(a) New, used and remanufactured commuter rail cars, to be considered accessible by regulations in part 37 of this title, shall comply with this subpart.(b) If portions of the car are modified in such a way that it affects or could affect accessibility, each such portion shall comply, to the extent practicable, with the applicable provisions of this subpart. This provision does not require that inaccessible cars be retrofitted with lifts, ramps or other boarding devices.(c)(1) Commuter rail cars shall comply with §§ 38.93(d) and 38.109 of this part for level boarding unless structurally or operationally impracticable.(2) Where level boarding is structurally or operationally impracticable, commuter rail cars shall comply § 38.95 of this part.(d) Existing vehicles retrofitted to comply with the "one-car-per-train rule" at § 37.93 of this title shall comply with §§ 38.93(e) , 38.95(a) and 38.107 of this part and shall have, in new and key stations at least one door on each side from which passengers board which complies with § 38.93(d) of this part. Vehicles previously designed and manufactured in accordance with the program accessibility requirements of section 504 of the Rehabilitation Act of 1973, or implementing regulations of the Secretary of Transportation that were in effect before October 7, 1991; and which can be entered and used from stations in which they are to be operated, may be used to satisfy the requirements of § 37.93 of this title.56 FR 45756, Sept. 6, 1991, as amended at 76 FR 57939 , Sept. 19, 2011