49 CFR 229.46 - Brakes: general.
(a) Before each trip, the railroad shall know the following:
(1) The locomotive brakes and devices for regulating pressures, including but not limited to the automatic and independent brake control systems, operate as intended; and
(2) The water and oil have been drained from the air brake system of all locomotives in the consist.
(b) A locomotive with an inoperative or ineffective automatic or independent brake control system will be considered to be operating as intended for purposes of paragraph (a) of this section, if all of the following conditions are met:
(2) The railroad has previously determined, in conjunction with the locomotive and/or airbrake manufacturer, that placing such a locomotive in trailing position adequately isolates the non-functional valves so as to allow safe operation of the brake systems from the controlling locomotive;
(3) If deactivation of the circuit breaker for the air brake system is required, it shall be specified in the railroad's operating rules;
(4) A tag shall immediately be placed on the isolation switch of the locomotive giving the date and location and stating that the unit may only be used in a trailing position and may not be used as a lead or controlling locomotive;
(6) The inoperative or ineffective brake control system is repaired prior to or at the next periodic inspection.