCATIONS--CODE SECTION 704(C). In accordance with
Code Section 704(c) and the related Treasury Regulations, income, gain, loss
and deduction with respect to any property contributed to the capital of the
Company, solely for tax purposes, will be allocated among the Members so as to
take account of any variation between the adjusted basis to the Company of the
property for federal income tax purposes and the initial Book Value. If

                                      13
<PAGE>   17

the Book Value of any Company asset is adjusted, subsequent allocations of
income, gain, loss and deduction with respect to that asset will take account
of any variation between the adjusted basis of the asset for federal income tax
purposes and its Book Value in the same manner as under Code Section 704(c) and
the related Treasury Regulations. Any elections or other decisions relating to
allocations under this Section 5.2(f) will be made in any manner that the
Manager determines reasonably reflects the purpose and intention of this
Agreement. Allocations under this Section are solely for purposes of federal,
state and local taxes and will not affect, or in any way be taken into account
in computing, any Member's Capital Account or share of Profits, Losses or other
items or distributions under any provision of this Agreement.

                  (g) OTHER ALLOCATION RULES. The following rules will apply to
the calculation and allocation of Profits, Losses and other items:

                           (1) Except as otherwise provided in the Agreement,
all Profits, Losses and other items allocated to the Members will be allocated
among them in proportion to their Sharing Ratios.

                           (2) For purposes of determining the Profits, Losses
or any other item allocable to any period, Profits, Losses and other items will
be determined on a daily, monthly or other basis, as determined by the Manager
using any permissible method under Code Section 706 and the related Treasury
Regulations.

                           (3) Except as otherwise provided in this Agreement,
all items of Company income, gain, loss, deduction, credit and other
allocations not provided for in this Agreement will be divided among the
Members in the same proportions as they share Profits and Losses.

                  (h) MEMBER ACKNOWLEDGMENT. The Members agree to be bound by
the provisions of this Section in reporting their shares of Company income and
loss for income tax purposes.

         SECTION 5.3. COMPLIANCE WITH CODE

         The foregoing provisions of this Article relating to the allocation of
Profits, Losses and other items for federal income tax purposes are intended to
comply with Treasury Regulations Sections 1.704-1(b) and 1.704-2, and shall be
interpreted and applied in a manner consistent with such Treasury Regulations.
Notwithstanding anything to the contrary, nothing in this Article shall apply
if it lacks "economic effect."

         SECTION 5.4. ALLOCATIONS UPON TRANSFER OF MEMBERSHIP INTEREST

         Profits or Losses attributable to any Membership Interest which has
been transferred during any Company Fiscal Year shall be allocated between the
transferor and the transferee as follows:

                                      14
<PAGE>   18

                  (a) For the days in such Fiscal Year prior to and including
the date of the transfer, to the transferor.

                  (b) For the days in such Fiscal Year subsequent to the date
of the transfer, to the transferee.

                                  ARTICLE VI

                              MEETINGS OF MEMBERS

         SECTION 6.1. PLACE OF MEETINGS

         All meetings of the Members shall be held at the principal office of
the Company or at such other place within or without the State of Delaware as
may be determined by the Manager and set forth in the respective notice or
waivers of notice of such meeting. There shall be no annual meeting and a
meeting of the Members shall only take place at such time and in such manner as
the Manager determines.

         SECTION 6.2. NOTICE OF MEETINGS OF MEMBERS

         Written or printed notice stating the place, day and hour of the
meeting and the purpose or purposes for which the meeting is called, shall be
delivered not less than ten (10) nor more than sixty (60) days before the date
of the meeting, either personally or by mail, by or at the direction of the
Manager or person calling the meeting, to each Member of record entitled to
vote at such meeting. If mailed, such notice shall be deemed to be delivered
when deposited in the United States mail addressed to the Member at his address
as it appears on the transfer records of the Company, with postage prepaid.

         SECTION 6.3. QUORUM

         A Majority of the Members shall constitute a quorum at all meetings of
the Members, except as otherwise provided by law or the Certificate of
Formation. Once a quorum is present at the meeting of the Members, the
subsequent withdrawal from the meeting of any Member prior to adjournment or
the refusal of any Member to vote shall not affect the presence of a quorum at
the meeting. If, however, such quorum shall not be present at any meeting of
the Members, the Members entitled to vote at such meeting shall have the power
to adjourn the meeting from time to time, without notice other than
announcement at the meeting, until the holders of the requisite amount of
Membership Interests shall be present or represented. At any meeting of the
Members at which a quorum is present, the vote of the holders of a Majority of
all the Sharing Ratios owned by the Members present or represented at such
meeting shall be the act of the Members, unless the vote of a greater number is
required by law, the Certificate of Formation or this Agreement.

                                      16
<PAGE>   19

         SECTION 6.4. VOTING ON MATTERS

         For purposes of voting on matters other than a matter for which the
affirmative vote of the holders of a specified portion of the Membership
Interests entitled to vote is required by the Act, the Certificate of Formation
or this Agreement, at any meeting of the Members at which a quorum is present,
the act of the Members shall be the affirmative vote of the holders of a
Majority of the Sharing Ratios owned by the Members present or represented at
such meeting.

         SECTION 6.5. LIST OF MEMBERS ENTITLED TO VOTE

         The Manager shall make, at least five (5) days before each meeting of
Members, a complete list of the Members entitled to vote at such meeting, or
any adjournment of such meeting, arranged in alphabetical order, with the
address of and the Sharing Ratio held by each, which list, for a period of five
(5) days prior to such meeting, shall be kept on file at the registered office
of the Company and shall be subject to inspection by any Member at any time
during usual business hours. Such list shall also be produced and kept open at
the time and place of the meeting and shall be subject to inspection of any
Member during the whole time of the meeting. However, failure to comply with
the requirements of this Section shall not affect the validity of any action
taken at such meeting.

         SECTION 6.6. ACTIONS WITH OR WITHOUT A MEETING AND TELEPHONE MEETINGS

         Notwithstanding any provision contained in this Agreement, all actions
of the Members provided for herein shall be taken either at a meeting and
evidenced by written minutes thereof executed by an authorized Member or by
written consent without a meeting. Any meeting of the Members may be held by
means of a telephone conference in which all Members can hear each other. Any
action which may be taken by the Members without a meeting shall be effective
only if the written consent (or consents) sets forth the action so taken, and
is signed by the Members owning Sharing Ratios constituting not less than the
minimum number of Sharing Ratios that would be necessary to take such action if
all of the Members entitled to vote on the action were present and voted
thereon.

                                  ARTICLE VII

                      TRANSFERABILITY OF MEMBER'S INTEREST

         SECTION 7.1. RESTRICTIONS ON TRANSFER OF INTEREST OF A MEMBER

                  (a) Unless the Manager consents, no Member shall withdraw or
retire from the Company, substitute any person in its stead or sell, exchange,
transfer, give, assign, pledge, hypothecate, mortgage or dispose of all or any
portion of its Membership Interest. Any such prohibited sale, exchange,
transfer, gift, assignment, pledge, hypothecation, mortgage or disposition
shall be void and shall result in an automatic dissolution of the Company
subject to

                                      16
<PAGE>   20

the provisions of Section 9.1; provided, however, that a Member may transfer
his, her, or its Membership Interest to an Affiliate of such Member.

                  (b) Notwithstanding anything to the contrary contained
herein, unless all of the Members shall consent, no Member may sell, transfer
or assign all or any portion of its Membership Interest if such sale, transfer
or assignment would violate any federal securities laws or any applicable state
securities laws (including suitability standards).

         SECTION 7.2. ASSIGNEES

                  (a) The Company shall not recognize for any purpose any
purported sale, assignment or transfer of all or any fraction of the interest
of a Member unless the provisions of this Article have been satisfied, all
costs of such assignment have been paid by the assigning Member, such sale,
assignment or transfer is exempt from registration under the Securities Act of
1933, as amended, the Delaware Securities Act, as amended, and any other
applicable state of federal securities act, and there is delivered to the
Manager, upon request of the Manager, an opinion of counsel acceptable to the
Manager with respect thereto, and there is filed with the Company a written and
dated notification of such sale, assignment or transfer, in form satisfactory
to the Manager, executed and acknowledged by both the seller, assignor or
transferor and the purchaser, assignee or transferee and such notification (1)
contains the acceptance by the purchaser, assignee or transferee of and
agreement to be bound by all the terms and provisions of this Agreement and (2)
represents that such sale, assignment or transfer was made in accordance with
all applicable securities laws and regulations (including suitability
standards). Any sale, assignment or transfer shall be recognized by the Company
as effective on the date of such notification if the date of such notification
is within fifteen (15) days of the date on which such notification is filed
with the Company, and otherwise shall be recognized as effective on the date
such notification is filed with the Company.

                  (b) Any Member who assigns all its interest in the Company
shall cease to be a Member, except that, unless and until a substituted Member
has been admitted into the Company, such assigning Member shall retain the
statutory rights of the assignor of a Member's interest under the Act;
provided, however, that such assigning Member shall have no right to vote on,
consent to or approve any matter or decision (it being intended that the
Sharing Ratio of such assigning Member shall be ignored in determining whether
the requisite vote, consent or approval of the Members has been obtained).

                  (c) A person who is the assignee of all or any fraction of
the interest of a Member, but does not become a substituted Member, and desires
to make a further assignment of such interest, shall be subject to all the
provisions of this Article to the same extent and in the same manner as any
Member desiring to make an assignment of its interest.

                                      17
<PAGE>   21

         SECTION 7.3. SUBSTITUTED MEMBERS

                  (a) No Member shall have the right to substitute in its place
a purchaser, assignee, transferee, donee, heir, legatee, or other recipient of
all or any portion of the Membership Interest of such Member. Any such
purchaser, assignee, transferee, donee, legatee, distributee or other recipient
of an interest shall be admitted to the Company as a substituted Member only
with the consent of Members owning a Majority of the Sharing Ratios owned by
all of such other Members, which consent may be granted or withheld by any
Member in its sole discretion.

                  (b) No person shall become a substituted Member until such
person has satisfied the requirements of this Article; provided, however, that
for the purpose of allocating Profits, Losses and other items and distributing
cash available for distribution, a person shall be treated as having become,
and as appearing in the records of the Company as, a Member, as the case may
be, on such date as the sale, assignment or transfer to such person was
recognized by the Company pursuant to Section 7.2.

                  (c) Any purchaser, assignee, transferee, donee, heir, legatee
or other recipient of all or any portion of a Membership Interest who is not
admitted to the Company as a substituted Member (1) shall be entitled only to
allocations and distributions with respect to such Membership Interest in
accordance with this Agreement, (2) shall not have any right to vote on,
consent to or approve any matter or decision (it being intended that the
Sharing Ratio of such person shall be ignored for purposes of determining
whether the requisite vote, consent or approval of the Members has been
obtained), (3) shall not have any other rights of a Member under the Act or
this Agreement, except as expressly provided in this Section 7.3(c), but (4)
shall be subject to all of the duties and obligations of a Member under this
Agreement, the Certificate of Formation of the Company and applicable law,
including but not limited to, the provisions of Article 7 to the same extent
and in the same manner as any Member.

                                 ARTICLE VIII

         BOOKS AND RECORDS; ACCOUNTING; REPORTING; TAX ELECTIONS; ETC.

         SECTION 8.1. BOOKS AND RECORDS

         The books and records of the Company shall be maintained by the
Manager at the principal office of the Company and shall be available for
examination at such office by any Member or its duly authorized representatives
during regular business hours. Any Member, at its own expense, may cause an
audit of the books and records of the Company during regular business hours and
shall furnish a written report thereof to the other Members.

                                      18
<PAGE>   22
         SECTION 8.2. ACCOUNTING BASIS FOR TAX REPORTING PURPOSES; FISCAL YEAR

         The books and records of the Company shall be kept on such method of
reporting for tax and financial reporting purposes as the Manager shall select.
The Fiscal Year of the Company shall be the calendar year.

         SECTION 8.3. REPORTS

         Within ninety (90) days after the end of each Fiscal Year, the Manager
shall cause the Company to send to each Member a copy of each federal and, if
applicable, state income tax return of the Company for the Fiscal Year that
ended, together with such other tax information as shall be reasonably
necessary for the preparation by each Member of its federal and state income
tax returns.

         SECTION 8.4. TAX MATTERS PARTNER

         In the event the Company is treated as a partnership for federal tax
purposes, HighwayMaster Communications, Inc. shall act as the "tax matters
partner" pursuant to Section 6231(a)(7) of the Code.

                                  ARTICLE IX

           DISSOLUTION, LIQUIDATION AND TERMINATION OF THE MEMBERSHIP

         SECTION 9.1. EVENTS CAUSING DISSOLUTION

                  (a) The Company shall be dissolved upon the first of the
following to occur:

                           (1) upon the unanimous written agreement of all of
the Members;

                           (2) upon the election of the Manager;

                           (3) the entry of a judgment, order or decree of a
court of competent jurisdiction adjudicating the Company to be a bankrupt, and
the expiration without appeal of the period, if any, allowed by applicable law
in which to appeal therefrom; or

                           (4) the entry of a decree of judicial dissolution
under the Act.

                  (b) The events set forth in Section 9.1(a) constitute the
only means by which a dissolution of the Company shall occur.

                  (c) Upon dissolution of the Company, the business and affairs
of the Company shall terminate, and the assets of the Company shall be
liquidated under this Article 9.

                                      19
<PAGE>   23

                  (d) Dissolution of the Company shall be effective as of the
day on which the event occurs giving rise to the dissolution, but the Company
shall not terminate until there has been a winding up of the Company's business
and affairs, and the assets of the Company have been distributed as provided in
Section 9.2.

         SECTION 9.2. LIQUIDATION; SALE OF SUBSTANTIALLY ALL OF THE ASSETS

                  (a) Subject to the restrictions and limitations contained in
this Agreement, upon dissolution of the Company, the Manager may cause any part
or all of the Company assets to be sold in such manner as the Manager shall
determine in an effort to obtain the best prices for such assets (provided,
however, that the Manager may distribute Company assets in kind to the Members
to the extent practicable). During the liquidation period, the Manager shall
have the right to continue to operate and otherwise to deal with Company
property to the same extent the Manager has such right prior to dissolution of
the Company. In the event that the sole remaining Manager has dissolved,
withdrawn or becomes bankrupt or legally incapacitated, the Members may, within
thirty (30) days after any such occurrence, appoint a person to perform the
functions of the Manager in liquidating the assets of the Company and winding
up its affairs.

                  (b) In settling accounts after dissolution, the assets of the
Company shall be paid or distributed in the following order:

                           (1) first, to third party creditors, in the order of
priority as provided by law;

                           (2) then, to the Members and their respective
Affiliates for any fees or other compensation or any unreimbursed costs and
expenses owing to the Members or their respective Affiliates, and then to the
repayment of any loans with interest, made by any Member to the Company;

                           (3) then, an amount equal to the then remaining
positive balances in the Capital Accounts of the Members shall be distributed
to the Members in proportion to the amount of such balances; and

                           (4) then, any remainder shall be distributed to the
Members, pro rata, in accordance with their respective Sharing Ratios.

         Notwithstanding the foregoing, no distributions shall be made pursuant
to this Section 9.2 before giving effect to the allocations of Profits, Losses
and other items, pursuant to Section 5.2.

         SECTION 9.3. DISTRIBUTIONS IN KIND

         If any assets of the Company are distributed in kind pursuant to this
Agreement, such assets shall be distributed to the Members entitled thereto as
tenants-in-common in the same proportions as the Members would have been
entitled to cash distributions if such property had been sold for cash at its
fair market value and the net proceeds thereof distributed to the Members. In
the event that distributions in kind are made to the Members upon dissolution
and liquidation of the Company, the Capital Account balances of such Members
shall be adjusted to reflect the Members' allocable share of gain or loss which
would have resulted if the distributed property had

                                      20
<PAGE>   24

been sold at its fair market value (as determined in accordance with the method
for determining Book Value).

                                   ARTICLE X

                            MISCELLANEOUS PROVISIONS

         SECTION 10.1. ADDRESS FOR NOTICES

         All notices, demands, consents and reports provided for in this
Agreement shall be in writing and shall be given to the parties at the
addresses set forth herein or at such other addresses as the Members may
hereafter specify in writing. Such notices may be delivered by hand, or by
telex, telegram, facsimile or telecopy, or may be mailed, postage prepaid, by
certified or registered mail, by a deposit in a depository for the receipt of
mail regularly maintained by the United States Postal Service. All notices
which are hand delivered or given by telex, telegram, facsimile or telecopy
shall be deemed given on the date of delivery. Except as otherwise provided
herein, all notices which are mailed in the manner provided above shall be
deemed given three (3) days after being mailed.

         SECTION 10.2. ADDITIONAL DOCUMENTS AND ACTS

         In connection with this Agreement, as well as all transactions
contemplated by this Agreement, the Members agree to execute such additional
documents and papers, and to perform and do such additional acts as may be
necessary and proper to effectuate and carry out all of the provisions of this
Agreement.

         SECTION 10.3. ASSUMED NAME

         The Manager shall execute and file all assumed name certificates
required by applicable law.

         SECTION 10.4. QUALIFICATION IN FOREIGN JURISDICTIONS

         The Manager shall take such steps as are necessary or desirable to
allow the Company to conduct business in any jurisdiction where the Company
desires to conduct business.

         SECTION 10.5. APPLICATION OF DELAWARE LAW

         This Agreement and the application or interpretation hereof, shall be
governed exclusively by the laws of the State of Delaware, and specifically the
Act.

                                      21
<PAGE>   25

         SECTION 10.6. NO ACTION FOR PARTITION

         No Member shall have any right to maintain any action for partition
with respect to the property of the Company.

         SECTION 10.7. HEADINGS AND SECTIONS

         The headings in this Agreement are inserted for convenience only and
are in no way intended to describe, interpret, define, or limit the scope,
extent or intent of this Agreement or any provision hereof. Unless the context
requires otherwise, all references in this Agreement to Sections or Articles
shall be deemed to mean and refer to Sections or Articles of this Agreement.

         SECTION 10.8. AMENDMENT OF CERTIFICATE OF FORMATION AND AGREEMENT

         Except as otherwise expressly set forth in this Agreement, the
Certificate of Formation of the Company and this Agreement may be amended,
supplemented or restated at any time by the Manager as it determines in its
sole discretion.

         SECTION 10.9. NUMBERS AND GENDER

         Where the context so indicates, the masculine shall include feminine
and neuter, and the neuter shall include the masculine and feminine, and the
singular shall include the plural.

         SECTION 10.10. BINDING EFFECT

         Except as herein otherwise provided to the contrary, this Agreement
shall be binding upon and inure to the benefit of the Members, their
distributees, heirs, legal representatives, executors, administrators,
successors and assigns.

         SECTION 10.11. COUNTERPARTS

         This Agreement may be executed in multiple counterparts, each of which
shall be deemed to be an original and shall be binding upon the Member who
executed the same, but all of such counterparts shall constitute the same
Agreement.

         SECTION 10.12. APPROVALS

         Except where otherwise indicated, all approvals, consents and other
similar rights of the Members or Manager, or of any portion of the Members or
Manager, pursuant to this Agreement may be exercised by such Members or
Manager, and such approvals and consents may be granted or denied by such
Members or Manager, in their sole and absolute discretion.

                                      22
<PAGE>   26

         IN WITNESS WHEREOF, the undersigned, being the sole Member and Manager
of the Company named in the Certificate of Formation of the Company has caused
this Agreement to be duly adopted by the Company effective as of the day first
above written.

MANAGER:                                    MEMBER:

HIGHWAYMASTER                               HIGHWAYMASTER
COMMUNICATIONS, INC., a                     COMMUNICATIONS, INC., a
Delaware corporation                        Delaware corporation

By: /S/ JANA BELL                           By: /S/ JANA BELL
   ---------------------------                  --------------------------------
Name: JANA BELL                             Name: JANA BELL
      ------------------------                    ------------------------------
Its: PRESIDENT & CEO                        Its: PRESIDENT & CEO
     -------------------------                   -------------------------------

<PAGE>   27

                                   SCHEDULE 1

  Name, Address, Initial Capital Contribution and Sharing Ratio of the Member

<TABLE>
<CAPTION>

Name and Address:                           Initial Capital Contribution               Sharing Ratio
----------------                            ----------------------------               -------------

<S>                                         <C>                                         <C>
HighwayMaster Communications, Inc.                   $1,000.00                             100%
1155 Kas Drive, Suite 100
Richardson, Texas 75081
</TABLE><PAGE>   1
                                                                   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").

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 1
<PAGE>   2

                                    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.

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 2
<PAGE>   3

         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

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 3
<PAGE>   4

                           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.

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 4
<PAGE>   5

                  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.

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 5
<PAGE>   6
                                    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

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 6
<PAGE>   7

         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

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 7
<PAGE>   8

         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

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 8
<PAGE>   9

         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.

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 9
<PAGE>   10

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.

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 10
<PAGE>   11

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.

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 11
<PAGE>   12

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
      ---------------------------                 ---------------------------

INVESTOR RELATIONS SERVICES AGREEMENT - PAGE 12

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