Contrary to the familiar red, yellow, and green lights we're all familiar with, the world's first traffic signal was a rudimentary gas-powered contraption. It was installed in London in 1868 at ...

The earliest traffic signal that used red and green lights was installed in London in 1868. The inventor, railroad engineer J.P. Knight, used semaphore arms during the day and gas lamps to ...

On December 1868, the world's first traffic signal was installed at the ... reduced by more than 25 percent and wait times at red lights have down an average of about 40 percent decreasing emissions.