A marker light using an array (2) of light emitting diodes (12) in combination with lenses (3) provides a light beam of required intensity, shape and color for railroad applications. The light emitting diodes are arranged in various configurations to form the array (2). The lenses may be Fresnel lenses. Control circuitry (C) energizes the light emitting diodes at predetermined or variable flashing rates. Sensing circuitry (222) senses the failure of light emitting diodes in the array and provides an indication of such failure.