But why, why, why
Was the traffic light green?
And that's why, that's why, that's why
That he was in love with life.

© Zinoviev N.N.

A traffic light (from Russian light and Greek φορός - “bearing”) is an optical device that carries light information. We all know from childhood that traffic lights are red, yellow and green, and sometimes blue and moonlight white. Red light prohibits movement, yellow is usually a warning signal that attracts attention, and green, blue and white signals allow movement. Why are these colors used in traffic lights to regulate traffic around the world?

In 1868, English inventor John Peak Knight proposed using a device similar to a railway semaphore to regulate traffic in London near the British Parliament. During the day, the “stop” and “move with caution” signals were indicated by arrows that could take different positions, and in the evening, a rotating gas lamp was used for the same purpose, with the help of which red and green signals were given, respectively.

At the beginning of the 20th century, the first electric traffic lights began to be installed in America, first with two signals - red and green, and then a yellow signal was added to them. In the USSR, the first traffic light was installed in 1930, but then blue was used instead of the usual green signal. In addition, until 1959, when the USSR joined the International Convention on Road Traffic and the Protocol on Road Signs and Signals, the colors of the traffic lights were reversed - the top was green and the bottom red.

Of course, these colors of traffic lights were not chosen by chance. The choice was influenced by several factors, one of which is the psychology of human perception of different colors. Red is traditionally considered a warning of danger, while green, on the contrary, is the color of life and tranquility.

But one of the main reasons for this choice of colors is the dependence of the degree of scattering of light on its wavelength. According to Rayleigh's law, the degree of light scattering is inversely proportional to the fourth power of the wavelength. This means that short-wave radiation - blue and violet - is scattered more strongly. And red, as a color with a longer wavelength, will therefore be visible from a greater distance. Obviously, the most important is the warning of danger and the prevention of accidents, so the stop signal is indicated in red. For the same reason (the degree of scattering), the blue signal, as having a shorter wavelength and scattering more strongly, gave way to green.

Surprisingly, in Japan, a green traffic light is called blue. The fact is that when the first street lights appeared in Japan, the signals in them were red, yellow and blue. The blue lenses of traffic lights were eventually replaced with green ones, but the custom of calling the traffic signal “blue” remained. The peculiarity of the Japanese language is that, therefore, the Japanese call many green objects blue.

Traffic lights are a common thing these days, and you, like all other drivers, are required to follow the rules: stop at a red light, prepare for a yellow one, and pass on a green one.

There is no doubt that traffic lights should be in densely populated cities. Be that as it may, this the only way control traffic when there is no police nearby.

Riding every day from home to office, we can’t even imagine a road without at least one traffic light, but there were times when traffic lights didn’t exist at all. Of course, the roads were relatively free...

So, as already mentioned, when you get behind the wheel, you must adhere to certain rules. Traffic lights are the same all over the world and consist of three different colors that have their own specific purpose. But how did it happen that the traffic light is exactly red, yellow and green? Why isn't it purple, brown and grey? There are several suggestions on this topic, but first a little history.

It's no secret that the automotive industry pioneered many important things that are still used around the world today, but in turn, it had to borrow something from other industries. A good example is a traffic light.

The first traffic light saw the light in 1868 in London. It was used exclusively to manage rail traffic at the intersection of George and Bridge Streets. The design was quite simple, but performed its function very well. It was made up of two vertical switches that could change to a horizontal position to indicate to trains that they should stop. At a 45-degree angle, the system meant what yellow light does today: attention.

And now the most interesting thing: since the signaling device was completely invisible at night, the engineers decided to install primitive lights on it that would display the "stop" and "attention" modes. What was their color choice? Red for "stop" and green for "attention".

You are probably wondering how the green light became a signal for "attention"? Well, no one knows for sure, but that all changed a few years later when traffic lights made their way into the automotive industry.

Very important point happened in 1912 in the USA (where else?) thanks to Lester Farnsworth Wire, in charge of traffic in the Salt Lake City Police Department. The first manually operated traffic light had only two colors: red and green. Although at that time there were practically no cars on the roads and the rules of the road were not yet prescribed, the drivers were surprised by the new invention, so the presence of a policeman was necessary to force them to obey the device.

The first three-color traffic lights appeared again on railway, however the trio was slightly different: red for "stop", green for "attention", white for "free". While the first two have a more or less obvious meaning, the white signal has become a headache for the authorities. Similar lights, whether they were stars or street lights, misled the drivers, leading to fatal collisions.

Why are traffic lights red, yellow and green

The color red is most often associated with blood and thus was chosen as a prohibitory signal. Symbolizing a dangerous situation leading to serious consequences, red has always been chosen as the color that encourages vehicles stop and avoid accidents.

As for green, color symbolism also became the reason for its use. As with red, green is the source of human emotion. It is associated with something relaxing (for example, nature) that will not have a powerful negative impact on drivers. In addition, the green color is easy to recognize at night.

The choice of yellow was surprising. Many believe that it symbolizes the sun, which is also considered a relaxing and at the same time attention-grabbing element.

Traffic lights have evolved over the years, especially in terms of their effectiveness for colorblind people. Commissioners in many countries have dealt with this issue in different ways, whether it was traffic lights with double red light or sections of different shapes. One way or another, the classic design had to be slightly changed.

Since color blindness is one of the most common forms of visual impairment, these days a little orange is mixed with red - in this case, color blind people are able to notice a brake light. For the same purpose, a shade of blue is added to green.

Why are traffic lights red, yellow and green

05.08.2015 03.12.2015 by [email protected]

As you know, you can only cross the road in the places provided for this and only at the green traffic light. But traffic lights appeared at our intersections not so long ago, before traffic controllers were involved in coordinating traffic. Who owns the palm? Today, on the Birthday of the Traffic Light, we will deal with this issue.

1. Inventors of the traffic light

The first person to think of installing a traffic light at a crossroads to regulate traffic was John Peak Knight, a Londoner and specialist in railway semaphores. The first traffic light designed by him was installed in the British capital on December 10, 1868 near the Houses of Parliament.

Switching signals was carried out manually using two semaphore arrows. In a horizontal position, they signaled "stop", and lowered at an angle of 45 ° - movement with caution. So that at night it was possible to identify the signal given by the arrows, a rotating gas lamp was used, which shone red or green.

In 1910, Ernst Sirrin of Chicago developed and patented the world's first automatic traffic light switching system. His traffic lights had two inscriptions Stop and Proceed without illumination.

Just a couple of years later, in 1912, a resident of Salt Lake City, Utah, whose name was Lester Wire, created the world's first electric traffic light, with two round signal lights of red and Green colour. For unknown reasons, Vayr did not patent his invention.

The next name in traffic light history is James Hogue. On August 5, 1914, the American Traffic Light Company installed four electric traffic lights designed by Hog at the intersection of 105th Street and Euclid Avenue in Cleveland.

Traffic lights were equipped with two light signals - red and green, and when switching they gave a sound signal. The whole system was controlled by a policeman who sat in a specially equipped glass box at the crossroads.

Six years later - in 1920 - traffic lights were installed in Detroit and New York, on which a yellow signal appeared. The people who developed them did not know each other: William Potts from Detroit and John F. Harris from New York.

Similar traffic lights were installed in 1922 in Paris at the intersection of Rivoli Street and Sevastopol Boulevard, as well as in Hamburg at Stephansplatz Square. In 1927, the same traffic lights appeared in Wolverhampton, England.

Often, the American inventor Garrett Morgan is often mentioned as the first inventor, who in 1923 received a patent for a traffic light of an original design. The first traffic lights countdown appeared in France in 1998.

Concerning Soviet Union, the first traffic lights were installed here in the early 1930s. First, the traffic light appeared at the intersection of avenues on October 25 and the Volodarsky city of Leningrad (modern Nevsky and Liteiny avenues in St. Petersburg) on ​​January 15, 1930. In Moscow, the first traffic light began work on December 30 of the same year at the corner of Petrovka and Kuznetsky Most.

2. Types of traffic lights

The most widely used street and road traffic lights. Among them, automobile and traffic lights for pedestrians stand out - these varieties are most often found on the roads of the whole world.

Automobile traffic lights. As a rule, there are traffic lights with round signals of three generally accepted colors: red, yellow and green. The order of colors is strictly regulated. If the signals are arranged vertically, then red is always on top, and green is on the bottom. If the traffic light is horizontal, then the red signal will be located on the left, and the green one on the right. Additional sections with arrows are often hung on car traffic lights.

A yellow signal almost everywhere means this: it is allowed to pass the stop line, but it is necessary to slow down when entering a section protected by a traffic light, ready for the traffic light to switch to red. This signal can also be orange.

Traffic lights for pedestrians installed in the immediate vicinity of the established transitions. There are usually only two signals on them - forbidding and allowing. Appearance they may differ. The most common signals are in the form of a silhouette of a person - standing or walking.

In some countries, in the USA for example, the red signal is made in the form of a raised palm. Sometimes, instead of men and palms, the inscriptions "Go" and "Do not go" are used. In Oslo, two standing red human figures are used as a traffic signal forbidding pedestrians.

Why such difficulties? This is done for the convenience of people with poor eyesight, as well as for those who have difficulty with color discrimination (color blindness). In addition, traffic lights different countries equipped with an audible signal.

3. Design

What are traffic lights made of? There are several possible designs of traffic lights. The first option is traffic lights with incandescent or halogen lamps. Their design includes:

• Lamp
• Reflector
• light filter
• Fresnel lens
• Visor.

• Matrix of LEDs
• Anti-vandal glass
• Visor.

In Russia there is a monument to a traffic light.

It was installed in Novosibirsk in 2006.

The order of alternation of traffic lights corresponds to the international Convention on Road Signs and Signals. Traffic lights alternate in the following sequence: red - red with yellow - green - yellow - red. Alternation of signals red - green - yellow - red or red - yellow - green - yellow is allowed.

A red solid signal prohibits movement across the entire width of the carriageway. Varieties of the red signal:

A contour black arrow on a red background of a round shape prohibits movement in the direction of the arrow;

An oblique red cross prohibits movement along the lane over which it is installed;

The red silhouette of a man forbids pedestrian traffic;

Red flashing prohibits entry to a railway crossing, bridge, pier, etc.

A yellow solid signal obliges all drivers to stop before the stop line, with the exception of those who could not stop before the intersection.

Yellow connected to red warns that the green signal is on.

A yellow flashing signal warns of the presence of an intersection and does not prohibit movement.

A green steady signal in the absence of any additional sections of the traffic light allows movement along the entire width of the carriageway in all directions.

Varieties of green signal:

A black arrow on a green background of a square, round shape, as well as a green arrow on a black background of a round shape - permission to move in the direction of the arrow;

A green arrow on a black background of a square shape, pointing down, allows movement in the lane over which it is installed;

A signal in the form of a green silhouette of a person allows pedestrian traffic;

The green arrow of the additional section of the traffic light allows movement in the direction of the arrow, regardless of the signal of the main traffic light;

A flashing green signal warns of the end of the enable signal.

Permission for the movement of public transport depends on the combination of the included signals of the upper and lower rows of a special traffic light. Turning on the lower signals movement is prohibited in all directions.

Studies have shown that there is a so-called critical section before the intersection and, being within this section, the driver cannot stop in time in front of the stop line when changing the permissive signal to prohibitive.

The critical section is defined as the distance from the stop lines to the point where 10% of drivers cannot stop. The length of the critical section depends on the speed of movement. So, at a speed of 50 km/h, the length of this section is 43 m and the travel time for this section is 3.1 s; at a speed of 60 km - the length of the section is 58 m and the travel time is 3.5 s; at a speed of 80 km - the length of the section is 91 m and the travel time is 4.1 s.

Hence, the travel time of the critical section at different speeds varies within 3-4 s. This prompted us to use a flashing green signal as a warning and take the flashing time equal to the time of passage of the critical section. In order not to reduce the throughput of the intersection. with a permission signal, a green flashing signal is introduced in part at the expense of the duration of the yellow, which will allow you to safely pass the intersection.

Types of traffic lights. Traffic lights are classified according to their functional purpose - transport and pedestrian; by design - one, two-section, three-section and three-section with additional sections; according to the role performed in the process of motion control - the main ones, backups and repeaters.

The main two groups of traffic lights: transport and pedestrian, which in turn are divided into types. There are 8 types of traffic lights and 2 types of pedestrian ones. The first traffic light number means the group, the second number - the traffic light type.

traffic lights Type 1 have three round signals with a diameter of 200 or 300 mm, arranged vertically or horizontally.

The first type is used with additional sections, in which arrows indicate the direction of movement (arrows on a black background). Traffic lights of this type are used to regulate all directions of traffic at intersections. Their use is allowed at railway crossings, intersections with tram and trolleybus lines, in narrowings of the carriageway, etc.

Traffic lights 2 types. On the lenses of the traffic light, the contours of the arrows are applied. indicating permitted or prohibited movement. In this case, the green signal (arrow) is applied on a black background. Type 2 traffic lights are used to regulate traffic in certain directions (indications on the arrow lens).

Traffic lights type 3. They are used as repeaters and in conjunction with type 1 traffic lights.

They are installed under the main traffic light at a height of 1.5-2 m from the roadway. The diameter of the signals is 100 mm. If the main one has an additional section, then the repeater will be equipped with an additional section. Traffic lights of this type can be installed to control cycling.

Traffic lights type 4. They are used to control entrances to separate traffic lanes, with reverse traffic.

They are installed above each lane at its beginning. They have a horizontal arrangement of signals; on the left - in the form of an oblique red cross, on the right - in the form of a green arrow pointing downwards. Both signals are executed on a black rectangular background. Overall dimensions 450 x 500 mm.

These traffic lights can be used together with type 1 traffic lights if the reverse traffic is not organized across the entire width of the carriageway. In this case, the type 1 traffic light does not apply to lanes with reverse traffic. This lane may be delimited by a double broken line 1.9 when the type 4 traffic light is turned off.

Traffic light type 5. Has 4 signals of pale moon color of a round form with a diameter of 100 mm. This traffic light is used in cases of conflict-free regulation of the movement of trams, shuttle buses, trolleybuses moving along a specially allocated lane. In the scheme of organizing traffic at the intersection, a conflict-free passage is provided, i.e., the indicated types together with the general flow, therefore, there is no need to use this type at the intersection.

Traffic light type 6. It has two (or one) round red signals with a diameter of 200 or 300 mm, located horizontally and operating in the alternate flashing mode. When the signals are off, movement is allowed. They are installed in front of railway crossings, drawbridges, berths, ferry crossings, in places where special vehicles enter the road.

Traffic light type 7. Has one signal yellow color, constantly working in flashing mode. It is used at unregulated intersections of increased danger.

Type 8 traffic lights. They have two vertical signals of red and green colors of round shape W 200 or W 300 mm. They are used for temporary narrowing of the carriageway, when alternate traffic is organized along one lane. They are also used to control low-intensity traffic in the internal territories of garages, enterprises and organizations where a speed limit has been introduced.

Pedestrians have two vertically arranged signals of a round or square shape with a circle diameter or a square side of 200 mm or 300 mm. All pedestrian crossings at the intersection controlled by traffic lights are equipped.

Traffic lights with a large size are installed on the main streets, squares, on roads with the speed of T.S. 60 km/h

Traffic light design. The traffic light consists of separate sections (Fig. 1) and each section is designed for a specific signal. Depending on the type of traffic light, the sections have different shape, your symbols, light source, etc. Common to all sections is the presence of an optical device placed in a separate housing.

Figure 15 - Traffic light device

The sections are interconnected by threaded hollow bushings 1, through which the supply wires are passed. The section consists of a body 8, a sun visor 4 and a cover 6. They are made of sheet steel or plastic. An optical device is mounted in the cover, which consists of a reflector 7, a colored diffuser lens 3 and a movable glass 10 with an electric lamp. When the glass is moved, the filament of the lamp is set at the focus of the reflector. To connect the current supply at the bottom of the section there is a block 9.

Light source.

As a light source, incandescent lamps are used, both for general and special purposes. So, gas-light tubes or emitting diodes are used as a light source. The main disadvantage of an incandescent lamp - for general use - is the large length of the filament, which is difficult to focus, low vibration resistance of the lamps, and also have a short service life (500-800 hours):

It has been proven that the thread burnout occurs mainly due to inhomogeneity in wire diameter, helix pitch, electrical resistance and evaporation rate.

In some traffic light designs, halogen lamps are used. At small sizes, they have an increased specific light output and a compact filament, and these lamps focus well. However, these lamps were not widely used due to their high cost.

Two simultaneously working lamps can be used in one section, but this requires the installation of a special reflector and a bifocal lens. Such a solution is associated with a complication of the design and an increase in cost.

Abroad, a curved gas-light tube has found application as a light source. The tubes contain a filler of red, yellow or green colors, which eliminates the need for a colored lens. For the glow of the tubes, a voltage of over 2000 V is required, so a transformer is required. They have a long service life, but in terms of signal strength they are 5-6 times inferior to modern traffic lights with incandescent lamps.

Traffic light lenses.

IN last years In our country and abroad, plastic lenses are widely used. They have advantages over glass ones in ease of manufacture, higher strength under impact and vibration loads, as well as less weight (about 3 times). These lenses are usually made from polycarbonate.

Diffuser lenses are designed to redistribute the luminous flux into space. To do this, a patterned, rhombic, prismatic or drop-shaped pattern is formed on their inner side. For modern lenses, this angle is in the range of 5-15°, which ensures normal visibility of the signal on multi-lane roads (100 m).

Reflector.

The reflector is characterized by two main internal surfaces: paraboloid, providing a concentration of the light flux, and conical (or cylindrical), designed to increase the depth of the reflector and thereby reduce lens dye burnout.

With a short focal length, there is a danger of a false traffic signal (phantom effect), when the beam from an extraneous light source, hitting the reflector, returns to the observer again.

In the designs of modern reflectors, the focal plane AA is brought as close as possible to the plane of the light aperture, behind which the non-working conical surface begins.

As a rule, the condition is met:

(13)

where: is the diameter of the light aperture of the reflector, mm.

Reflectors are made of steel, aluminum alloys or plastics with subsequent processing of the inner surface. Plastic reflectors with a working surface obtained by vacuum deposition are widely used.

Anti-phantom devices.

An anti-phantom device in a traffic light is a sun visor, but at a low position of the sun (for example, east-west, west-east), all traffic lights may glow.

There are several methods to eliminate the phantom effect, but they require a change in the design of the reflector or traffic light lens.

The reflector with the so-called anti-phantom cross consists of mutually perpendicular segmented plates with slots for the location of a halogen lamp (Fig. 1).

A beam of light falling from an external light source onto the reflector is deflected and absorbed by the surface of the plates. Another solution is carried out by installing a special anti-phantom lens in front of the light filter 1, consisting of two parts 2, 3, each of which has a sawtooth profile (Fig. 2). A ray of the sun, falling on an inclined surface, is thrown onto a horizontal blackened step and absorbed by it.

Rice. 16 - Anti-Phantom Cross

Fig. 17 - Lens that absorbs the sun's rays

There was a time when you cross the street big city it was not easy at all. People stood on the sidewalk for a long time and waited for the end of the endless stream of horse-drawn carriages. The most impatient ran across the street, risking getting under the hooves of horses or cart wheels.

What can we say about our days, when the flow of cars rushes in several rows! How can pedestrians cross the street? But there are still cars that move in the transverse direction, and they also need to clear the road. To help road users - both pedestrians and drivers - comes traffic light. Translated from Greek, traffic light means “bearer of light”. It regulates traffic with the help of light signals. Most traffic lights use three colors: red, yellow and green.

Why were these traffic light colors chosen?

Red is the color of danger. It is clearly visible both during the day and at night, and in rain and fog. It is no coincidence that fire engines of all countries are painted red. They warn other road users of the danger and demand to give way to them. Here is a red traffic light forbidding traffic. It's like he's saying, "Stop! The path is closed!

Green the color is sharply different from red; they cannot be confused. Therefore, the green signal of the traffic light, unlike the red one, does not prohibit, but allows movement. He seems to say: “The way is open! Boldly forward!

Between the red and green "eyes" of the traffic light, another one was placed - yellow. He urges drivers and pedestrians to be careful, as if telling them: “Attention! Soon traffic will be either allowed or prohibited.

So traffic lights with three sections are installed in cities, in which either a red, or a yellow, or a green signal is lit. They are called three-piece. Sometimes at traffic lights, in addition to the three main color sections, additional green arrows are installed. They indicate the direction in which movement is allowed.

What other traffic lights are there?

Along with three-section traffic lights, there are also special traffic lights for pedestrians. They use only two light signals - red and green. They depict pedestrians. The red man is standing, and the green one is walking. It’s immediately clear to any pedestrian: if a red pedestrian is lit, you can’t go across the road, you have to stand. But if a green pedestrian is lit, you can cross the street.

Most often, such pedestrian traffic lights are installed in places where there is a large flow of cars and it is difficult for pedestrians to cross the road.

Remember this rhyme about traffic lights

If the red light is on -

So your path is closed!

If the yellow light is on -

"Get ready!" - speaks.

And the green light is on

The way forward is open to you!