49 CFR § 222.23 - How does this regulation affect sounding of a horn during an emergency or other situations?
(1) Notwithstanding any other provision of this part, a locomotive engineer may sound the locomotive horn to provide a warning to animals, vehicle operators, pedestrians, trespassers or crews on other trains in an emergency situation if, in the locomotive engineer's sole judgment, such action is appropriate in order to prevent imminent injury, death, or property damage.
(2) Notwithstanding any other provision of this part, including provisions addressing the establishment of a quiet zone, limits on the length of time in which a horn may be sounded, or installation of wayside horns within quiet zones, this part does not preclude the sounding of locomotive horns in emergency situations, nor does it impose a legal duty to sound the locomotive horn in such situations.
(b) Nothing in this part restricts the use of the locomotive horn in the following situations:
(1) When a wayside horn is malfunctioning;
(2) When active grade crossing warning devices have malfunctioned and use of the horn is required by one of the following sections of this chapter: §§ 234.105, 234.106, or 234.107;
(3) When grade crossing warning systems are temporarily out of service during inspection, maintenance, or testing of the system; or
(4) When SSMs, modified SSMs or engineering SSMs no longer comply with the requirements set forth in appendix A of this part or the conditions contained within the Associate Administrator's decision to approve the quiet zone in accordance with section 222.39(b) of this part.
(c) Nothing in this part restricts the use of the locomotive horn for purposes other than highway-rail crossing safety (e.g., to announce the approach of a train to roadway workers in accordance with a program adopted under part 214 of this chapter, or where required for other purposes under railroad operating rules).