Molly Ayala
The electric automatic traffic light has undergone several iterations to reach its modern form. The first-ever traffic light was invented in London in 1868 by railway signalling engineer John Peake Knight. This traffic light was not electric and was likely operated by gas. The first electric traffic light was developed by policeman Lester Wire in 1912 and installed in Cleveland, Ohio in 1914. The first electric automatic traffic light was patented by Garrett Morgan in 1923, and the first four-way, three-colour traffic light was invented by police officer William Potts in Detroit, Michigan in 1920.
| Characteristics | Values |
|---|---|
| Year of Invention | 1912 |
| Inventor | Lester Wire |
| Inventor's Occupation | Policeman |
| Inventor's Workplace | Salt Lake City, Utah |
| Installation Date | 5 August 1914 |
| Installation Location | Corner of East 105th Street and Euclid Avenue, Cleveland, Ohio |
| Number of Colours | 2 |
| Colours | Red and Green |
| Other Features | Buzzer |
| Design Inspiration | Railroad Lights and James Hoge's Design |
| Patent Holder | James Hoge (in 1918) |
| Patent Number | 1,475,024 |
| Patent Date | 20 November 1923 |
| Improvements | Three-colour traffic light invented in 1920 by William Potts, a Detroit policeman |
| Recent Developments | Use of Light Emitting Diode (LED) lights in 1989 |
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What You'll Learn
The first electric traffic light
The introduction of electric traffic lights built on earlier traffic signals, which were non-electric and gas-lit. These early signals were first introduced in London in December 1868 to reduce the need for police officers to control traffic. Over time, the design of traffic lights evolved, and they became more advanced, with the introduction of automatic timers and computerised control systems.
In 1920, the first four-way, three-colour traffic light was created by police officer William Potts in Detroit, Michigan. This invention added a yellow "caution" light to the existing red and green lights. Potts' invention was soon adopted by cities across the United States and eventually around the world, becoming the global standard.
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Garrett Morgan's patent
Garrett Augustus Morgan, Sr. was an African-American inventor and community leader. He was born in 1877 in Kentucky and was the child of two formerly enslaved people. In 1907, he opened a repair shop, and in 1909 he added a garment shop to his operation. The business was very successful, and by 1920, Morgan had made enough money to start a newspaper, the Cleveland Call, which became one of the most important Black newspapers in the nation.
Morgan was one of the first inventors of traffic signals that are found all across the world today. He witnessed a serious accident at an intersection, which inspired him to invent an automated signal with an interim "warning" position—the ancestor of today's yellow light. This "all hold" position allowed drivers to have time to clear the intersection before crossing traffic entered it.
Morgan filed a patent for a traffic control device in 1922 and was granted Patent No. 1,475,074 on November 20, 1923, for his three-position traffic signal. His design used a T-shaped pole unit with three positions: "Stop", "Go", and "All Hold". The "All Hold" position regulated crossing vehicles more safely than earlier signals by stopping traffic in all directions to give drivers time to stop or get through the intersection.
Morgan's design could be produced inexpensively, thus increasing the number of signals that could be installed. He sold the rights to his traffic signal to General Electric for $40,000 (the equivalent of about $610,000 today).
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Early traffic light designs
The idea for developing traffic signals began in the 1800s, and the world's first traffic light was installed in London in December 1868. Proposed by railway engineer J.P. Knight, the design combined three semaphore arms with red and green gas lamps for night-time use, mounted on a 22-foot pillar. During the day, a police constable would manually turn the gas lantern with a lever, while at night, a red light meant "stop" and a green light meant "caution". This early attempt at traffic control was short-lived, as a gas leak caused an explosion that killed a police officer operating the signal.
It would be another 46 years until the first dual-coloured electric traffic light was installed in Cleveland, Ohio, in 1914. This was the first traffic light in the United States, and the first interconnected signal system was introduced in Salt Lake City in 1917. By the late 1920s, most US cities had implemented pre-timed systems, similar to those used today.
In 1908, Toledo, Ohio, introduced semaphore traffic signals with the words "Stop" and "Go" in white on a green background, with red and green lenses illuminated by kerosene lamps for night-time use. These signals were controlled by a traffic officer who would blow a whistle before changing the commands.
In 1912, the American Traffic Signal Company installed the first electric traffic lights in Salt Lake City and Detroit. These automated lights used red and green lights to signal "stop" and "go" and were manually operated by a policeman who would push a lever inside a control booth to change the lights.
In 1917, William Potts, a Detroit police officer, developed the first three-colour automatic traffic light system, adding a yellow "caution" light. This became the standard, allowing for clear signalling to automobiles and pedestrians.
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Traffic light evolution
The evolution of traffic lights began in 1868 when John Peake Knight, a railway signalling engineer in London, invented the first traffic light. It consisted of three semaphore arms with red and green lamps, operated by gas for night-time use. The first non-electric gas-lit traffic lights were installed outside the Houses of Parliament in London to control the traffic in Bridge Street, Great George Street, and Parliament Street.
In the early 20th century, semaphore traffic signals were popular in the United States, with each state adopting its own design. In 1908, Toledo, Ohio introduced a signal with "Stop" and "Go" in white on a green background, with red and green lenses lit by kerosene lamps.
The first electric traffic light was developed in 1912 by Lester Wire, a policeman in Salt Lake City, Utah. It was installed in Cleveland, Ohio, on the corner of East 105th Street and Euclid Avenue in 1914. This design was inspired by railroad lights and had red and green lights with a buzzer. In 1917, the first interconnected traffic signal system was installed in Salt Lake City, allowing control of six intersections from a single manual switch.
In 1920, William Potts, a Detroit policeman, invented the first four-way, three-colour traffic light, adding a yellow "caution" light. This was a breakthrough in road safety, allowing for more efficient and organised traffic control. By 1923, Garrett Morgan, an African American inventor, had patented an electric automatic traffic signal with a T-shaped pole, adding an "all-direction stop" to allow safe passage for emergency vehicles and pedestrians.
Traffic lights continued to evolve with the introduction of staggered systems in 1926, allowing early green waves to improve commuting speeds. In 1928, the twelve-light system was invented, with hoods and sand-blasted lenses for better visibility. The 1950s saw the introduction of computerised control, with pressure plates detecting cars at intersections. The 1960s brought adaptive traffic signals that adjusted based on traffic flow, and in the 1990s, countdown timers were introduced to aid pedestrians.
Today, nearly every country uses electric traffic lights, with the exception of Bhutan, which still relies on police to direct traffic. The future of traffic lights may include a new "blue phase" signal, enabling connected vehicles to improve speed and efficiency at intersections.
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The future of traffic lights
The electric automatic traffic light is a vital invention that has played a crucial role in managing road traffic and enhancing road safety worldwide. While the traditional three-colour traffic signal design remains a staple at road intersections, the future of traffic lights is set to evolve with technological advancements. Here's a glimpse into what the coming years may hold for this essential aspect of road infrastructure:
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The Internet of Things (IoT) is expected to play a significant role in the future of traffic lights. With the increasing connectivity of devices and systems, traffic lights will become smarter and more interconnected. Real-time data from sensors, cameras, and other connected devices will enable traffic lights to adjust timing and signalling based on current traffic conditions. This adaptive signal control technology will optimize traffic flow, reduce congestion, and improve overall road efficiency. Additionally, the integration of IoT will allow for better coordination between traffic lights, leading to smoother and faster journeys, particularly during peak hours.
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Another development in the evolution of traffic lights is the integration of machine learning and artificial intelligence (AI). These technologies will enable traffic lights to learn and adapt to traffic patterns, predicting high-traffic periods and adjusting signalling accordingly. AI-powered traffic lights will also be able to detect and respond to emergencies, such as accidents or the passage of emergency vehicles, by giving priority signals to expedite response times. Furthermore, machine learning algorithms can analyze data to identify potential safety hazards and high-risk areas, helping traffic authorities make data-driven decisions to improve road safety.
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As we move towards a more sustainable future, the power sources for traffic lights are also undergoing a transformation. Solar-powered traffic lights are already in use in many places, reducing reliance on traditional power grids. In the coming years, we can expect to see more energy-efficient designs, such as wind-powered or kinetic energy-harvesting traffic lights, particularly in remote or off-grid locations. These alternative power sources will not only reduce operational costs but also ensure that traffic lights remain functional during power outages or in areas with unreliable electricity access.
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The physical design of traffic lights is also set to undergo changes. Traditional bulb-based signals will be largely replaced by longer-lasting and more energy-efficient LED lights. Additionally, to enhance visibility and safety, we may see the incorporation of laser projections or holographic displays. These advanced projection systems could create virtual traffic lights that are more noticeable to drivers and reduce the physical infrastructure required at intersections. Such designs would also be beneficial in adverse weather conditions, improving visibility and reducing the risk of accidents.
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Lastly, the future of traffic lights is closely tied to the development of autonomous vehicles (AVs). As AV technology matures, seamless communication between traffic infrastructure and self-driving cars will become essential. Traffic lights will likely incorporate Vehicle-to-Infrastructure (V2I) communication technology, enabling them to communicate directly with AVs. This two-way communication will allow AVs to receive real-time signal information, and traffic lights will be able to adjust signalling based on the presence and behaviour of autonomous vehicles, further optimizing traffic flow.
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Frequently asked questions
Garrett Morgan invented the first electric automatic traffic light in 1923.
Garrett Morgan's traffic light used a T-shaped pole with three positions: stop, go, and a warning position in between stop and go.
The invention of the first electric automatic traffic light revolutionized traffic control. It was unmanned and cost-effective to operate, allowing it to be installed in various locations.
Yes, Garrett Morgan received Patent No. 1,475,024 on November 20, 1923, for his three-position traffic signal.
Yes, Garrett Morgan sold the patent to General Electric for $40,000.
