Highway-Rail Grade Crossing Advance Warning, Color
A Highway-Rail Grade Crossing Advance Warning sign shall be used on each highway in advance of every highway-rail grade crossing except in the following circumstances:
A. On an approach to a highway-rail grade crossing from a T-intersection with a parallel highway, if the distance from the edge of the track to the edge of the parallel roadway is less than 30 m (100 ft), and signs are used on both approaches of the parallel highway; or
B. On low-volume, low-speed highways crossing minor spurs or other tracks that are infrequently used and are flagged by train crews; or
C. In business districts where active highway-rail grade crossing traffic control devices are in use; or
D. Where physical conditions do not permit even a partially effective display of the sign.
Federal Highway Administration Manual on Uniform Traffic Control Devices for Streets and Highways, 2003 Edition (including 2004 and 2007 revisions) (Washington, DC: United States Department of Transportation, 2007)