Ditch lights => luzes de sinalização

"Ditch light" refers to the "ditch" or area of the right-of-way located immediately forward of the locomotive, to either side of the track that this light illuminates. These lights are designed to increase the visibility of the train crews themselves, thus providing an added margin of safety against potential hazards that might exist in those areas. This explains, also, the use of a wider focal angle than that recommended for "crossing lights."
http://www.trainweb.org/gyra/dc_lts.htm

GE AC4400 Athearn RTR - YouTube
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www.youtube.com/watch?v=4shWoXGhF9s12 Oct 2010 - 2
Para evitar danos a carcaça e a pintura, deixei de instalar as luzes de sinalização (ditch light), porem o ...

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Note added at 5 hrs (2012-06-28 21:17:11 GMT)
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Ditch Lights are not the same as crossing lights "luzes de cruzamento ou faróis de cruzamento"

On the other hand, as the name would seem to imply, "crossing lights" are used as much to provide a warning to motor vehicle operators located at highway/rail intersections at grade some distance ahead of an approaching train in its direction of travel as they are to provide better visibility for the train crews. In order to accomplish this a narrower focal angle is used to ensure that the light can be seen far enough up the track in advance of the arrival of the train at the crossing that it can provide adequate warning.

Generally, ditch lights are used in a steady burn mode. Crossing lights are set to flash at a minimum of 40 flashes per minute (maximum 180 flashes per minute).
http://www.trainweb.org/gyra/dc_lts.htm