Before automobiles even swarmed over the roads and streets, there was a need to control traffic to avoid accidents and keep vehicles moving smoothly.
The current systems have developed over more than a century, and they’re poised to change once again as vehicles become more connected and traffic control moves toward AI and complex computer-driven systems.
A signal history
December 10, 1868 — The first gas-lit traffic lights were installed outside the Houses of Parliament in London. Proposed by British railway engineer J.P. Knight to control the traffic of horse carriages, gas lights were manually controlled by a police officer using semaphore arms. At night, gas-lit red and green lights were used, but still changed by a police officer. The lights became a safety hazard as they sometimes exploded and injured police officers.
1912 — A traffic control device was placed on top of a tower in Paris at the Rue Montmartre and Grande Boulevard, with a revolving four-sided metal box on top of a glass showcase where the word “Stop” was painted in red and the word “Go” painted in white.
1912 — As automobile traffic increased, American policeman Lester Wire designed the first electric traffic light. It was first installed in Cleveland, Ohio, on August 5, 1914, at the corner of 105th and Euclid Avenue.
1917 — First interconnected traffic signal system installed in Salt Lake City, with six connected intersections controlled simultaneously from a manual switch.
1920 — William Potts, a Detroit policeman, invented the first four-way and three-colored traffic lights. He introduced yellow lights to indicate the light would change soon. Detroit became the first city to implement the four-way and three-colored traffic lights.
1920 — Los Angeles installs five signals on Broadway manufactured by the Acme Traffic Signal Co. The signals paired “Stop” and “Go” semaphore arms with small red and green lights and bells that rang just before the flags changed.
1920s — In a predominately Irish neighborhood in Syracuse, New York, traffic lights were vandalized frequently. The Irish citizens objected to the red light on top, which they viewed as a symbol of British oppression of Ireland (represented by green lights at the bottom). City officials flipped the signals in that neighborhood to have green lights on top.
1923 — Garrett Morgan received a patent for an electric traffic signal. The African American inventor owned a sewing machine company in Cleveland and, after witnessing a horrific accident, worked on his automated traffic signal system. GE paid him $40,000 for the invention.
1928 — Charles Adler Jr. developed a sonically actuated traffic light. To operate it, drivers pulled up to a red light and honked their horns to make the light change. Installed in Baltimore, it was the first actuated traffic signal in the United States and served as the basis for modern traffic signals.
1929 — Adler also invented a pedestrian push button, which was installed in Baltimore—the first pedestrian-actuated signal.
1950s — Computerized detection used in traffic lights. A pressure plate was placed at intersections so computers would know that a car was waiting at the red light.
1960s — As computers improved, they could monitor traffic and change lights in an even more efficient way.
1990s — The countdown timer was introduced to traffic lights to help pedestrians know whether they have enough time to cross the road before the signal changes color.
2010s — Connected vehicles can communicate with traffic signals and other vehicles. This can vastly improve speed, timing, and efficiency at intersections—perhaps as much as 40 percent as more vehicles get connected, according to Washington State University research.
Future — Connected vehicles and AI-driven traffic control could lead to another color in the traffic signal: blue. “We need a new signal called blue phase, meaning you should follow the vehicle in front of you,” says civil engineer and traffic control researcher Ali Hajbabaie, explaining that connected vehicles can more work with signal system to keep traffic moving while human drivers could follow them during the blue phase.
Further reading
Smart signals (WSM, Fall 2019)
Car Country: A Environmental History. Christopher W. Wells, 2014, University of Washington Press
Onramps and Overpasses: A Cultural History of Interstates. Dianne Perrier, 2009, University of Florida Press
Door to Door: The Magnificent, Maddening, Mysterious World of Transportation. Edward Humes, 2016, Harper.
Visions for Tomorrow’s Mobility (smart magazine)
Traffic light (Wikipedia)
Ready, Steady, Go: The evolution of traffic lights (Science ABC)
Charles Adler, Jr. (Wikipedia)
The first traffic signal was invented in 1868 by J.P. Knight. In 1912, the first electric traffic light was invented by Lester Wire. The modern traffic light still uses this T-shaped model with three different colors. Computers are used to predict traffic and change lights accordingly.
Imagine a set of people having a heated discussion in a closed room. The conversation can turn into a complete mess if there is no coordinator to look after these people and guide the chatter. In such a situation that isn’t controlled, all we would hear is random shouting and noise, as no one would want to be left behind, so everyone would try to express his/her point of view without considering what the other person has to say. This kind of situation would ultimately lead to total chaos.
Now, imagine the same situation taking place on our roads, and simply replace the set of people with vehicles. If people were to drive their cars randomly without caring about or considering other vehicles on the road, it could lead to chaos and may result in accidents; the end result can be catastrophic.
Enter traffic lights, which play the role of coordinators on the road. They control the flow of the ever-increasing number of automobiles on the road and they also help in preventing accidents.
Let’s take a closer look at how traffic lights have evolved over time.
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The First Traffic Signal
Although the purpose of a traffic signal is to regulate the flow of automobiles, traffic signals came into existence long before automobiles were invented. The idea for developing traffic signals began in the 1800’s, and on December 10, 1868, the first gas-lit traffic lights were installed outside the Houses of Parliament in London. This model was proposed by a British railway engineer, J.P Knight. It was implemented to control the traffic of horse carriages in the area, and to allow pedestrians to safely cross the roads.
The gas-fueled lights needed to be manually controlled by a police officer using semaphore arms. During the daytime, the semaphore arms would be raised or lowered by the police officer, signaling vehicles whether they should proceed or stop. At night, instead of arms, gas-lit red and green lights were used. Red signaled carriages to stop, and green meant proceed. Red was used to stop, as it represented danger or caution, whereas green was determined to be a more reassuring color in most cultures and also has a strong emotional correspondence with safety.
As these were gas-lit lights, there were some incidents of lights exploding at night and injuring police officers who were controlling them. Therefore, the gas-lit traffic lights were not entirely safe to use.
The First Electric Traffic Lights
In the early 1900’s, the world was developing at a very rapid pace, and with the growth of industrialization, cities became more crowded. Furthermore, with the invention of automobiles, the traffic on the roads increased significantly, so there was a need for a better traffic system.
In 1912, an American policeman, Lester Wire, who was concerned with the increasing traffic, came up with the idea of the first electric traffic light. Based on Wire’s design, the lights were first installed in Cleveland, Ohio, on August 5, 1914, at the corner of 105th and Euclid Avenue.
At that time, it was said that this invention would revolutionize the handling of traffic in congested cities. As it turned out, the modern traffic system still works on the same principle as Wire’s original system. The momentous occasion of the first electric traffic light turning 101 years old on August 5, 2015 was celebrated by Google Doodle.
The first electric traffic light had only red and green lights; it did not have a yellow light like modern-day traffic signals. Instead of a yellow light, it had a buzzer sound that was used to indicate that the signal would be changing soon.
The First Four-way and Three-colour Traffic Lights
In the year 1920, a policeman named William Potts in Detroit, Michigan invented the first four-way and three-colored traffic lights. Apart from red and green, a third color – amber (or yellow) – was introduced. Detroit became the first city to implement the four-way and three-colored traffic lights. The idea of having a third “warning” light, was also patented by African-American inventor, businessman Garrett Augustus Morgan, Sr. in the year 1923. In the 1920’s, several automated traffic signals were installed in major cities around the world. The modern traffic light still uses this famous T-shaped model with three different colors.
Traffic Lights That Detect Vehicle Honks
The automated traffic signals were a big success; they operated by changing their lights at fixed intervals of time. This sometimes caused unnecessary waiting for vehicles, as the light would be red, even when there were no vehicles passing from the opposite side. People eventually began trying to invent a better traffic signal system that could allow for an even smoother flow of traffic.
An inventor named Charles Adler Jr. had the idea of inventing a signal that could detect vehicles’ honking and change signals accordingly. A microphone was mounted on the pole of the signal, and once the vehicle reached the signal, all it needed to do was honk and the light would change. However, this obviously led to the problem of unnecessary honking of vehicles, which created a harrowing experience to those walking by and those living near the signal. Thus, the honk-sensitive lights had to be abolished.
The Computerization of Traffic Lights
In the 1960’s, with the invention of computers, traffic lights started to become computerized. Over time, computers improved, and the traffic lights subsequently improved, and they could now monitor traffic and change lights accordingly. Based on the software, the traffic of a city could now be predicted and accordingly controlled.
At present, traffic all over the world can be monitored, which gives an idea about the traffic at a certain time, which city has the most traffic, and what the peak hours of traffic are, so the lights can be controlled accordingly. The computer also monitors the weather and their operation can be changed depending on the weather. The lights can also be adjusted in the case of emergencies, so computers have vastly improved the handling of traffic and increased total road safety.
Countdown Timer
The countdown timer was introduced to traffic lights in the 1990’s. The countdown timer helps pedestrians know whether they have enough time to cross the road before the signal changes color.
Rain Sensing Lights
City of Rotterdam in the Netherlands has introduced bicycle traffic lights fitted with a rain sensor. When it is raining, these lights give higher priority to bicycle lanes at an intersection.
The Future of Traffic Lights
The number of vehicles on the road has been drastically increasing every year and will continue to increase, so traffic signals must continue to improve to accommodate these higher amounts of traffic.
Connected Vehicles
In the future, we will have connected vehicles that would be able to communicate with traffic signals and other vehicles. As the cars would be able to communicate with traffic signals, this would allow them to know whether they can make it in time to the next signal before it turns red; the signal can also urge you to speed up in order to make the signal on time.
Eventually, a time will come when signals will ask the cars where they are going and change traffic plans accordingly.
Traffic signals will improve over time, there is no doubt about that, and they will continue to provide safer and faster commutes for vehicles. However, it will still all be a waste if we don’t follow traffic rules. Most accidents occur as a result of breaking traffic rules, so on the 101st anniversary of traffic lights, let’s make a pledge to follow traffic rules to ensure a smooth and safe drive for everyone on the road!
Suggested Reading
References
- Traffic Light - Wikipedia
- The Guardian
- Georgia Tech
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