Topic summary
Traffic signals
Extracted from the Wikipedia article Traffic light.
History
In December 1868, the first traffic signals showing a red or green light at night were installed outside the Houses of Parliament in London. They were invented by John Peake Knight. A police constable raised or lowered the semaphore arms and, at night, operated a lever to control the lights which drivers and pedestrians saw. This system exploded on 2 January 1869 and was taken down. This early traffic signal led to other parts of the world implementing similar traffic signal systems. In the first two decades of the 20th century, semaphore traffic signals like the one in London were in use all over the United States. These traffic signals were controlled by a traffic officer who adjusted the signals to direct traffic.