<PAGE>   1

                                                                     EXHIBIT 4.7

                  SUPPLEMENTAL INDENTURE

                         SUPPLEMENTAL INDENTURE (this "Supplemental
                Indenture"), dated as of January 12, 2000, among
                TRAVEL PORT SYSTEMS, INC. (the "New Subsidiary
                Guarantor"), a subsidiary of TravelCenters of
                America, Inc. (or its successor), a Delaware
                corporation (the "Company"), THE COMPANY, on behalf
                of itself and the Subsidiary Guarantors (the
                "Existing Subsidiary Guarantors") under the Indenture
                referred to below, and STATE STREET BANK AND TRUST
                COMPANY, as successor to FLEET NATIONAL BANK, a
                national banking association, as successor trustee
                under the indenture referred to below (the
                "Trustee").

                              W I T N E S S E T H :


                  WHEREAS the Company has heretofore executed and delivered to
the Trustee an Indenture (the "Indenture"), dated as of March 27, 1997,
providing for the issuance of an aggregate principal amount of $125,000,000 of
10-1/4% Senior Subordinated Notes due 2007 (the "Securities");

                  WHEREAS Section 4.11 of the Indenture provides that under
certain circumstances the Company is required to cause the New Subsidiary
Guarantor to execute and deliver to the Trustee a supplemental indenture
pursuant to which the New Subsidiary Guarantor shall unconditionally guarantee
all of the Company's obligations under the Securities pursuant to a Subsidiary
Guaranty on the terms and conditions set forth herein; and

                  WHEREAS pursuant to Section 9.01 of the Indenture, the
Trustee, the Company and Existing Subsidiary Guarantors are authorized to
execute and deliver this Supplemental Indenture;

                  NOW THEREFORE, in consideration of the foregoing and for other
good and valuable consideration, the receipt of which is hereby acknowledged,
the New Subsidiary Guarantor, the Company, the Existing Subsidiary Guarantors
and the Trustee mutually covenant and agree for the equal and ratable benefit of
the holders of the Securities as follows:

<PAGE>   2

         1. DEFINITIONS. (a) Capitalized terms used herein without definition
shall have the meanings assigned to them in the Indenture.

         (b) For all purposes of this Supplement, except as otherwise herein
expressly provided or unless the context otherwise requires: (i) the terms and
expressions used herein shall have the same meanings as corresponding terms and
expressions used in the Indenture; and (ii) the words "herein," "hereof" and
"hereby" and other words of similar import used in this Supplement refer to this
Supplement as a whole and not to any particular section hereof.

         2. AGREEMENT TO GUARANTEE. The New Subsidiary Guarantor hereby agrees,
jointly and severally with all other Subsidiary Guarantors, to Guarantee the
Company's obligations under the Securities on the term and subject to the
conditions set forth in Article 11 of the Indenture and to be bound by all other
applicable provisions of the Indenture.

         3. RATIFICATION OF INDENTURE; SUPPLEMENTAL INDENTURES PART OF
INDENTURE. Except as expressly amended hereby, the Indenture is in all respects
ratified and confirmed and all the terms, conditions and provisions thereof
shall remain in full force and effect. This Supplemental Indenture shall form a
part of the Indenture for all purposes, and every holder of Securities
heretofore or hereafter authenticated and delivered shall be bound hereby.

         4. GOVERNING LAW. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT
GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT
THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

         5. TRUSTEE MAKES NO REPRESENTATION. The Trustee makes no representation
as to the validity or sufficiency of this Supplemental Indenture.

         6. COUNTERPARTS. The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.

         7. EFFECT AND HEADINGS. The Section headings herein are for convenience
only and shall not effect the construction thereof.

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

                                 TRAVEL PORT SYSTEMS, INC.

                                      by
                                          /s/  Andrew T. Panaccione
                                          ---------------------------
                                          Name:  Andrew T. Panaccione
                                          Title:  Secretary
<PAGE>   3

                                 TRAVELCENTERS OF AMERICA, INC.
                                 on behalf of itself and the Existing
                                 Subsidiary Guarantors,

                                      by
                                          /s/  James W. George
                                          --------------------
                                          Name:  James W. George
                                          Title:  Senior V.P. & C.F.O.

                                 STATE  STREET BANK AND TRUST COMPANY,
                                 as successor to FLEET NATIONAL BANK
                                 as successor Trustee,

                                      by

                                          /s/  Susan C. Merker
                                          --------------------
                                          Name:  Susan C. Merker
                                          Title:  Vice President