Mars Lights are signal-safety lights used in the United States and built by Mars Signal Light Company for railroad locomotives and fire 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 C&NW railroad in 1936, and Mars Lights began appearing on locomotives in the 1940s.
Tri Lite, Inc. announced their acquisition of the Mars Signal Light Company effective January 23, 1991. Tri Lite still manufactures many of the traditional Mars Lights under the Tri Lite Mars brand. The company has recently updated the Mars "888" Traffic Breaker with energy efficient LED bulbs.
There were many models of Mars Lights, which used several methods to oscillate the beam. Sometimes the bulb and assembly were moved, other times a reflector behind the light was rotated. The beam was usually rotated in a triple eight pattern, providing a source for the company slogan, "The Light from Mars". The beams came in a variety of shapes and colors, some locomotives having red and white lights.
Many railroads used Mars lights on a variety of locomotives, both steam and diesel. Mars lights are no longer used by railways, having been replaced by ditch lights, with the exception of some passenger carriers, such as Chicago's Metra. They are still used on fire fighting apparatus, and are available from Tri Lite / Mars, located in Chicago, Illinois.
Gyralite is a similar type of gyrating warning light formerly made by The Pyle-National Company and now by Trans-Lite, Inc.
- Grant V.W. Roth (November 1990) Mainline Modeler "Mars Lights; Their Development"