On December 10, 1868, the first ever traffic signal was erected just outside the British Houses of Parliament in London. It was quite simply revolutionary. Traffic levels on city streets were reaching dangerous levels of congestion and speed that began to threaten the safety of pedestrians and horses and their drivers. At first, planners saw the obvious remedy as constructing webs of over and underpasses to allow for uninterrupted traffic flows that removed the need for tricky intersections. It would take something of a visionary for the time to come up with the idea for the traffic signal.
John Peake Knight grew up working on the railroad. After leaving school at 12 to work in the parcel department of a railroad company, he worked his way up to higher and higher posts until he was the superintendent of an entire company by just 25 years old. Not long after this, he came up with the idea of applying railroad signaling technology and methodology to the busy streets of London. He approached the head of the London Police about trying out his new concept and it would seem the meeting went well as he was soon installing his signal in one of the most notable location in the city.
The design was simple. The single post had two swinging arms projecting out from a main box. The arms could be raised and lowered to indicate the status of the intersection: lowered meant you were free to pass through, raised halfway meant slow and caution, and fully horizontally extended indicated you were to come to a full stop to allow traffic from the other direction to pass. The signal wasn’t meant to eliminate any jobs, as it had to be hand operated by a policeman using levers, but it did work well to control traffic flow at this busy intersection.
Trouble came when one of the more innovative features of the signal failed in a rather catastrophic fashion. To solve the problem of the signal arms being all but invisible by nightfall, Knight had installed something much closer to our modern signals than the semaphore arms: a colored gas lamp that could change between green and red. Drivers could easily see this lantern by night, and the police officer could easily switch the colors back and forth to control traffic flow. The problem arose when the gas main that fed a steady stream of the volatile substance into the lantern leaked and sparked an explosion at the signal. The unlucky policeman working that evening suffered severe burns and the entire project was abandoned.
While the end of Knight’s traffic signal came swiftly - around a month after it had been installed - it wasn’t actually due to anything wrong with the concept or implementation. As we have seen, traffic signals have become an integral part of road systems around the globe. Once electric power was available to power the lights they started to become commonplace as dangerous gas was no longer required. Perhaps the most lasting contribution Knight gave to the world of automotive travel, once we settled on lights both in the daytime and night, was the concept that red means stop, and green means go.