Why are There Three Different Lights in Traffic Signals?

There are many concept designs for traffic lights on the internet. Among these concepts, you can find very interesting traffic light designs. Different colors can be contained in a single module or by showing some animations, it promises to make traffic a little more fun. Today, it is technically possible for all colors to be placed in a traffic light and it also benefits in terms of cost. So why are three separate lamp bodies still used for three different colors?

Because the location of the light is as important as the color of the light for drivers. The colorblind drivers and the pedestrians can understand which color is light up by the position of the light. On vertical traffic signal heads; the red light is placed at the top, on horizontal traffic signal heads; the red light is placed at the left. Those positions mean stop for colorblind people.

On the other hand, we are all experiencing color blindness under certain circumstances. It is known that the vision of the human eye is approximately 180 degrees. However, only 90 degrees of color vision conditions are formed in this part. After 30 degrees from the fixation point of the eye, the ability to see color starts to disappear. After this point, people start to lose their ability to distinguish colors. It starts to act like a real colorblind at 50 degrees and above.

A qualitative representation of visual detail in a single glance of the eyes.

The above image shows how colorful and sharp we see in the middle of the field of view, in peripheral areas, how color vision decreases has been shown. This represents a real vision from the human eye.

The ability of human eye to perceive color, shape and text.

The other area where the human eye is more successful than the color detection is the ability to detect movements at extreme points. The movement of objects within the visual field is easier and more detailed. Instead of looking at the traffic light directly while traveling or waiting at traffic lights, it keeps this light within our range of vision, we watch the road and the other vehicles. For this reason, we notice that position of the light changes before the color of light in traffic lamps.

If all the colors in a traffic light were contained in a single body and the light color of this body changed according to the signalization status, it could not be seen that the light turned from green to red. For this reason, the important thing in traffic lamps is not only the color of light but also the position of the light. This makes traffic lights more noticeable, a safer environment can be created for drivers and pedestrians.

EN 12368, EN 50556 international standards clearly define the requirements for traffic signal lights and road traffic signaling systems. Traffic lights and signaling applications to be used on all roads in the city and intercity should also comply with these standards. Apart from this, world-wide practices should be taken as examples and local differences should be avoided.

Written by Emre Yılmaz – Aydınlatma Portalı, Asya Traffic Inc.