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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 1830s, 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 1914 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 1865, 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.

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 10^th, 1868, 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 1920, 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 1920s 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 1935.

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 1900s 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.