A history of colors in road signs and traffic lights (2023)

Stop signs are red. Warning signs are yellow. Construction signs are orange. These colors and what they represent on the street have been embedded in our daily lives since we were children. Seeing these colors so often, it's natural to overlook the different methodology that determines why road signs and traffic signals are the colors they are, and the factors that go into decisions to add specific colors to specific shapes to improve the guarantee of road safety.

In general, colors are divided into three groups: warm colors (red, orange, yellow), cool colors (blue, green, purple), and neutral colors (black, white, brown). Warm colors are typically used in graphic design to create strong emotion. Therefore, the vast majority of road signs follow these guidelines.

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If a sign directly tells you to do (or not do) something, it's probably red. For example, "Stop", "Give Way" and "Do Not Enter" signs are all red, and the most important information is communicated on the road through the use of all-red signs or white signs with red text.

Red signs indicate the most important road traffic information. (onRoadTrafficSigns.com).

Orange y Gelb

Similarly, warm colors are used to notify motorists of temporary and permanent hazards. Temporary warnings, usually due to construction, have always used the color orange with black text, while permanent warnings use background text on a yellow background for maximum legibility and visibility. In the past, the most important messages were displayed on yellow banners for maximum visibility day and night. The Manual on Uniform Traffic Control Devices (MUTCD) reports that orange marking was not used until 1964 in response to a further proliferation of highway construction combined with the introduction of reflective aluminum materials for increased visibility. To this day, orange is the standard color for construction sites.

Yellow signs like this indicate a permanent danger, e.g. B. Areas with many pedestrians (viaRoadTrafficSigns.com).

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Orange signs, like this construction site sign, indicate more short-lived hazards. (onRoadTrafficSigns.com).

Verde,Azul y braun

Less important information (that is, information that does not directly influence the driver's actions) is usually placed on signs with neutral or cool colors. This color scheme is used on purpose so as not to draw attention to the driver. The universally recognizable green color on motorway exits and signs indicates information that depends purely on the will of the driver. Blue signage indicates rest stops and restaurants, and brown indicates a place for outdoor recreation. These colors are naturally non-disturbing earth tones, meant not to annoy or advise, but to inform.

A history of colors in road signs and traffic lights (6)

A history of colors in road signs and traffic lights (7)

Red and green signs, such as rest area and exit markers, have cooler colors to avoid distracting the driver.

Negro y Blanco

The main focus of a black and white sign is clarity. Most black and white signs are warning, providing motorists with information that affects their speed and alerting them to potential hazards ahead. Many information signs simply feature black text on a white background to inform drivers clearly without distraction. Speed ​​limit signs, traffic regulations, one-way traffic signs, and level crossing signs are all black and white, with no color to encourage an informative aesthetic.

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Black and white signs like B. These stop, speed limit, and railroad signs are not colored to denote a more informative aesthetic (via RoadTrafficSigns.com).

Color drawing of the past: history and modifications.

A history of colors in road signs and traffic lights (11)

A history of colors in road signs and traffic lights (12)

Yellow stop sign and red stop sign.

Although sign color may seem self-evident, it has never been stagnant: the development of highway signage in the United States has included a large series of updates and modifications. For example, stop signs were not always red. After being first introduced in Detroit, Michigan in 1915, a wide variety of stop sign colors were used across the country. In the late 1920s the color was standardized as yellow; remember that before reflective aluminum was used for traffic signs, this was a particularly poor choice for nighttime hours.

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These 1950s Micro-Flex Co. Inc. signs advertise yellow stop signs with reflective aluminum beads along the lettering of the sign and the later reflective red aluminum stop sign in use today.

The stop sign was certainly not the only traffic sign to change from yellow to red following the adoption of reflective aluminum in traffic signs. Before the 1960s, yield signs were also yellow. While retaining the triangular outline, the original yield sign used yellow to maximize visibility. Today, the yield sign with its characteristic shape, thick red border, and red lettering is immediately communicable and universal.

A history of colors in road signs and traffic lights (15)

With the provision of reflective aluminum, the yield sign changed from yellow to red.

The parking signs did not also change from yellow to red, but they also changed their shape from circular to rectangular. This change comes as a result of the move toward rectangular signs to reduce material waste; the only notable exceptions are yield and stop signs, of course.

A history of colors in road signs and traffic lights (18)

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Parking signs have not evolved from yellow to red and have changed their shape from circular to rectangular to save materials.

Below is an excerpt from the 1935 Manual on Uniform Traffic Control Devices (MUTCD) which lists the standardized specifications for traffic signs in the United States. During this period, orange did not become part of the road sign vernacular, simply because most road works at the time involved building new roads and not maintaining old ones.

HavingoctagonGelbblack or red
the park
train aheadKreisGelbNegro
Railroad crossingKreuzbockBlancoNegro
route marking
auxiliary charactersHorizontalBlancoNegro
rest stationcloverVerdeBlanco


The color of traffic lights also has a living and important history. The red and green stop-and-go colors were derived from early train signals. In the 19th century, trains used gas lamps that glowed red and green to indicate whether the trains should hold speed or stop. Various modifications of this technique were used on the road. One such change was introduced in the early 20th century when a buzzer was used to indicate when the light would change from green to red and vice versa. In New York City, the yellow light appeared to indicate northbound and southbound traffic movement, while the green light meant traffic was moving east and west. This system was not well received and caused a lot of confusion, which led to the appearance of the standardized traffic light: green to go, red to stop, and yellow to slow down.

The traffic light in its current form
Features the familiar red and green lights
(Signed byRoadTrafficSigns.com).

The red light is placed above each traffic light to allow better visibility of a potential stop: when the car goes up a hill, it knows sooner to stop and more effectively reduces danger. A predominantly Irish town in upstate New York, Tipperary Hill, objected to the placement of "British" red over "Irish" green, with local Irish immigrant youth throwing rocks at the town's red traffic light on the first stop. This became such a widespread problem that the city implemented a "green on red" traffic light, which is still in use today, instead of the traditional, standardized version.

Irish residents of Tipperary Hill
keep your pride with the city
Green traffic light on red.

Despite this small protest, the current semaphore system went mainstream on April 27, 1925, and remained free from criticism for nearly a century. Interestingly, traffic light colors match traffic signaling methods: red represents immediate action, yellow caution, and green continuous driving. This overlay is integrated into road marking methods, using warm, cool and neutral colors organically to keep motorists informed in the most efficient and safe way.

The use of color in traffic signals is a constantly evolving entity. With the development of new materials and their improvements in visibility and durability, it is not unlikely that a new systematization of the color coding of traffic signs will take place in the future.


1. The History Behind: Traffic Lights
(Mr. Pharaoh)
2. Traffic Signs and Rules For Kids | Road Safety For Children | Roving Genius
(Roving Genius)
3. The Origin of Red-Yellow-Green Color in Traffic Lights
(HOTs Education)
4. How do engineers make ROAD SIGNS look the same?
(Road Guy Rob)
5. The History of Traffic Signals
(ITS Now)
6. How do stop lights "see" your car (to turn green)?
(Road Guy Rob)
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