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Why Do LED Street Lights Use Warm Light

Jun 12, 2019

Why Do LED Street Lights Use Warm Light


Today, LED street lights are gradually replacing sodium vapor, halogen, HPS or fluorescent lamps and are becoming the most popular choice for outdoor road lighting because of its higher energy efficiency and reduced greenhouse gas emissions. You may notice that most of the street lights you see, whether on highways, sidewalks or alleys, are not pure white, but yellow-orange. But do you know why different applications use different color temperature?

Color temperature (CCT) is a way to indicate whether the color is cool or warm. As you can see, the lower the CCT is, the more yellow the color looks. For example, 2700 to 3000K on the scale above has an amber or orange tone. But as CCT increases, the color begins to change from yellow to white, eventually becoming blue-white or cool white.

After knowing the meaning of the color temperature and the comparison of different color temperature. Let’s explore the main reasons for the question above.

1. Better transmission and penetration through fog

This is an important factor to consider when looking for the right LED street light for your project, as it is closely related to the safety of the driver and passengers. It turns out that yellow light has better light transmission than white or cold light. In addition to this, the problem of urban sky lighting (lighting pollution) is attributed to street lamps with low penetration. Illumination pollution on the sky affects astronomical research, because when the sky is too bright, the observer cannot clearly see the movement of the star.

2. Reducing the physical impact on people

According to recent research, blue light inhibits the secretion of melatonin, a hormone that helps maintain the internal clock and affects our mood and reproduction. It turns out that this hormone has a big impact on our immune system. Therefore, many countries tend to use yellow or orange street lights to eliminate blue in residential areas.

3. Less impact on ecosystems

The introduction of daylight-like streetlights in rural areas can disrupt the metabolic cycles of plants and animals, especially at night. Bright white light interferes with their day and night perceptions, affecting their hunting and migrating in their lives. For example, turtles are attracted by white light and they are hit by cars when they reach the road. Because turtles are more sensitive to white than yellow lights, turtle-friendly yellow street lights are mandatory in some countries, such as the United States.

4. Type of bulb used

When LEDs are not common, sodium vapor is the mainstream technology for street lamps. Due to its unique working principle (such as electronic excitation and gas discharge), it emits yellow-orange light. However, the life of conventional gas discharge lighting is not ideal - it needs to be replaced frequently. Today, LED street lights work for at least 80,000 hours without significant lumen depreciation.

In summary, warm light is more common and is more suitable for street and public lighting.