A lighting system for exterior lights of an automobile comprises a first lighting unit (10,12,14,16) primarily for outputting a first automotive light signal and a failure detection system (26) for detecting a failure of the first lighting unit (10,12,14,16). A second lighting unit is primarily for outputting a second automotive light signal. The second lighting unit comprises an LED light unit. A controller (30) is adapted to determine if there is failure of the first lighting unit, and if there is failure of the first lighting unit, to use the second lighting unit to generate the first automotive light signal. This is in response to an output request from the first lighting unit (10,12,14,16).