The image above is an animated GIF of a higher resolution image of the Google logo, aka Doodle, on Google's home page today. It is to remember the day the first traffic light was installed, which was 101 years ago today.
On August 5th, 1914 the first electronic light was installed in Cleveland, Ohio at the corner of 105th and Euclid. The American Traffic Signal Company was the company behind this first signal. It had two colors, red and green, and a buzzer.
Prior there were Gas-lit stoplights, but they didn't work too well and often exploded. These were installed in 1868 in London. This was to solve a problem of road congestion with both automobiles on the road, as well as horse and buggies.
Google said on the Google doodle page:
Doodler Nate Swinehart hearkens back to an earlier time with shades of black and white, and uses the background colors to make the red and green signals particularly luminous. It’s not an artistic coincidence that the cars leap forward and screech wildly to a halt, either--the yellow light wouldn’t appear for several years, and overzealous motorists had to stop on a dime.
Forum discussion at Google+.