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                                                                   EXHIBIT 10.36

                        ADMINISTRATIVE CARRIER AGREEMENT

         THIS ADMINISTRATIVE CARRIER AGREEMENT (the "Agreement") is entered into
by and between HighwayMaster Corporation ("HighwayMaster"), a Delaware
corporation, with its principal place of business located at 1155 Kas Drive,
Richardson, Texas, 75081, and Southwestern Bell Mobile Systems, Inc., a Virginia
and Delaware corporation ("SBMS"), with its principal place of business located
at 17330 Preston Road, Suite 100A, Dallas, Texas 75252, effective as of March
30, 1999.

         WHEREAS, HighwayMaster has previously engaged, and through the Cutover
Date will engage, GTE Wireless, Inc. ("GTEW") to provide administrative and
billing services to HighwayMaster in connection with HighwayMaster's provision
of enhanced services to its end users; and

         WHEREAS, HighwayMaster and GTEW have agreed that HighwayMaster will
engage a new provider of administrative and billing services; and

         WHEREAS, HighwayMaster desires to engage SBMS and SBMS desires to
provide to HighwayMaster certain administrative and billing services in
connection with HighwayMaster's provision of enhanced services to
HighwayMaster's end users;

         NOW, THEREFORE, in consideration of the premises, the terms and
conditions set forth herein, the mutual benefits to be gained by the performance
thereof and other good, valuable, mutual and binding consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties agree as follows:

                             I. DEFINITION OF TERMS

1.       The definition of terms set forth in this Section 1 shall apply in this
         Agreement (in addition to terms expressly defined elsewhere herein)
         including any and all exhibits, addenda, and amendments made to or
         incorporated herein now or in the future:

         1.1.     "Affiliate" means any person or entity that directly or
                  indirectly, through one or more intermediaries, controls, is
                  controlled by or is under common control with another person
                  or entity. Control shall be defined as (i) fifty percent (50%)
                  or more ownership or beneficial interest of income and capital
                  of an entity; or (ii) ownership of at least fifty percent
                  (50%) of the voting power of voting equity; or (iii) sole or
                  shared management by a general partner of the entity; or (iv)
                  the ability to otherwise direct management policies of the
                  entity by contract or otherwise.

         1.2.     "BID" means the billing identification code that allows an
                  NPA/NXX in a Market to be defined as a stand alone billing
                  center.

         1.3.     "Carrier" means a company authorized by appropriate regulatory
                  agencies to provide

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                  domestic cellular radio service.

         1.4.     "Cellular Number or MIN" means the phone number or mobile
                  identification number assigned to a Unit.

         1.5.     "Covered Markets" means those Markets operated by Carriers
                  with which SBMS has both an Intercarrier Roamer Service
                  Agreement ("IRSA") and Addendum to IRSA for HighwayMaster
                  Service, and with which HighwayMaster has a Cellular Service
                  Agreement ("CSA").

         1.6.     "CTS" means cellular telephone service available in any
                  Covered Market.

         1.7.     "CTS Usage" means the use of cellular airtime services for any
                  purpose.

         1.8.     "Cutover Date" means the date on which GTEW ceases to provide
                  Services for HighwayMaster and SBMS begins to provide the
                  Services to HighwayMaster.

         1.9.     "Data CTS" means the use of cellular airtime services for the
                  purpose of transmitting data communications via cellular
                  networks.

         1.10.    "End-Users" means the customers of HighwayMaster who purchase
                  the enhanced services for use in connection with the Units.

         1.11.    "FCC" means the Federal Communications Commission.

         1.12.    "HighwayMaster Information" means the technical and business
                  information which is proprietary and confidential to
                  HighwayMaster, and such other information marked
                  "Confidential" and disclosed to SBMS by HighwayMaster pursuant
                  to this Agreement. The HighwayMaster Information shall not
                  include information which: (a) is now or in the future becomes
                  generally known to the public through no fault of SBMS; (b)
                  prior to disclosure hereunder, is properly within the
                  legitimate possession of SBMS, without any restriction on
                  disclosure; (c) subsequent to disclosure hereunder, the
                  information is lawfully received from a third party having
                  rights to disseminate the information and without any
                  restriction on disclosure; (d) is obligated to be produced
                  under order of a court of competent jurisdiction or by means
                  of other valid legal process; provided, however, that SBMS
                  shall notify HighwayMaster of such order or process so that
                  HighwayMaster may seek a protective order; and/or (e) was
                  independently developed by SBMS without reference to or
                  reliance on the HighwayMaster Information.

         1.13.    "IRSA" means an Intercarrier Roamer Service Agreement.

         1.14.    "IRSA Addendum" means an Addendum to an Intercarrier Roamer
                  Service Agreement between SBMS and a Carrier to facilitate the
                  provision of domestic


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                  celluar roaming service to HighwayMaster's end users in that
                  Carrier's market(s).

         1.15.    "Market" means a cellular service area operated by a Carrier,
                  which consists of one or more licensed areas defined by the
                  Federal Communications Commission as either metropolitan
                  statistical areas ("MSAs") or rural service areas ("RSAs").

         1.16.    "Material Default" means any material breach of any
                  obligation, representation, warranty or covenant by a party to
                  this Agreement which has not been cured within thirty (30)
                  days after notice of such breach is given to the breaching
                  party by the non-breaching party.

         1.17.    "Non-SBMS Carrier" means a Carrier with which SBMS has signed
                  an IRSA that is not an SBMS Affiliate.

         1.18.    "Non-SBMS Market" means any domestic cellular market, whether
                  an MSA or RSA or a combination thereof, for which a Non-SBMS
                  Carrier holds the FCC license or in which a Non-SBMS Affiliate
                  manages or holds a controlling interest.

         1.19.    "NPA/NXX" means a ten thousand block of telephone numbers
                  represented by the NPA (numbering plan area or area code) and
                  NXX (prefix) assigned to that block of numbers.

         1.20.    "NSC" means the Network Services Center owned and operated by
                  HighwayMaster.

         1.21.    "Roaming Rate" means the agreed upon rate established by
                  HighwayMaster and each Carrier in a Market operated by such
                  Carrier for CTS Usage in that Carrier's Market.

         1.22.    "SBMS Carrier" means a Carrier that is SBMS or an SBMS
                  Affiliate.

         1.23.    "SBMS Information" means the technical and business
                  information which is proprietary and confidential to SBMS, and
                  such other information marked "Confidential" and disclosed to
                  HighwayMaster by SBMS pursuant to this Agreement. The SBMS
                  Information shall not include information which: (a) is now or
                  in the future becomes generally known to the public through no
                  fault of HighwayMaster; (b) prior to disclosure hereunder, is
                  properly within the legitimate possession of HighwayMaster,
                  without any restriction on disclosure; (c) subsequent to
                  disclosure hereunder, the information is lawfully received
                  from a third party having rights to disseminate the
                  information and without any restriction on disclosure; (d) is
                  obligated to be produced under order of a court of competent
                  jurisdiction or by means of other valid legal process;
                  provided, however, that HighwayMaster shall notify SBMS of
                  such order or process so SBMS may seek a protective order;
                  and/or (e) was independently developed by the HighwayMaster
                  without reference to or reliance on SBMS Information.


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         1.24.    "SBMS Market" means any domestic cellular market, whether an
                  MSA or an RSA or a combination thereof, for which SBMS or an
                  SBMS Affiliate holds the FCC license or in which SBMS or an
                  SBMS Affiliate manages or holds a controlling interest.
                  Attached hereto as Exhibit "A" is a list of all current SBMS
                  Markets.

         1.25.    "Services" means the administrative and settlement services to
                  be provided by SBMS to HighwayMaster for HighwayMaster's use
                  in connection with its provision of enhanced services to its
                  End-Users.

         1.26.    "SID" means the five (5) digit system identification code
                  assigned to a Market.

         1.27.    "Unit" means the HighwayMaster mobile communications unit.

         1.28.    "Voice CTS" means the use of cellular airtime services for the
                  purpose of transmitting voice communications via cellular
                  networks.


                              II. SBMS' OBLIGATIONS

2.       SBMS' Obligations. In addition to the other covenants, terms and
         conditions set forth in this Agreement, effective as of the Cutover
         Date SBMS agrees to provide the following Services for HighwayMaster's
         use in providing enhanced services to its End-Users in connection with
         their use of the Units in any Covered Markets.

         2.1.     BID. SBMS will maintain the HighwayMaster BID for NPA/NXXs
                  solely for the use of HighwayMaster as permitted by any laws,
                  rules or regulations. The BIDs will permit identification of
                  Units in each Market as permitted by any laws, rules or
                  regulations.

         2.2.     Operational Services.

                  2.2.1.   Visibility. SBMS will provide HighwayMaster with
                           access to Visibility services for the HighwayMaster
                           BID, subject to its ability to obtain GTE-TSI's
                           consent to do so.

                  2.2.2.   SBMS will provide, or cause to be provided, to
                           HighwayMaster CIBER in collect tapes reflecting CTS
                           Usage associated with the HighwayMaster BID, subject
                           to its ability to obtain GTE-TSI's consent to do so.
                           Whether SBMS provides the tapes or causes them to be
                           provided directly to HighwayMaster by GTE-TSI shall
                           be decided in SBMS's sole discretion, as it deems
                           appropriate or feasible from time to time.

                  2.2.3.   Within thirty (30) days of the end of each settlement
                           cycle, SBMS will provide HighwayMaster with a
                           financial summary consisting of charges by


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                           SBMS Carriers and Non-SBMS Carriers for CTS Usage
                           associated with the HighwayMaster BID in each
                           Carrier's respective Markets during that settlement
                           cycle, subject to its ability to obtain GTE-TSI's
                           consent to do so. SBMS will also provide CHARM
                           Reports to back up the summary, also subject to
                           GTE-TSI's consent.

                           2.2.3.1. As an alternative to the procedure set forth
                                    in the preceding subsection, SBMS in its
                                    sole discretion from time to time, may, with
                                    GTE-TSI's consent, cause GTE-TSI to provide
                                    HighwayMaster with access to the summary
                                    financial information described above
                                    through GTE-TSI's ACCESSibility service.

                  2.2.4.   Following the close of each settlement cycle, SBMS
                           shall provide HighwayMaster with an invoice for the
                           Carrier Charges based upon the net settlement amounts
                           funded by SBMS with respect to the HighwayMaster BID.

         2.3.     Payment of Charges.

                  2.3.1.   Net Settlement. SBMS shall act as HighwayMaster?s
                           payment agent for purposes of timely paying any and
                           all net settlement amounts charged by Carriers with
                           respect to NPA/NXXs and/or BID(s) assigned to
                           HighwayMaster or its End-Users in the Carrier?s
                           Market ("Carrier Charges"). The parties acknowledge
                           and understand that SBMS is merely acting as the
                           payment agent of HighwayMaster in connection with the
                           CIBERNET net settlement process and that
                           HighwayMaster is solely liable for any and all
                           amounts due Carriers for CTS Usage with respect to
                           the HighwayMaster BID.

                  2.3.2.   Reimbursement. HighwayMaster shall reimburse SBMS for
                           any and all amounts paid by SBMS to Carriers for
                           Carrier Charges, regardless of whether such charges
                           were improperly invoiced or not. SBMS shall not have
                           any responsibility to investigate or determine
                           whether the Carrier Charges are correct, and
                           HighwayMaster has no defense to claims by SBMS for
                           amounts paid by it for Carrier Charges based upon the
                           impropriety of the Carrier Charges.

                  2.3.3.   Improper Billing by Carriers. From time to time,
                           various carriers incorrectly rate or charge for CTS
                           Usage for cellular service provided to End-Users in
                           their Market. The parties anticipate that most
                           Carriers will sign the IRSA Addendum in the form of
                           that attached hereto as Exhibit 1. In those cases,
                           HighwayMaster will bear all responsibility for
                           seeking refunds for overcharges from the Carriers and
                           for making payments to Carriers for undercharges, and
                           will do so outside of the CIBERNET settlement
                           process. With respect to any Carrier(s) that are
                           unwilling to sign the Exhibit 1 form of IRSA Addendum
                           solely because of the paragraph 3 adjustment language


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                           therein, SBMS agrees to modify that language, and
                           SBMS and HighwayMaster agree to cooperate in
                           implementing a mutually acceptable mechanism for SBMS
                           to facilitate refunds from those Carriers for
                           improperly rated or charged CTS Usage.

                  2.3.4.   HighwayMaster agrees to indemnify and hold harmless
                           SBMS from any and all claims, losses, damages, causes
                           of action, costs (including reasonable attorney's
                           fees) or reasonable expenses incurred by SBMS as a
                           result of any claim or action brought by a third
                           party and arising from the payment of amounts to
                           Carriers under this Agreement.

                  2.3.5.   Alternative Billing Arrangements. Nothing herein
                           restricts HighwayMaster from entering into separate
                           agreements with Non-SBMS Carriers to establish
                           alternate standards, processes and arrangements by
                           which HighwayMaster would settle and be billed for
                           the use of such Non-SBMS Carrier's CTS ("Alternative
                           Billing Arrangements"), provided, that HighwayMaster
                           shall not be relieved of any of its obligations
                           hereunder. SBMS shall have no obligation to provide
                           any Services or assistance to HighwayMaster in
                           connection with the Alternative Billing Arrangement.

         2.4.     Provision of CTS.

                  2.4.1.   SBMS Markets. HighwayMaster hereby authorizes SBMS
                           and SBMS agrees that it will negotiate and execute
                           IRSA Addenda and cause HighwayMaster to be provided
                           with CTS in the SBMS Markets under the same terms
                           (other than rates) that it negotiates such CTS access
                           in Non-SBMS Markets. To the extent that an SBMS
                           Market loses the required FCC license or other
                           necessary approvals, such SBMS Market shall have no
                           obligation to provide CTS to HighwayMaster.

                  2.4.2.   Non-SBMS Markets. HighwayMaster hereby authorizes
                           SBMS and SBMS agrees that it will use commercially
                           reasonable efforts to negotiate and execute IRSA
                           Addenda in substantially the form of that attached
                           hereto as Exhibit 1 to cause HighwayMaster to be
                           provided with CTS in the Non-SBMS Markets. SBMS shall
                           ensure that its IRSA Addenda with the Non-SBMS
                           Carriers permit for rating of End-User CTS at the
                           rates set forth in HighwayMaster's CSAs with the
                           Non-SBMS Carriers. SBMS will have no liability to
                           HighwayMaster or any third party for its failure to
                           obtain IRSA Addenda from any particular Carriers or
                           from any particular number of Carriers either before
                           or after the Cutover Date. The terms and conditions
                           of all IRSA Addenda are confidential and proprietary
                           to SBMS and are subject to the provisions of this
                           Agreement relating to SBMS Information.


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                           III. SBMS' REPRESENTATIONS

3.       SBMS' Representations.

         3.1.     Other Material Agreements. The execution, delivery and
                  performance of this Agreement does not conflict with or result
                  in a material breach of any provision of any material
                  agreement to which SBMS is a party.

         3.2.     Valid Execution. This Agreement has been duly executed and
                  delivered by an authorized representative of SBMS and
                  constitutes a valid and legally binding obligation of SBMS,
                  enforceable against it in accordance with its terms.

                       IV. HIGHWAYMASTER'S REPRESENTATIONS

4.       HighwayMaster's Representations.

         4.1.     Other Material Agreements. The execution, delivery and
                  performance of this Agreement does not conflict with or result
                  in a material breach of any provision of any material
                  agreement to which HighwayMaster is a party.

         4.2.     Valid Execution. This Agreement has been duly executed and
                  delivered by an authorized representative of HighwayMaster and
                  constitutes a valid and legally binding obligation of
                  HighwayMaster, enforceable against it in accordance with its
                  terms.

                         V. HIGHWAYMASTER'S OBLIGATIONS

5.       HighwayMaster's Obligations.

         5.1.     NPA/NXXs. HighwayMaster will provide to SBMS the NPA/NXX
                  combinations for its existing End-Users and all BIDs for those
                  NPA/NXXs. HighwayMaster's NPA/NXX combinations are currently
                  associated with a BID assigned to GTEW. HighwayMaster will
                  cause GTEW to cooperate with SBMS in assigning to SBMS the
                  NPA/NXXs and the BID with which they are associated.
                  HighwayMaster will ensure that the NPA/NXXs shall be in a
                  designated numbering system compatible with GTE
                  Telecommunications Systems Incorporated ("GTE-TSI") for
                  purposes of validation. The NPA/NXXs shall be stored and
                  maintained in a validation database at GTE-TSI (the
                  "HighwayMaster Database"). HighwayMaster and SBMS shall have
                  access to the HighwayMaster Database at all times during the
                  term of this Agreement and for a reasonable time period after
                  expiration or termination of this Agreement to allow each
                  party to perform or complete any outstanding billing or other
                  functions under this Agreement. [Text has been omitted
                  pursuant to a request for confidential treatment. The omitted
                  material has been filed separately with the SEC.]


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         5.2.     Negotiation of CTS Rates with Carriers. HighwayMaster is
                  solely responsible for the negotiation of any rates for CTS,
                  whether Voice CTS or Data CTS, and the execution of any CSAs
                  in Covered Markets. HighwayMaster will not sign any CSAs that
                  refer to SBMS or an administrative carrier without SBMS' prior
                  consent, nor will it sign any CSAs that conflict with the
                  terms of this Agreement. In order to permit SBMS to provide
                  the Services hereunder, HighwayMaster is required to notify
                  SBMS of the effective dates of, and supply SBMS with fully
                  executed copies of, any CSAs with Non-SBMS Markets.
                  HighwayMaster is also required to promptly notify SBMS of the
                  termination or expiration of any CSA. The terms and conditions
                  contained in these CSAs are confidential and proprietary to
                  HighwayMaster and are subject to the provisions of this
                  Agreement relating to HighwayMaster Information.

         5.3.     CTS Rates and Roaming Rates Acknowledgments. HighwayMaster
                  will be solely responsible for the negotiation and
                  establishment of CTS rates or other pricing with Non-SBMS
                  Carriers through its CSAs with the Non-SBMS Carriers.
                  HighwayMaster acknowledges that SBMS is not authorized and
                  cannot establish Roaming Rates for any Non-SBMS Market.
                  HighwayMaster acknowledges and agrees that it shall pay SBMS
                  an amount, including, but not limited to, the full amount of
                  all charges assessed by each Carrier with respect to
                  HighwayMaster NPA/NXXs and/or BIDs and paid by SBMS through
                  net settlement or otherwise. Nothing herein shall be construed
                  as requiring SBMS to offset any difference between the actual
                  rates charged by a Carrier in a particular Market and the
                  Roaming Rates or other rates requested or negotiated by
                  HighwayMaster with that Carrier. HighwayMaster further
                  acknowledges that IRSA Addenda between SBMS and the Non-SBMS
                  Carriers are subject to termination. To the extent any of the
                  IRSA Addenda are terminated, SBMS is not obligated to make
                  available Services in the Markets governed by such terminated
                  IRSA Addendum and SBMS shall have no obligation to
                  HighwayMaster for any damages, losses, or other effects of
                  such termination. SBMS will use commercially reasonable
                  efforts to maintain the IRSA Addenda with Non-SBMS Carriers.

         5.4.     Activations/Identification Changes. HighwayMaster shall be
                  responsible for all activations and identification changes
                  with respect to End-Users.

         5.5.     Technical Support. HighwayMaster shall be responsible for
                  responding to all End-User trouble tickets and will resolve
                  technical issues with Carriers and GTE-TSI.

         5.6.     Carrier Contacts. HighwayMaster will remain the point of
                  contact for Carriers with respect to rates, contract issues or
                  program changes. HighwayMaster shall handle all switch
                  configuration and network issues directly with each Carrier.

         5.7.     Regulatory and Legal Approvals. To the extent HighwayMaster is
                  required to obtain any federal, state, local or regulatory
                  approvals, licenses or certifications to provide enhanced
                  services to its End-Users, HighwayMaster is solely responsible
                  for 


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                  obtaining such approvals, licenses or certifications.
                  HighwayMaster agrees to indemnify and hold harmless SBMS from
                  any claims, losses, damages, causes of action, costs
                  (including reasonable attorney's fees) or reasonable expenses
                  incurred by SBMS as a result of any claim or action brought by
                  a third party and arising from HighwayMaster's failure to
                  obtain any required licenses, approvals or other
                  certifications.

         5.8.     Technical Data Updates. SBMS and HighwayMaster will issue a
                  joint technical update to the Carriers explaining the
                  transition from HighwayMaster's prior administrative carrier
                  to SBMS. HighwayMaster shall compose and provide additional
                  technical data updates to all carriers at least two (2) times
                  per year, provided that HighwayMaster shall not release any
                  updates without prior written approval from SBMS, which
                  approval shall not be unreasonably withheld.

         5.9.     Technical Data Sheets. HighwayMaster will request and maintain
                  technical data sheets from Carriers for trouble resolution and
                  record maintenance.

         5.10.    CTS Restrictions. HighwayMaster, and not SBMS, shall be
                  responsible for informing Carriers of any required call
                  restrictions with respect to the HighwayMaster NPA/NXXs or
                  Units, [Text has been omitted pursuant to a request for
                  confidential treatment. The omitted material has been filed
                  separately with the SEC.] HighwayMaster acknowledges and
                  agrees that HighwayMaster will be solely responsible for any
                  amounts owed for CTS Usage or any other costs incurred in
                  Non-SBMS Markets where the Carrier does not provide or install
                  the required restrictions. HighwayMaster shall ensure that its
                  CSAs with Carriers impose obligations on the Carriers to
                  implement the dialing restrictions. HighwayMaster agrees to
                  maintain its current security and fraud prevention systems and
                  validation procedures in place and active, and to the extent
                  HighwayMaster ceases any such security protections,
                  HighwayMaster will be liable for fraudulent End-User CTS.
                  End-Users shall be permitted to dial 911 emergency services,
                  but HighwayMaster acknowledges that neither SBMS nor the SBMS
                  Markets provide or control the provision of 911 emergency
                  services in any Market.

                            VI. INTELLECTUAL PROPERTY

6.       Intellectual Property.

         6.1.     No Assignment or License of Intellectual Property. Nothing
                  contained herein shall be construed to grant SBMS any right,
                  title or license in or to, whether express or implied, the
                  patents, copyrights, trademarks, trade secrets, mask works or
                  other proprietary rights of HighwayMaster or any improvements
                  and/or modifications thereto. Nothing contained herein shall
                  be construed to grant HighwayMaster any right, title or
                  license in or to, whether express or implied, the patents,
                  copyrights, trademarks, trade secrets, mask works or other
                  proprietary rights of SBMS or any improvements and/or
                  modifications thereto.

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         6.2.     Intellectual Property Indemnity. HighwayMaster agrees to
                  indemnify and hold SBMS harmless from and against any loss,
                  liability, damage or expense (including attorneys' fees and
                  court costs) that may result by reason of any infringement or
                  claim of infringement, of any entity's intellectual property
                  rights or other proprietary interest, arising out of any
                  services provided by HighwayMaster to End Users or Carriers.
                  This indemnity shall include, but is not limited to, any
                  claims by GTEW or its affiliates with respect to any
                  intellectual property employed by HighwayMaster. SBMS shall
                  promptly notify HighwayMaster of any claim for which it is
                  responsible hereunder.

                              VII. CONFIDENTIALITY

7.       Confidentiality.

         7.1.     Ownership, Use and Confidentiality of HighwayMaster
                  Information. HighwayMaster Information shall remain the
                  property of HighwayMaster and its End-Users. SBMS may only use
                  the HighwayMaster Information to the extent set forth herein
                  or as required to perform the Services hereunder, unless SBMS
                  obtains the prior written consent of HighwayMaster to use the
                  HighwayMaster Information for another purpose. SBMS shall not
                  disclose the HighwayMaster Information to any third party
                  without the prior written consent of HighwayMaster. If SBMS
                  receives or is served with any order, subpoena, demand or
                  other request from a governmental agency, court, or other
                  legal forum to produce the HighwayMaster Information, in whole
                  or in part, SBMS will provide HighwayMaster with prompt notice
                  of such request so that HighwayMaster at its expense, may seek
                  a protective order or such other remedy to prevent production
                  of the HighwayMaster Information. If SBMS ultimately complies
                  with a proper request, SBMS will not be in violation of this
                  Section. Upon the termination or expiration of this Agreement
                  or, with respect to any HighwayMaster Information, on such
                  earlier date that SBMS in its opinion, shall no longer require
                  the HighwayMaster Information to provides the Services
                  hereunder, SBMS shall, at HighwayMaster's request, either
                  erase the HighwayMaster Information from any files maintained
                  by SBMS or return the HighwayMaster Information to
                  HighwayMaster. SBMS agrees to protect and safeguard the
                  confidentiality of the HighwayMaster Information to the same
                  degree and extent as SBMS protects and safeguards its own
                  confidential and proprietary information.

         7.2.     Ownership, Use and Confidentiality of SBMS Information. SBMS
                  Information shall remain the property of SBMS. HighwayMaster
                  may only use the SBMS Information to the extent set forth
                  herein or as required to perform its obligations hereunder,
                  unless HighwayMaster obtains the prior written consent of SBMS
                  to use the SBMS Information for another purpose. HighwayMaster
                  shall not disclose the SBMS Information to any third party
                  without the prior written consent of SBMS. If HighwayMaster
                  receives or is served with any order, subpoena, demand or
                  other 

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                  request from a governmental agency, court, or other legal
                  forum to produce the SBMS Information, in whole or in part,
                  HighwayMaster will provide SBMS with prompt notice of such
                  request so that SBMS at its expense, may seek a protective
                  order or such other remedy to prevent production of the SBMS
                  Information. If HighwayMaster ultimately complies with a
                  proper request, HighwayMaster will not be in violation of this
                  Section. Upon the termination or expiration of this Agreement
                  or, with respect to any SBMS Information, on such earlier date
                  that HighwayMaster in its opinion, shall no longer require the
                  SBMS Information to perform its obligations hereunder,
                  HighwayMaster shall, at SBMS' request, either erase the SBMS
                  Information from any files maintained by HighwayMaster or
                  return the SBMS Information to SBMS. HighwayMaster agrees to
                  protect and safeguard the confidentiality of the SBMS
                  Information to the same degree and extent as HighwayMaster
                  protects and safeguards its own confidential and proprietary
                  information.

                             VIII. FEES AND INTEREST

8.       Fees and Interest.

         8.1.     Monthly Administrative Carrier Fee. In exchange for the
                  Services provided hereunder to HighwayMaster by SBMS,
                  HighwayMaster shall pay to SBMS a monthly recurring
                  Administrative Carrier Fee within thirty (30) days of receipt
                  of an invoice for the same. Prior to the Cutover Date, the
                  Administrative Carrier Fee will be [Text has been omitted
                  pursuant to a request for confidential treatment. The omitted
                  material has been filed separately with the SEC.] per month.
                  After the Cutover Date the Administrative Carrier Fee will be
                  [Text has been omitted pursuant to a request for confidential
                  treatment. The omitted material has been filed separately with
                  the SEC.] per month.

         8.2.     Carrier Charge Reimbursement. HighwayMaster shall pay SBMS for
                  any and all Carrier Charges (including all SBMS and Non-SBMS
                  CTS and Roaming Charges) amounts paid by SBMS as set forth
                  elsewhere in this Agreement.

         8.3.     Clearinghouse Fees. [Text has been omitted pursuant to a
                  request for confidential treatment. The omitted material has
                  been filed separately with the SEC.]

         8.4.     Late Payment. Any Administrative Carrier Fees, Carrier Charge
                  reimbursements or other charges or reimbursements not paid by
                  the due date shall accrue interest on the unpaid amount until
                  paid at the rate of 1 1/2 % per month or the maximum amount
                  allowed by law, whichever is less.

                            IX. TERM AND TERMINATION

9.       Term and Termination.



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         9.1.     Initial Term. The initial term of this Agreement shall be for
                  a period of three years commencing on the date of execution of
                  this Agreement by both parties and ending on the third
                  anniversary of such date (the "Initial Term").

         9.2.     Renewal Term. Upon expiration of the Initial Term, this
                  Agreement shall automatically renew upon the same terms and
                  conditions for five (5) consecutive one (1) year renewal terms
                  (a "Renewal Term"), unless either party gives the other
                  written notice of its intent not to renew at least six (6)
                  months prior to the expiration of the existing Renewal Term.

         9.3.     Termination for Cause. In the event of a Material Default by
                  either party under this Agreement, the non-defaulting party
                  may terminate this Agreement by giving notice of such
                  termination to the other party to this Agreement, which notice
                  of termination shall specify a date no earlier than sixty (60)
                  days after the date such notice is given for such termination.

         9.4.     Termination for Nonpayment. In the event that HighwayMaster
                  fails to pay SBMS any amounts owed under this Agreement within
                  thirty (30) days of actual receipt of an Invoice and
                  HighwayMaster fails to fully cure such payment default within
                  ninety (90) days after notice by SBMS of such payment default,
                  then SBMS may terminate this Agreement by giving notice of
                  such termination to HighwayMaster, which notice of termination
                  shall specify a date no earlier than the date such notice is
                  given for such termination.

         9.5.     Termination for Insolvency. If HighwayMaster makes an
                  assignment for the benefit of creditors or files a voluntary
                  petition under Title 11 of the United States Code or under any
                  similar state insolvency laws or if HighwayMaster shall have
                  an involuntary petition for bankruptcy filed against it under
                  Title 11 of the United States Code and such involuntary
                  petition is not dismissed within thirty (30) days; or a
                  trustee or receiver is appointed to administer HighwayMaster's
                  business or assets, SBMS shall have the right to terminate
                  this Agreement effective upon notification of such termination
                  to HighwayMaster.

         9.6.     Termination for Impossibility. SBMS may terminate this
                  Agreement immediately upon written notice to HighwayMaster at
                  any time more than forty-five (45) days after the scheduled
                  Cutover Date if at such time HighwayMaster has not yet
                  effected the transfer of the HighwayMaster BID and associated
                  NPA/NXXs to SBMS.

         9.7.     Transition Period. Upon expiration of the Initial Term or any
                  Renewal Term or the termination of this Agreement under
                  Sections 9.2 or 9.3 (except when SBMS terminates HighwayMaster
                  as a result of a Material Default), SBMS shall continue to
                  provide the Services to HighwayMaster in accordance with the
                  terms and conditions of this Agreement for a period not to
                  exceed nine (9) months to permit 


ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 12


   13

                  HighwayMaster to transition from SBMS to another party (the
                  "Transition Period"). At any time during the Transition
                  Period, HighwayMaster may terminate the provision of Service
                  by SBMS upon thirty (30) days written notice. Upon the
                  expiration of the Transition Period, SBMS shall have no
                  obligation to provide the Services to HighwayMaster under any
                  circumstances.

                    X. TRANSITION OF ADMINISTRATIVE CARRIERS

10.      The Parties agree to the following provisions in connection with
         HighwayMaster's transition of administrative carriers from GTEW to
         SBMS:

         10.1.    The Cutover Date will be September 30, 1999, unless an earlier
                  date is agreed to in writing by the parties hereto.

         10.2.    HighwayMaster will cause GTEW to cooperate with SBMS in
                  assigning to SBMS the NPA/NXXs and the BID with which they are
                  associated effective as of the Cutover Date. HighwayMaster
                  will cause any existing GTEW roaming addenda that address
                  HighwayMaster service to terminate on or before the Cutover
                  Date. HighwayMaster will cause any existing Cellular Service
                  Agreements that reference GTEW as its administrative carrier
                  or that SBMS has not approved to terminate on or before the
                  Cutover Date.

         10.3.    HighwayMaster will use commercially reasonable efforts to sign
                  Cellular Service Agreements with as many of SBMS' domestic
                  cellular roaming partners as possible to be effective as of
                  the Cutover Date. HighwayMaster will continue its efforts to
                  sign up Carriers after the Cutover Date.

         10.4.    SBMS will use commercially reasonable efforts to sign IRSA
                  Addenda substantially in the form of that attached as Exhibit
                  1 hereto with as many of its domestic cellular roaming
                  partners as possible to be effective as of the Cutover Date.
                  SBMS will continue its efforts to sign up Carriers after the
                  Cutover Date in accordance with Section 2.4 above.

         10.5.    SBMS and HighwayMaster will coordinate their respective
                  efforts to obtain IRSA Addenda and Cellular Service Agreements
                  from the same Carriers.

                                XI. MISCELLANEOUS

11.      Miscellaneous.

         11.1.    Force Majeure. Each party hereto shall be excused from
                  performance hereunder for any period and to the extent that it
                  is prevented from performing any action pursuant hereto, in
                  whole or in part, as a result of delays beyond its control
                  caused by the other party or by an act of God or the public
                  enemy, fire, floods, epidemics, quarantine 


ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 13


   14

                  restrictions, civil disturbance, court order, labor dispute,
                  third party nonperformance (except to the extent such third
                  party nonperformance is wrongfully caused by a party to this
                  Agreement), or other cause beyond its control, including
                  without limitation failures or fluctuations in electrical
                  power, heat, light or air conditioning.

         11.2.    Single Point of Contact. SBMS and HighwayMaster shall each
                  identify in writing, subject to change at any time, a single
                  point of contact to coordinate activations, identify existing
                  problems with the provision of the Services by SBMS. Each
                  party will provide a contact person with adequate technical
                  knowledge and understanding of the mutual obligations
                  hereunder and such contact person will be available on a
                  regular basis Monday through Friday from 8:00 a.m. to 5:00
                  p.m. Central Standard Time.

         11.3.    Severability. Any provision of this Agreement which is
                  prohibited, unenforceable or is declared or found to be
                  illegal, unenforceable or void, in any jurisdiction shall, as
                  to such jurisdiction, be ineffective only to the extent of
                  such prohibition or unenforceability without invalidating the
                  remainder of such provision or the remaining provisions of
                  this Agreement or affecting the validity or enforceability of
                  such provision in any other jurisdiction.

         11.4.    Nondisclosure/Media Releases. All media releases, public
                  announcements and public disclosures by any party hereto
                  relating to this Agreement or its subject matter, including
                  without limitation promotional or marketing material, but not
                  including any announcement intended solely for internal
                  distribution or any disclosure required by legal, accounting
                  or regulatory requirements beyond the reasonable control of
                  such party, shall be coordinated with and approved by the
                  other party hereto prior to the release thereof, which
                  approval shall not be unreasonably withheld or delayed. The
                  terms of this Agreement are confidential except that either
                  party may disclose the terms of this Agreement to any of its
                  employees, consultants or professionals on a "need to know
                  basis" to permit performance hereunder. Neither party shall
                  announce or disclose to any third party, the terms and
                  conditions contained herein or any discussions relating
                  thereto, without the prior written consent of the other party,
                  except as required by law, in which case the party required to
                  make disclosure shall give the other party prompt notice of
                  any such requirement so that the other party can take any
                  actions it deems appropriate to protect the information from
                  disclosure. Notwithstanding the above, HighwayMaster shall be
                  permitted to disclose this Agreement to the Securities and
                  Exchange Commission ("SEC") and file it therewith, as
                  required. HighwayMaster shall provide the SEC with a clean and
                  redacted copy of the Agreement to indicate to the SEC which
                  Sections should be redacted and unavailable for public review.
                  A copy of the Agreement with the proposed redactions will be
                  provided to SBMS twenty (20) business days prior to filing the
                  Agreement with the SEC, and SBMS shall have such twenty (20)
                  business days to request additional or different redactions.
                  In the event no such comments are provided to HighwayMaster by
                  SBMS in such time period, HighwayMaster shall be authorized to

ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 14



   15

                  file this Agreement with the SEC in the form given to SBMS for
                  review. To the extent the SEC or HighwayMaster determines that
                  any requested redactions are not allowed by the SEC,
                  HighwayMaster must notify SBMS of the specific changes
                  required by the SEC prior to filing this Agreement with the
                  SEC.

         11.5.    Notices. Any notice required by this Agreement must be given
                  by depositing a copy of such notice (i) in the United States
                  mail, postage prepaid, certified return receipt requested or
                  (ii) in overnight delivery or (ii) via facsimile. Any such
                  notice will be deemed to be received upon the earlier of
                  verification of delivery or on the third day after depositing
                  a copy of such notice in the mail or overnight delivery,
                  except that notices received by facsimile shall only be deemed
                  effective upon actual receipt by the individual with the title
                  set forth below as confirmed solely by such individual. Any
                  such notice will be given at the following addresses or to
                  such later addresses of which the sending party has received
                  actual or constructive notice:

                      If to HighwayMaster:
                      HighwayMaster Corporation
                      1155 Kas Drive
                      Richardson, Texas 75081
                      Attention: General Counsel
                      FAX No.: (972) 301-2263

                      If to SBMS:
                      Southwestern Bell Mobile Systems, Inc.
                      17330 Preston Road, Suite 100A
                      Dallas, Texas 75252
                      Attention: Director, Intercarrier Services
                      FAX No.: 972-733-6155

                      With a copy to:
                      Southwestern Bell Mobile Systems, Inc.
                      17330 Preston Road, Suite 100A
                      Dallas, Texas 75252
                      Attention:  Vice President, Secretary, and General Counsel
                      FAX No.: 972-733-2021

         11.6.    Legal Representation. HighwayMaster acknowledges that SBMS has
                  offered no legal advice or counsel to HighwayMaster nor made
                  any representations to HighwayMaster regarding HighwayMaster's
                  exemption from the jurisdiction of federal, state, or local
                  governmental agencies with potential jurisdiction over the
                  parties herein and the Services to be rendered hereunder and
                  SBMS has not offered HighwayMaster any legal advice or counsel
                  regarding the subject matter of this Agreement. SBMS
                  acknowledges that HighwayMaster has offered no legal advice or
                  counsel to SBMS nor made any representations to SBMS regarding
                  SBMS' exemption from the 


ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 15


   16

                  jurisdiction of federal, state, or local governmental agencies
                  with potential jurisdiction over the parties herein and the
                  Services and obligations to be rendered hereunder and
                  HighwayMaster has not offered SBMS any legal advice or counsel
                  regarding the subject matter of this Agreement.

         11.7.    Interpretation. Headings used in this Agreement are for
                  convenience only and will not be deemed to be operative text.
                  Terms of gender will be deemed interchangeable, as will
                  singular and plural terms, in each case unless the context
                  otherwise requires.

         11.8.    Execution. This Agreement shall be deemed to be executed at
                  such time as all parties hereto have signed a counterpart
                  hereof and each party hereto has received from each of the
                  other parties hereto an originally-signed counterpart or a
                  facsimile transmission or other replication of an
                  originally-signed counterpart.

         11.9.    Waiver. The failure of either party to enforce, in any one or
                  more instances, performance of any of the terms, covenants or
                  conditions of this Agreement shall not be construed as a
                  waiver or a relinquishment of any right or claim granted or
                  arising hereunder or of the future performance of any such
                  term, covenant, or condition, and such failure shall in no way
                  affect the validity of this Agreement or the rights and
                  obligations of the parties hereto. The parties acknowledge
                  that a waiver of any term or provision hereof may only be
                  given by a written instrument executed by the party granting
                  the waiver.

         11.10.   WARRANTY DISCLAIMER. SBMS' AND HIGHWAYMASTER'S OBLIGATIONS
                  HEREUNDER ARE IN LIEU OF ALL WARRANTIES, EXPRESS OR IMPLIED.
                  SBMS MAKES NO WARRANTIES, EXPRESS OR IMPLIED REGARDING ANY
                  GOODS, SERVICES OR EQUIPMENT TO BE PROVIDED HEREIN, OR AS TO
                  ANY CTS TO BE PROVIDED IN ANY SBMS MARKETS INCLUDING ANY
                  WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
                  PURPOSE.

         11.11.   NO LIABILITY FOR INDIRECT DAMAGES. SBMS SHALL NOT BE LIABLE TO
                  HIGHWAYMASTER OR ANY THIRD PARTY, AND HIGHWAYMASTER SHALL NOT
                  BE LIABLE TO SBMS OR ANY THIRD PARTY, FOR INDIRECT,
                  INCIDENTAL, CONSEQUENTIAL, RELIANCE, OR SPECIAL DAMAGES,
                  INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOST PROFITS,
                  REGARDLESS OF THE FORM OF ACTION, WHETHER IN CONTRACT,
                  INDEMNITY, WARRANTY, STRICT LIABILITY OR TORT, ARISING FROM OR
                  RELATED TO THEIR PERFORMANCE OR NON-PERFORMANCE HEREUNDER.

         11.12.   LIMITATION OF LIABILITY. THE LIABILITY OF EITHER PARTY FOR ANY
                  CLAIM ASSERTED BY THE OTHER PARTY OR ANY THIRD PARTY ARISING
                  OUT OF THIS AGREEMENT (OTHER THAN CLAIMS BY SBMS FOR



ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 16


   17

                  REIMBURSEMENT OF CARRIER CHARGES OR INTELLECTUAL PROPERTY
                  INDEMNITY IN ACCORDANCE WITH THE TERMS OF THIS AGREEMENT)
                  SHALL BE LIMITED TO AN AMOUNT EQUAL TO THE TOTAL AMOUNTS
                  INVOICED TO HIGHWAYMASTER IN THE TWELVE (12) MONTH PERIOD
                  IMMEDIATELY PRECEDING THE EVENT GIVING RISE TO THE CLAIM.

         11.13.   Counterparts. This Agreement may be executed in any number of
                  counterparts, each of which shall be deemed to be an original,
                  and all of which together shall constitute one and the same
                  instrument notwithstanding that all parties are not
                  signatories to each counterpart.

         11.14.   Assignability and Binding Effect. This Agreement shall inure
                  to the benefit of and be binding upon the parties hereto and
                  their respective successors and permitted assigns. No party
                  may assign this Agreement without the prior written consent of
                  the other party hereto; provided, however, that SBMS may
                  assign this Agreement, and its rights and obligations
                  hereunder, to any of its Affiliates without the consent of any
                  other party.

         11.15.   Amendments. This Agreement may not be modified, amended or
                  supplemented except by an agreement in writing signed by all
                  of the parties hereto. Neither party shall accept or act upon
                  any instructions, directions, and/or modifications concerning
                  that party's performance hereunder which would affect the
                  terms, conditions, and/or pricing of this Agreement unless
                  authorized by the other party.

         11.16.   Expenses, Taxes, Etc. Each of the parties hereto shall pay all
                  fees and expenses incurred by it in connection with the
                  preparation and negotiation of this Agreement. There shall be
                  added to any charges incurred and payable by HighwayMaster
                  under this Agreement, an amount equal to any tariff, duty, or
                  levy tax including but not limited to sales, ad valorem and
                  use tax or any tax in lieu thereof imposed by any local,
                  state, or federal government or governmental agency with
                  respect to the Services or with respect to this Agreement, but
                  in no event will taxes be paid by HighwayMaster which are
                  based on the income or net worth of SBMS.

         11.17.   Third Parties. Except as expressly provided herein, nothing
                  herein expressed or implied is intended or shall be construed
                  to confer upon or give to any individual or entity other than
                  the parties hereto and their successors or permitted assigns,
                  any rights, benefits or remedies of any kind or character
                  whatsoever under or by reason of this Agreement.

         11.18.   Attorneys' Fees. Except as herein expressly provided, in any
                  arbitration, suit, action or proceeding brought by one party
                  against the other party under this Agreement, or where any
                  provision hereof is validly asserted as a defense, the
                  prevailing party shall be entitled to recover reasonable
                  attorneys' fees in addition to any other available remedy,
                  subject to the limitation of liabilities set forth herein.


ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 17


   18

         11.19.   Independent Contractor. SBMS is providing the Services as an
                  independent contractor. This Agreement shall not be construed
                  to create a joint venture, partnership, employment
                  relationship, franchise or any other legal relationship
                  between the parties other than that of independent contractor.
                  Neither party shall share or be responsible for the debts and
                  liabilities of the other party, or have the authority to bind
                  the other party in any manner.

         11.20.   Entire Agreement. This Agreement, together with all Exhibits
                  attached hereto and expressly made a part of this Agreement,
                  shall constitute the entire agreement between the parties
                  hereto with respect to the Services and shall supersede all
                  prior proposals, negotiations, understandings and agreements,
                  whether oral or written.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed
as of the date first above written.


HIGHWAYMASTER CORPORATION,
A DELAWARE CORPORATION


By: (x) William H. McCausland
   -----------------------------

Name: William H. McCausland
     ---------------------------

Title: Sr. V. P. - Operations
      --------------------------

Date: March 30, 1999
      --------------------------


SOUTHWESTERN BELL
MOBILE SYSTEMS, INC.
A VIRGINIA AND DELAWARE CORPORATION


By: (x) Lisa Guarnacci for Frank Boyer
   -----------------------------

Name: Frank Boyer
     ---------------------------

Title: V. P. Product Development
      --------------------------

Date: March 30, 1999
      --------------------------


ADMINISTRATIVE CARRIER AGREEMENT
PAGE - 18



   19



                                    EXHIBIT 1

                ADDENDUM TO INTERCARRIER ROAMER SERVICE AGREEMENT

         This Addendum is made by and between SOUTHWESTERN BELL MOBILE SYSTEMS,
INC. on behalf of itself and its affiliates ("SBMS") AND [FILL IN CARRIER NAME],
on behalf of itself and its affiliates ("CARRIER").

         WHEREAS, SBMS has signed an Administrative Carrier Agreement ("ACA")
with HighwayMaster Corporation ("HighwayMaster");

         WHEREAS, Carrier desires to facilitate the provision of cellular roamer
service to end users of the HighwayMaster System and has signed or intends to
sign a Cellular Service Agreement with HighwayMaster to set rates and other
terms and conditions of the service to be provided by Carrier to HighwayMaster's
end users;

         WHEREAS, in recognition of the unique requirements of HighwayMaster's
end users, including members of the long haul trucking industry and other
similarly situated industries with nomadic travel patterns, the Parties hereto
have assented to amend the IRSA(s) in accordance with the provisions set forth
herein;

         NOW, THEREFORE, it is agreed as follows:

1.   This Addendum shall amend the Intercarrier Roamer Service Agreement(s)
     listed on Attachment A hereto (the "IRSA(s)"), along with any replacement
     intercarrier roamer service agreements intended to replace, modify or
     supersede the IRSAs. The provisions set forth herein are incorporated by
     reference and shall become a part thereof. In the event that the IRSA(s) is
     assigned in accordance with its terms, this Addendum shall be assigned
     along with the IRSA(s).

2.   Pursuant to the provisions herein stated, Carrier agrees for the term of
     this Addendum to provide roaming service in accordance herewith in those
     cellular markets set forth on Attachment B at the rates established by and
     between Carrier and HighwayMaster. It is expressly understood and agreed
     that SBMS shall have no responsibility for negotiating or setting rates for
     the service to be provided by Carrier to HighwayMaster End Users.

3.   SBMS is providing administrative and settlement functions for
     HighwayMaster. SBMS shall participate with Carrier in the net settlement
     process and provide the settlement funding account with respect to the
     HighwayMaster BID(s). Notwithstanding the foregoing, HighwayMaster is the
     party ultimately responsible for all of the cost of services for system
     usage on Carrier's systems, at the rates set between HighwayMaster and
     Carrier. Therefore, both parties agree that any disputes or adjustments
     regarding Carrier's charges with respect to the HighwayMaster BID(s) shall
     be handled directly between Carrier and HighwayMaster, and that any
     mechanisms created by CIBERNET to adjust charges related to billing through
     the Net Settlement Program will not be used with respect to the
     HighwayMaster BID. HighwayMaster shall be entitled to seek amounts for any


                                       1

   20

     overcharges directly from Carrier, and Carrier shall be required to seek
     amounts for any undercharges directly from HighwayMaster, and not SBMS.

4.   SBMS shall notify Carrier of the NPA/NXX combinations created solely for
     use by roamers as defined herein, which NPA/NXXs will be associated with a
     unique HighwayMaster billing identification ("BID") assigned to SBMS. The
     NPA/NXX's are not dialable from the Public Switched Telephone Network and
     can only be successfully called through the HighwayMaster Network Services
     Center. The HighwayMaster BID will be used nationally to identify vehicles
     equipped with the HighwayMaster system. HighwayMaster will provide Carrier
     with all updates of NPA/NXXs used for the purposes of this application.
     HighwayMaster will provide Industry Standard Updates which shall be listed
     on HighwayMaster's Technical Data Sheets. All assigned numbers will be
     stored in a validation database, jointly maintained by TSI and
     HighwayMaster. HighwayMaster shall provide activations, ESN changes and
     updates to the database.

5.   Term and Termination.

     5.1. The term of this Addendum shall commence on the later of (a) the
          Cutover Date under the ACA (which shall be no later than December 20,
          1999); (b) the effective date of the Cellular Service Agreement
          between Carrier and HighwayMaster; or (c) the date that the
          HighwayMaster BID and NPA/NXXs are transferred from HighwayMaster's
          current administrative carrier to SBMS; and shall continue for an
          Initial Term of one (1) year. Thereafter, it shall renew for
          successive one year terms, provided that either Party may terminate
          this Addendum by providing written notice of termination to the other
          at least sixty (60) days prior to the end of the Initial Term or any
          Renewal Term.

     5.2. This Addendum shall automatically terminate with respect to any
          Carrier markets covered by an IRSA that expires or is terminated and
          not replaced or superseded with another intercarrier roamer service
          agreement between SBMS and Carrier.

     5.3. SBMS may terminate this Agreement immediately upon written notice to
          Carrier that: (a) the ACA between SBMS and HighwayMaster has
          terminated; or (b) HighwayMaster has notified SBMS that the Cellular
          Service Agreement between Carrier and HighwayMaster has terminated.
          For purposes of this section, SBMS shall be entitled to rely solely on
          notification from HighwayMaster with respect to whether the Cellular
          Service Agreement between Carrier and HighwayMaster has terminated.

6.   Neither Party hereto shall be liable to the other Party or any third party,
     including affiliates, subsidiaries or partnership interests, for indirect,
     incidental, consequential, reliance or special damages, including, without
     limitation, damages for lost profits, regardless of the form of action
     whether in contact, indemnify, warranty, strict liability or tort arising
     from or related to the performance of the duties of either Party in
     accordance with the terms set forth herein or the rendering of services
     hereunder.

7.   The Parties agree that HighwayMaster is an intended third-party beneficiary
     of this Addendum.


                                       2

   21

8.   To the extent that the provisions of the Addendum conflict with the
     IRSA(s), this Addendum shall control.

9.   This Addendum may only be modified by written agreement of the Parties
     hereto.


Southwestern Bell Mobile Systems, Inc.      [CARRIER NAME]


By:                                         By:
   -------------------------------             -------------------------------

Name:                                       Name:
   -------------------------------             -------------------------------

Title:                                      Title:
   -------------------------------             -------------------------------

Date:                                       Date:
   -------------------------------             -------------------------------



                                       3