8830.1400 FLASHING LIGHT UNITS.
Flashing light units consist of two horizontally mounted red lights flashing alternately at predetermined levels. Design criteria for flashing light units must comply with the AREMA signal manual.
Horizontal and vertical installation.
Flashing light units must be mounted in accordance with the MMUTCD. Use of cantilevered flashing light units that are mounted on the arm projecting over the roadway must comply with the MMUTCD.
Size and design.
Lamp units must be 12 inches (300 millimeters) in diameter, must be hooded to shade them from the sun but not shielded at the sides to impair close-in indication, and must have nonreflecting black backgrounds 20 to 24 inches (500 to 600 millimeters) in diameter. The light units must flash alternately. The number of flashes per minute for an incandescent-type lamp must comply with the MMUTCD. Lamps must be illuminated approximately the same length of time.
Alignment of flashing light units must be accomplished by the rail carrier in accordance with the recommended practice set forth in Code of Federal Regulations, title 49, section 234.217, paragraph (a), as amended.