Mars Lights are signal-safety lights used in the United States and built by Mars Signal Light Company for railroad locomotives and firefighting apparatus. Mars Lights used a variety of means to cause the light to oscillate vertically, horizontally, or both, to catch the attention of motorists and pedestrians.
Mars lights were developed by Jerry Kennelly, a Chicago firefighter who realized that oscillating lamps would benefit fire departments and railroads. He performed an operational test with the Chicago and North Western railroad in 1936, and Mars Lights began appearing on locomotives in the later 1930s.
Tri Lite, Inc. announced its acquisition of the Mars Signal Light Company, on January 23, 1991. Tri Lite still manufactures many of the traditional Mars Lights under the Tri Lite Mars brand. The company has since updated the Mars "888" Traffic Breaker with energy-efficient LEDs replacing the earlier sealed beam halogen/incandescent lamp.