The idea of installing traffic lights at street intersections to regulate traffic belongs to Londoner John Peak Knight. By profession, he was a specialist in railway semaphores.
A few historical facts
The first of the traffic lights was designed and installed on a London street in 1868. The signals in it were manually switched by two arrows. Their horizontal position indicated "stop", at an angle of 45 degrees. - permission for careful movement. To distinguish semaphore signals in the night darkness, a gas lamp was used. Rotating, it shone in green or red.
An automatic system for switching traffic signals was invented and patented in Chicago in 1910. After a couple of years, the drivers got acquainted with the first electric traffic light having signal lights of the usual green and red colors. Oddly enough, this invention at that time was not patented.
What were the first traffic lights
Little by little the streets of the largest American cities (Cleveland, New York, Detroit) began to acquire traffic lights. Most of them had two signals - red and green, triggered by specially assigned policemen, sitting at intersections in glass booths.
Then, in 1920, the yellow signal began to be used in their designs. In Europe, the first traffic lights were installed in Paris, Hamburg and the cities of England. Designs with a countdown arose only in 1998, it happened in France.
In our country, the installation of the first traffic lights occurred in the early thirties of the last century. The very first was installed in Leningrad at the intersection of streets, now known as Nevsky and Liteiny Prospects. It happened at the beginning of 1930. About a year later, the first instance of a traffic light in Moscow, at the intersection of the Kuznetsk bridge and ul. Petrovka.
The role of traffic lights for modern vehicles
Nowadays, traffic on roads is inconceivable without such a powerful means of planning and organization as traffic lights. Their main tasks are to optimize the quality of traffic on the roads and achieve a high level of safety. Traffic light regulation is the most important tool of the general concept of traffic, consisting of measures to optimally organize the distribution of traffic flows, the safety of pedestrians and cyclists and the use of specific routes by vehicles.
For safety reasons, they are installed in places where there is a high probability of an accident, which can only be reduced by a constant regulation device. And also in cases where other measures (installation of prohibiting and restricting signs of the speed of movement, the device of unregulated crossings for pedestrians) are not effective enough.
Traffic lights must be installed in places where the priority rule is often not observed when crossing intersections. And also where traffic is characterized by high speed or intensity, with limited visibility and difficulties in determining the rules of priority of travel, with a small traffic capacity of the road section.
Their other role
Traffic lights, in addition, perform certain environmental tasks. For example, the so-called green wave aims to maintain a uniform flow rate and reduce the number of stops.
At the same time, less fuel is consumed, the amount of exhaust emissions and noise from moving vehicles are reduced. This factor is important in large cities on the streets with heavy traffic. Traffic lights also play an important role in ensuring the safety of cyclists and pedestrians.
What are they
By type and purpose, there are a huge number of models of traffic lights. There are modifications with arrows and without, two or three light signals, installed on level crossings or bicycle paths. All these are traffic lights. A pedestrian traffic light is arranged exclusively for the safe movement of people on the carriageway.
The most common, widespread types of them are road street ones. A pedestrian crossing with a traffic light can be found on the road of any country.
How is the traffic light
As you know, in designs for cars usually use all three traditional colors - green, yellow and red. When the traffic light is vertical, red is always above, green is from below. With a horizontal arrangement, it is red to the left of everything, green to the right. Part of the automobile is equipped with an additional section.
What is the purpose of the yellow signal? For traffic lights, this means the following: passage for the stop line is allowed, but the speed of travel to the area regulated by the traffic light must be necessarily reduced. That is, the driver must be prepared to switch the traffic light to red. This signal in a number of designs can be orange.
Types of regulation
Traffic control with traffic lights can also be different. With constant regulation, its mode is not subject to change and does not depend on the time of day or day of the week. Another view is adaptive. It to a certain extent depends on the size of the traffic flow. In this case, either the sequence, or the number, or the duration of the signal switching phases can change.
In other forms of adaptive regulation, all three indicators can change. The regime called the green wave is possible only with constant regulation or adaptive with a changing duration of light phases.
What about people?
Consider now non-transport - pedestrian traffic light. They are installed at officially registered pedestrian crossings. As a rule, they are equipped with only two signals - enable and disable. In appearance, designs for people may vary slightly among themselves. The most famous pedestrian traffic light - in the form of human silhouettes - green (walking) and red (standing).
Other countries may have other designations. For example, in the United States, a raised palm is a red signal. Sometimes instead of the palm or the little men you can see the inscriptions "stand" and "go." On the streets of Oslo, the prohibition signal of a pedestrian traffic light looks like a pair of human figures standing nearby in red.
All these difficulties imply convenience for people with visual impairments or color blindness, that is, poorly distinguishable colors. For the same purpose, in most countries, usually pedestrian traffic light signals are duplicated by sound.
Let's talk about its design
What is the design of a pedestrian traffic light? There are several options. One of them is based on incandescent or halogen lamps. The pedestrian traffic light in this case consists of the actual lamp with a reflector, a light filter, a Fresnel lens and a protective visor.
Other widespread traffic lights are based on LEDs. They have certain advantages, namely: a brighter color, a reduced likelihood of spurious illumination. In addition, they are less prone to destruction - in case of failure of a separate LED, the rest of the design remains operational.
In addition, the design of such a traffic light is simpler and consists of an LED matrix, anti-vandal glass and a visor.
Pedestrian traffic lights T 7
According to statistics, a quarter of all pedestrian rides occur at crossings for them that do not have traffic lights. At dusk and at night, it is sometimes difficult for drivers to notice a pedestrian crossing on time. What can be done to improve the security of unregulated crossings?
The best solution at the moment is to equip such crossings with T7 type traffic lights. These are yellow LED designs. They are capable of being seen by a driver from afar. And by means of a pulsed LED display, such a traffic light at dusk or in the dark will accurately warn the driver about the approach of a pedestrian crossing and the need to reduce speed. As a result, at the signal of such a pedestrian traffic light, crossing the road is much safer.
Such a traffic light is powered by the mains, the costs of its installation are mainly due to the cable laying procedure and the cost of the latter.
Solar Traffic Light
An even more effective solution would be a solar-powered LED traffic light. The cost of installing it is half that for laying a cable and fits in the amount of 40-50 thousand rubles. In addition, there is a significant cost savings on electricity.
The pedestrian traffic light on solar panels today is the achievement of the most advanced technologies. The installation of such a design does not imply digging a trench, connecting a cable to the mains and protecting it, and paying for electricity.
What are the benefits?
A set of LED traffic lights and solar-type mini-power plants are unmatched. Such a traffic light at a pedestrian crossing can be placed on the road sign itself and will begin to work immediately after installation. Its battery life is at least 8 years without any maintenance.
Due to the low energy consumption, such traffic lights are durable, its rechargeable battery can work without recharging in sunlight for three days.
In daylight, the battery is charged by a powerful solar battery. The charging process takes place even in winter or in cloudy weather. Thanks to the integrated controller, a full battery discharge never occurs.
Finally, it is worth mentioning that in Russia there is even a special monument to traffic lights! The sculpture was installed in 2006 on the street of Novosibirsk.