Why Are Traffic Lights Red, Yellow and Green?

The idea that red means stop and green means go affects more than just traffic light colors and red light cameras. We have been taught from a young age that red means danger, while green means safety. But why were those particular colors chosen for traffic lights in the first place? For something we have to look at every day, why couldn&#;t they have been prettier colors, like magenta and turquoise? You&#;re about to find out.

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While you&#;re in the mood to learn, here are even more interesting facts and explanations for other little things you&#;ve always wondered about.

When were the first traffic lights created in the United States?

The first traffic lights in the United States were installed because of an increase in travelers on the road in the s. Worried about accidents, towns and cities installed traffic towers to help the flow of cars. Officers manned the towers, using whistles and red, green and yellow lights to indicate to drivers when they should stop and go.

Then, in , William Potts created the first tricolor, four-directional traffic signal. It helped drivers stay safe at intersections. The very first four-directional traffic light was installed at Woodward Avenue and Fort Street in Detroit, Michigan.

But throughout the country, there were still a lot of systems for traffic lights and patterns in place. Since this could end up causing more problems for drivers, the Federal Highway Administration created the &#;Manual on Uniform Traffic Control Devices&#; in . It set uniform standards for all road signs, pavement markings and traffic signals, requiring them to all use red, yellow and green light indicators.

What&#;s the history behind the colors?

It&#;s important to know that before there were traffic lights for cars, there were traffic signals for trains. At first, railroad companies used red to mean stop, white to mean go and green to mean caution.

As you can probably imagine, train conductors ran into a few problems with the color white meaning go&#;bright white could easily be mistaken for stars at night, with train conductors thinking they were all clear when they really weren&#;t. Railway companies eventually moved to the color green for go. And because it&#;s easily distinguishable from the other colors, yellow became the standard for indicating when trains should proceed with caution. It&#;s been that way ever since. On another note, if you&#;ve ever wondered, here is why the lines on the roads are yellow.

When traffic lights were put up, it became standard for them as well&#;except in Japan, where you&#;ll find an entirely different color that signals go.

Why was red chosen for stop?

Red is the color with the longest wavelength; that means that as it travels through air molecules, it gets diffused less than other colors, so it can be seen from a greater distance. For a real-world example, think about how the light turns red as the sun sets. Even though the human eye is most sensitive to a yellow-green highlighter color (hence the shade of high-visibility safety vests), it can see red from further away.

Yellow has a shorter wavelength than red but a longer wavelength than green. This means that red is visible the furthest away, yellow in the middle and green the least distance away&#;a helpful advanced warning for needing to slow or stop. But this could be a coincidence. Red meaning stop originated with train warning lights, and it&#;s not clear whether that was chosen based on wavelength, contrast against green nature or natural association of red with things like blood. It could be a combination of all three! Speaking of colors, read on to find out why this is the world&#;s ugliest color.

Believe it or not, yellow was once used to mean stop, at least as far as signage goes. Back in the s, some stop signs were yellow because it was too hard to see a red sign in a poorly lit area. Eventually, highly reflective materials were developed, and red stop signs were born. Since yellow can be seen well at all times of the day, school zones, some traffic signs and school buses continue to be painted the color. Keep these safe driving tips in the back of your mind whenever you see a yellow light.

Next time you&#;re impatiently waiting at a traffic light, don&#;t get mad; employ these driving etiquette rules and know that traffic lights have certainly come a long way.

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Have you ever wondered why traffic signals are adorned with the familiar red, yellow and green colours? These seemingly simple hues play a critical role in regulating the chaos of our bustling streets, ensuring order, safety and the smooth flow of traffic.

In this month&#;s blog, we embark on a journey through time to explore the intriguing history and psychology behind the colour scheme of traffic signals. Join us as we delve into the significance of each colour and its pivotal role in modern traffic control solutions.

The Colourful Past of Traffic Signals&#; From Directing Railways to Our Roadways

The history of traffic signals dates back to the early days of the railroad industry. Before the introduction of traffic lights for road users, trains had their own system of signals. This system, established in the s, laid the foundation for the familiar colour scheme we see on modern traffic lights.

In the early days of the railroad industry, red was used to signal &#;stop,&#; white meant &#;go,&#; and green was employed to indicate caution. However, this system had its flaws. At night, train conductors mistook the glowing white light for stars, incorrectly believing they had the green light to proceed.

A pivotal moment in the evolution of traffic signals occurred in when a red lens fell out of its holder, leaving the white light exposed. Tragically, this mishap led to a catastrophic train collision, highlighting the need for a more foolproof signalling system.

In response to this incident, railway companies swiftly transitioned to using the colour green to signal &#;go.&#; Green was chosen because it was easily distinguishable from the other colours. Yellow, with its distinctive appearance, then became the standard for indicating when trains must proceed with caution.

How did this system transfer to roadways?

In the streets of London, England, in , a serious problem was brewing. The ever-increasing presence of horse-drawn carriages was causing grave concerns for pedestrians attempting to navigate the perilous road crossings.

This growing issue prompted a visionary railway manager and engineer named John Peake Knight to step forward. Knight, renowned for his expertise in designing signalling systems for British railways, presented an innovative solution to the Metropolitan Police.

Link to FAMA

His idea was a semaphore and light-based system for controlling road traffic. By day, this system employed a police officer wielding a mechanical arm that could be raised or lowered to signal carriages when to halt, with the arm sticking out sideways as a clear indicator. Once the sun set, Knight&#;s system ingeniously harnessed the power of red and green lights to convey the messages of &#;stop&#; and &#;go.&#;

The authorities embraced Knight&#;s proposal, and on December 10th, , the first traffic control system of its kind was implemented at the intersection of Great George and Bridge Street in London, right by the halls of Parliament. The results were promising, and the system functioned smoothly for about a month.

However, fate had other plans. A gas line supplying the lighting began to leak, resulting in a catastrophic incident where an officer operating the signalling arm suffered severe burns. Thus, despite its initial success, the semaphore traffic system was promptly abandoned in England.

Across the Atlantic, in the United States, a similar concern for road safety prevailed. Policemen were deemed the sole authoritative figures capable of directing traffic and in response, traffic towers were erected to facilitate the orderly flow of vehicles. Specially designated officers took their positions in these towers, armed with a system of red, green and yellow lights to guide road users.

The First Tri-Colour Traffic Light

In , a police officer by the name of William Potts introduced a ground-breaking innovation to road safety &#; the first tricolour, four-directional traffic signal. This invention aimed to assist drivers in navigating intersections safely.

Subsequently, several inventors ventured into devising alternative designs for traffic signals. Many of these designs necessitated human intervention, such as pushing buttons or flipping switches to change the signal lights. However, this manual approach proved to be both labour-intensive and expensive.

It wasn&#;t until the late s that automatic traffic signals started to emerge. The initial models relied on a basic system of changing lights at fixed time intervals. However, this simple approach had a drawback&#; it often left vehicles halted at intersections when there were no oncoming cars.

The turning point came with the inventive mind of Charles Adler Jr., who created a signal that responded to the honking of a vehicle. Equipped with a microphone mounted on a pole at the intersection, the system listened for honks and altered the traffic signal lights accordingly. Unfortunately, the local residents and workers were less than thrilled about living near such a noisy system.

Soon, a more discreet and efficient automatic system entered the scene. Henry A. Haugh&#;s design utilized two metal strips to sense pressure. When vehicles passed over these strips, they would press together, triggering a change in the traffic lights and signalling the cars to proceed.

Setting the Standard on Traffic Control Devices

The evolution of traffic control systems has been a fascinating journey, marked by clear innovations. However, a major challenge arose when drivers found themselves navigating through regions with varying traffic control mechanisms. To address this issue and ensure a unified and standardized approach to traffic control, the Federal Highway Administration took a significant step and created the &#;Manual on Uniform Traffic Control Devices&#; in .

These principles set uniform standards for road signs, pavement markings and traffic signals. A pivotal element of this standardization was the requirement for the use of the universally recognized red, yellow, and green traffic light indicators.

Understanding the Colours of Traffic Signals

Traffic lights play a crucial role in regulating traffic flow and ensuring road safety.Each colour displayed by a traffic light holds a distinct meaning, triggering specific reactions from drivers and pedestrians &#; from the red traffic light commanding a complete halt to the green traffic light invoking a sense of permission.  

These colours act as a visual language on the road, guiding our actions and fostering order amidst the bustling chaos of traffic. Let&#;s delve into the reasoning behind the traffic signal light colours:

Why Red for Stop?

Red is the boldest of all the colours, commanding immediate attention and action. Its significance goes beyond its striking appearance, extending to its unique properties in the realm of light and visibility.

With the longest wavelength in the visible spectrum, red is the least likely to be interfered with by other light sources in what is commonly referred to as &#;light scattering&#;. This proves especially valuable when confronted with adverse weather conditions like fog or dust. In such conditions, red traffic lights prevail as they can easily penetrate without becoming diffused, maintaining clarity and visibility over long distances.

As we learned earlier, the origins of using red for signalling &#;stop&#; have intriguing historical roots. Whether it was chosen for its extended wavelength, its contrast against the foliage, its natural association with injury and blood, or a combination of these factors, remains unclear.

Nonetheless, red traffic lights unmistakably convey danger and are intended to prevent specific actions or draw attention to emergencies. This enduring choice of colour ensures instant recognition and serves as a critical element in road safety.

Why Yellow for Caution?

The use of yellow traffic lights to convey caution is rooted in an interesting historical twist. Surprisingly, there was a time when yellow was employed as a signal to &#;stop.&#; This practice dates back to the early s when stop signs, primarily those located in poorly lit areas, were upgraded with the colour yellow to enhance visibility.

However, progress in technology brought about a transformative change in the world of traffic signage. Highly reflective materials emerged, quickly gaining prominence, and rendering the classic reflective stop sign design that we are familiar with today. This technological leap ultimately led to the replacement of the older yellow stop signs, making red the standard colour for these crucial road markers.

Nevertheless, yellow&#;s unique visibility qualities persisted. This is why you&#;ll still find yellow used in certain applications such as school zones, some traffic signs and school buses. While not as attention-grabbing as red, yellow manages to capture the focus of road users and serves as a reminder of the importance of caution and vigilance on the road.

Why Green for Go?

The selection of the colour green to signify &#;go&#; in traffic lights is rich in symbolism, emphasizing safety and a call to positive action. Positioned at the opposite end of the colour spectrum from red, this deliberate contrast serves a vital purpose.

Green, as a colour, has a historical association with safety and affirmation. When a green traffic light shines, it serves as a reassuring sign to drivers that the way is clear, and they can safely proceed. It embodies the concept of progress and moving forward without hindrance, making it a powerful symbol for safe and unobstructed travel on our roads.

Colour Psychology and NAT Traffic Control Solutions

Colour psychology is a crucial element in the effectiveness of our traffic control solutions. Each colour carries its own set of connotations and can significantly impact how drivers and pedestrians perceive and respond to traffic signals. Whether it&#;s the urgency of red, or the safety associations of yellow, understanding these nuances is vital for creating safer roadways.

At North America Traffic, we apply this knowledge to our Portable Traffic Signals and Automated Flagger Assistance Devices to enhance their functionality and ensure the smooth flow of traffic. To learn more about our innovative solutions and how we integrate colour psychology into each traffic signal and flagger device, contact us today.

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