Traffic Light History and Future
"Red means stop, green means go"—this is a universal traffic law around the world. However, few people know that in the past, green meant go, red meant stop, and yellow meant slow down. Let's explore the little-known history of traffic lights in the article below.
The Birth of the Traffic Light
The current traffic light color scheme originated in the railway industry in the 1830s. At that time, railway companies developed a signal light system to inform train operators when to stop or proceed. The colors represented various actions. Red was chosen to indicate stop, white to indicate proceed, and green to indicate caution.
Image of modern railway signal tower
The reason why red, the color of blood, has been a signal of danger since ancient times. Some historians believe that Roman legions used red flags as symbols of the god of war in battles over 2,000 years ago. It is clear that red is ideal for indicating a stop sign because it is very visually stimulating to humans. However, there were many problems with using white to indicate permission to proceed.
For example, in a 1914 accident, the red filter fell off, revealing the white bulb inside. The lamp operator thought the lamp was working normally, while the train driver saw white and thought he could proceed. As a result, the train crashed into a wagon ahead. In light of this, the railway industry decided to change green to "go" and chose yellow to indicate caution. The railroads believed that the three colors red, yellow, and green were completely different and could be easily distinguished by the naked eye.
How did the signaling system get from the railroad to the road?
In London, England in 1865, there was growing public concern about the increasing number of horse-drawn carriages and the danger they posed to pedestrians crossing the street. At that time, a railway engineer and manager named John Peake Knight, who played an important role in the design of the railway system in England, went to the London Police Department and proposed the idea of using semaphore signals on the railroad. to equip normal roads.
Traffic light proposed by John Peake Knight in 1868
Semaphore signal.
According to John's idea, the traffic light will have one or more arms that can be raised vertically and lowered horizontally to block the road. During the day, police officers would operate them to lift and lower them to tell horse-drawn carriages when to stop and pull over. At night, the pole is equipped with red and green to tell drivers when to go or stop. This event marked the transition of traffic signals from railroads to ordinary roads.
Shortly after, John's proposal was quickly accepted, and on December 10, 1868, the first lamppost was installed at the intersection of Great George and Bridge Street in London. And the system worked very well... until a few months later: one of the gas pipes that supplied the light bulb to the gas lamp leaked. Unfortunately, the police officer standing nearby to operate the branches of the lamppost did not notice the gas leak. As a result, the bulb exploded and the police officer was burned. So despite its initial success, the traffic light was immediately recalled in England.
Development of traffic signals in the United States
In the other side of the ocean in the 1910s and 1920s, police officers in the United States also used a tall tower to have a better view of traffic conditions. During this time, police officers could use green and red lights from the railroad industry to signal to vehicles when to go or stop. Another method used was for the police officer to wave his arm to direct traffic.
In 1920 in Detroit, Michigan, a police officer named William L. Potts invented a four-sided, three-color traffic signal model that used all three colors red, yellow, and green to control traffic at intersections. This event marked the fact that the city of Detroit became the first in the world to use the three-color red, yellow and green traffic light, which is still widely used today. Afterwards, many inventors continued to redesign different models of traffic lights, some still using the three colors red, yellow and green, others choosing other colors. At that time, traffic lights required a person to operate the circuit breaker, press a button, etc., to change the color of the light. And, of course, the cost to implement and operate traffic lights with this method was quite expensive.
Four-sided, three-color traffic light model proposed by William L. Potts
In the late 1920s, some automatic traffic lights were invented. The first model used a simple method of changing the color of the light after a certain period of time. However, the disadvantage of this method is that it causes some vehicles to stop while no vehicle crosses the intersection. At that time, an inventor named Charles Adler Jr. proposed an idea to overcome this situation.
Accordingly, Alder invented a traffic light model that could detect the sound of a car horn. A microphone is installed at the intersection of 2 roads. When a vehicle stops, all the driver has to do is honk the horn to change the traffic light. To keep drivers from constantly honking the horn causing the color of the light to change too quickly, Alder also规定that once the light has changed color, it will only change color again after 10 seconds has passed. He believes that this period of time will allow at least 1 car to cross the road safely. And of course, this system has caused much annoyance to pedestrians and households near the intersection due to the constant sound of horns honking.
Image of the inside of a traffic signal control center in the 1970s
At the same time, inventor Henry A. Haugh proposed a new traffic light system to overcome the previous drawbacks. Haugh's system uses 2 metal strips to detect when a car is driving up. When a vehicle passes and makes the 2 metal strips touch each other, the light will soon change color to allow the vehicle to continue moving forward. However, Haugh's model revealed a flaw, in some cases where the vehicle was not driving to the right point, the light switching system would not operate.
It wasn't until the 1950s that the development of computers marked a significant improvement in the way traffic lights change color. Traffic lights were operating more accurately and faster. In 1952, 120 traffic lights in the city of Denver were controlled by a computer. Then in 1967, the cities of Toronto and Ontario officially deployed a dedicated computer system to control traffic light signals. Soon after, the computer system was able to control traffic signals in 159 cities across the United States via telephone lines. At the same time, the controller can also quickly adjust the timing of the green and red lights using the computer.
Over time, traffic control with traffic signals has become more sophisticated thanks to the development of technology and the support of computers. While the methods may differ, today, green, red, and yellow are still the three main colors used for traffic signals in most countries around the world.
The future of traffic lights: adding a fourth color, integrating AI?
Modern traffic lights have 3 colors. (Photo: Shutterstock).
Different colors, sometimes flashing, work best for the human brain, while self-driving cars work better with a single light.
Professor Ali Hajbabaie of North Carolina State University (NCSU) is leading a team designing a traffic system for self-driving cars.
Therefore, it is very possible that white will be the fourth color added to traffic lights when self-driving cars become more popular. White light will be interpreted by self-driving cars as a "continue unless otherwise instructed" instruction.
Although there are many different types of traffic signal technologies, most traffic light systems fall into two categories: signals that operate on a fixed schedule; and signals that can adjust timing based on traffic volume.
Professor Henry Liu of the University of Michigan (USA), has developed another approach to addressing traffic congestion with artificial intelligence (AI). Liu and his team are testing using real-time speed and location data from cars equipped with Global Positioning Systems (GPS) to adjust traffic lights. They are conducting the experiment in the Detroit suburb of Birmingham, Michigan.
Professor Liu explains that no information from cameras or sensors is needed to adjust the flow of traffic, meaning the traffic light can only receive information from vehicles to adjust without any intervention.
Summary
Throughout history, traffic lights have played a vital role in improving road safety and traffic management. From its origins in the railway industry to the modern-day use of AI, the evolution of traffic lights is a testament to human ingenuity and the continuous quest for better ways to manage traffic.