Traffic Signal History

Traffic control devices have a rich history that dates back several centuries. The need for such devices arose as human transportation evolved and the volume of vehicles increased. Here is a brief overview of the history of traffic control devices.

Ancient Times: The earliest known form of traffic control can be traced back to ancient Rome, where stone columns known as "milestones" were placed along the roads to provide distance measurements and direction guidance.

19th Century: As horse-drawn carriages became popular in the 19th century, cities began implementing rudimentary traffic control measures. Police officers or "traffic constables" were assigned to direct traffic manually using hand signals and whistles.

Early Traffic Signals: The first mechanized traffic control device was the semaphore, developed in the late 19th century. Semaphores were large arms or flags mounted on a pole, which were manually operated to indicate "stop" or "go" to traffic. They were used in various cities, including London and Paris.

Electric Traffic Signals: The first electric traffic signal was introduced in 1912 in Salt Lake City, Utah, USA. It consisted of two colors, red and green, and was manually operated. However, the lack of automated timing made it less efficient.

Automated Traffic Signals: In 1920, a police officer named William Potts invented the first automated traffic signal in Detroit, Michigan, USA. Potts' invention used a four-way, three-color system with red, amber, and green lights, which were timed to change automatically. This innovation significantly improved traffic flow.

Road Signs: The use of road signs to convey traffic rules and information became more standardized in the early 20th century. The first international road sign system was developed in 1909 by the International Road Congress, later replaced by the Vienna Convention on Road Signs and Signals in 1968.

Reflective Materials: Reflective materials were introduced to enhance the visibility of traffic control devices. In the 1930s, the first reflective road signs were made using glass beads. In the 1950s, the development of reflective paint and tape further improved the visibility of signs, making them more effective at night.

Modern Innovations: Over time, traffic control devices have continued to evolve. Modern innovations include the introduction of traffic lights with advanced features such as pedestrian signals, countdown timers, and sensors that adjust timing based on traffic conditions. Electronic message signs and variable speed limit signs are also used to provide real-time information to drivers.

Intelligent Transportation Systems: In recent years, technology has played a significant role in traffic control. Intelligent Transportation Systems (ITS) use advanced sensors, cameras, and communication networks to monitor and manage traffic flow more efficiently. This includes adaptive traffic signal systems that adjust timing based on real-time traffic conditions and interconnected traffic management systems.

Traffic control devices have come a long way, adapting to the changing needs of transportation and advancements in technology. They play a crucial role in promoting safe and efficient movement of vehicles, pedestrians, and cyclists on roads.

SIGNAL HISTORY TIMELINE

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 work better with a signal system to keep traffic moving while human drivers could follow them during the blue phase.

Citation:https://magazine.wsu.edu/web-extra/traffic-signals-a-brief-history/

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