The first traffic light was illuminated with gas lamps.

Science & Industry

T raffic accidents were a problem long before motor vehicles dominated the road — pedestrians, horses, and carts all competed for the right of way, sometimes with fatal results. In fact, the first traffic signal in Britain predated cars: Railroad engineer John Peake Knight helped design signaling systems for trains, including semaphore signals, which employed a movable arm to indicate whether a train operator should stop. Knight proposed that these signals could work on city streets, too, with gas lamps for nighttime visibility.

After the plan received government approval, the first gas traffic light was installed in London on December 9, 1868, just outside the Houses of Parliament. This being Victorian England, it was ornately decorated, with a hollow cast-iron column adorned with gilding and acanthus leaves. Above the signal arms, an octagonal box with a pineapple finial contained red and green gas lamps. Automated lights were still several decades away, so the signal had to be manually operated by a police officer 24 hours a day. The light was successful at first, and drivers, for the most part, actually paid attention to it. But the very next month, a leaky pipe filled the hollow tower with gas and caused an explosion that severely injured the officer operating it. London didn't get traffic lights again until electric lights were installed in 1929.

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By the Numbers

Estimated daily commuters to London from outside towns in 1850

27,000

Driving trips the average American takes every day

2.44

Did you know?

The first three-way traffic signal was invented in 1923.

The first electric traffic lights typically went straight from red to green and green to red with no warning signal indicating how soon the light was going to change. A Detroit police officer introduced yellow lights to one intersection in 1920, but they were far from widespread. Two years later, another three-way traffic signal was invented by Garrett Morgan, a pioneering Black inventor from Cleveland, Ohio. Morgan had already created a lifesaving precursor to the gas mask and an improved sewing machine when he witnessed a carriage accident at a problematic intersection in Cleveland. Troubled by the incident, he created a T-shaped illuminated traffic signal that had a third setting that instructed traffic in all directions to stop, which served as a warning for drivers to fully clear the intersection and also gave pedestrians a chance to cross safely. The signal was influential and widely used, and Morgan made $40,000 from it, around $700,000 in today's dollars, when he sold the patent to General Electric.