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Traffic light

Did you know the first traffic light actually exploded injuring its operator?

The first traffic light ever was installed on December 9, 1968 in London outside the House of Parliament to control the traffic in the nearby three streets.

Based on all the future developments, traffic lights can be classified in various ways.

Traffic light
Traffic light

Classification on the basis of the automation of traffic lights:

There are two categories of traffic control system: A fixed system and a dynamic one. The dynamic traffic control systems can be further classified based on the types of detectors used in them.

The fixed traffic light control system is configured to switch lights after a certain period of time. The time interval depends on the region and traffic values. It has a controller that moves with dial timers to be able to display a certain color for a small interval of time.

Dynamic traffic control systems, on the other hand, are more appropriate as they are able to adapt their settings according to the crowd present at different times of day.

When a car passes over the Embedded Detector, it simply sends the information to the traffic light. In this way, the traffic system which can already control the timing by itself, knows for sure that there’s a line of cars waiting for the signal to go green. This kind of detector is generally expensive due to its cost installation and maintenance.

Mounted Detectors are quite affordable and its installation is not affected by any other systems located in its proximity. Not only these are inexpensive, but they also send over more information to the traffic lights which include real-time photos.

Classification on the basis of the use of a traffic signal

Let’s look at the following categories:

Junction Signal:

This signal control vehicles coming towards a certain junction in a contradictory manner. With the help of a camera mounted on it, it monitors and responds to the flow of traffic, whether heavy or light.


It facilitates the street crossing for people. This signal displays a digital dotted green-man signal or a red-man signal crossing for a fixed interval of time. Hence, it indicates for common people, according to its color, when it is safe to cross the street and when not.


This signal controls a shared crossing for common people and cyclists. It is usually wider than the Pelican Crossing mentioned above. It has standard red/green/yellow signals with a green digital cycle next to the man hence controlling the traffic of both of them (Cyclists and Pedestrians) at the same time. When the Toucan is busy, detectors help it by increasing the crossing time.

Equestrian Crossing:

This is mainly used by horse riders and more than often referred to as Pegasus crossing. Red and green horse signal display helps the riders to know when you can cross the street and when not.


Last, but not least, this is the one we all are very familiar with. It is again a pedestrian crossing facility. This mostly works in combination to the traffic light. When a pedestrian steps on to this area, a motorist has to give way. This crossing also has orange flashing light at both its end to indicate the presence of the crossing.

Zebra crossing
Zebra crossing

Traffic Signal Color Coding:

Red was the color that denoted blood and thus it was selected to stop the vehicles. It became the symbol of danger. Also, even in misty environment, red color could be seen from far distance and hence avoided fatal collisions.

Green symbolizing nature was chosen as signal for relaxing as observed by human emotions. And it was clearly visible at the night time and since it is quite a contrast in comparison to red and yellow, it would never create confusion for the drivers.

As for Yellow, most people believe that it symbolizes sun and is taken as a sign of caution.

Over the years, traffic lights have evolved although maintaining the basic colors to accommodate people suffering from color blindness. Red-green color blindness, these days, is the most common form of visual impairment. Hence the red light comes with a little orange and green comes with a little blue to address this socio-medical issue.

We can conclude that traffic lights were a great invention for all of us. But what if I tell you can build one too? That way you could teach him about this simple invention that we use in our day to day lives. Don’t worry; you can get the raw materials from Projects For School-Traffic light DIY Kit. If you are a parent who believes in “Practical is always better than just theory “then this is the ‘go to’ place for you.  Explore it. You just might find a great science project for your kids this semester!




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