Vintage Cars: Acetylene lamps, electrical lighting, lighting system

Question
When did acetylene lamps cease to be used on cars?

Answer
There is no exact date as to when they were last used, as the electric light on automobiles was "phased in" through improvements, eventually becoming superior to acetylene.  The first electric lights on automobiles were introduced just before 1900, and the first fully-integrated electrical lighting system appeared on the 1912 Cadillac.  Acetylene lights had all but disappeared from vehicles by the end of WWI.