; (B) the horizontal or vertical realignment of a highway; (C) the installation (as distinguished from cleaning, repair, or replacement in kind) of a bridge, culvert, or other drainage structure or conduit; or (D) any significant change in the surface composition of a highway. (11) Maintenance The term maintenance means the preservation of an existing highway, including— (A) the physical upkeep of the highway; (B) the repair or replacement of wear or damage to the highway, including bridges, culverts, or other drainage structures or conduits, from natural or other causes; (C) the restoration of the shape of the highway; and (D) the gradation of the highway or other measures to ensure that the shape of the highway permits drainage. (12) Public land The term public land means land— (A) that is owned, controlled by, or subject to the jurisdiction of the Federal Government for the benefit of the public; and (B) that was not reserved on the date on which a R.S. 2477 right-of-way grant was accepted. (13) Public or public user (A) In general The terms public or public user mean all natural persons, including Federal lessees, permitees, licensees, invitees, and any other natural person that holds an authorization or is otherwise allowed to enter or use public land. (B) Exceptions The terms public or public user do not include any Federal agent or employee acting within the scope of the employment of the Federal agency or employee. (14) R.S. 2477 The term R.S. 2477 means section 2477 of the Revised Statutes ( 43 U.S.C. 932 ) repealed by section 706 of the Federal Land Policy and Management Act of 1976 ( Public Law 94–579