Most people want to know about why they invented the traffic light before the car.  The very first was installed in London, England in 1868.  The whole purpose of the traffic light is because it was supposed to keep people from being trampled by horses.  It was created by a railroad engineer.  During the day it looks like arms going up and down instead of what we have today which is a red light, green light and yellow light.  They mean:

     The first traffic lights were terrible.  They did more damage than not.  After a short time of its use, it exploded and killed most or all of the policemen that were operating the lever.  They didn’t do any experiments for 50 years.  In 1914 when the automobile was invented, the traffic light was reinstated.  The first to be reinstated was in Cleveland, Ohio.  The traffic light only had two lights.  One was, of course, red and the other green.  The three-color light was first in New York, New York, in 1918.  Not until 1926 did they invent the automatic traffic light.  That is what we use today with three lights.