49 CFR § 236.531
Trip arm; height and distance from rail
November 18, 2020
Trip arm of automatic train stop device when in the stop position shall be maintained at a height above the plane of the tops of the rails, and at a horizontal distance from its center line to gage side of the nearest running rail, in accordance with specifications of the carrier.
[49 FR 3386, Jan. 26, 1984]