The first traffic light was operated by a policeman in 1868 and it was the only way things worked for a while.
Modern traffic control systems are implemented with microcontrollers, networks and software.
But what are the first mechanisms that allowed to free the traffic police from the mundane task of directing the traffic?
Was there a sort of an electric or mechanical timer? If so, how did it work? How were the automatic traffic lights synchronized?
All solutions that predate digital electronics are welcome.