LED Lights Knowledge & Tips

Why is it BETTER to Use Warm or Yellow Color for Street Lights?

why street lights are yellow

Nowadays, LED street light is gradually replacing sodium vapor, halogen, HPS or fluorescent, and becoming the most popular option for outdoor roadway lighting because of its higher energy efficiency yet lower greenhouse gas emission. But have you noticed that most street lights you see, no matter on highway, pavement or alley, are not purely white; instead, many street lamps have yellow orange color. Why?

To know the rationale behind, we’ll need to know what the “color” stands for. 

Color temperature (CCT) determines the street light colors

kelvin-scale-for-street-lights

Color temperature is a way to indicate whether the color is cool or warm. As you can see, the lower the CCT is, the yellower the color looks. For instance, the 2000 to 3000K on the scale have an amber or orange tone. But as the CCT increases, the color starts to switch from yellow to white, and eventually becomes bluish white, or the cool color.

Why street lights are usually yellow or orange in color?

Better transmission and penetration through fog

This is a vital factor that needs to be considered when you are looking for a suitable LED street light for your project because it is closely related to the safety of drivers and passengers. Yellow light is proved to have better transmission than white or cool street light. Apart from that, the problem of urban sky glow (lighting pollution) is attributed to street light that has low penetration ability. The lighting pollution on sky influences the astronomical researches because observers cannot have a clear view of the star movements when the sky is too bright.

yellow-street-lamps-is-very-common

Less physical impact on people

According to recent researches, the blue light will suppress the secretion of melatonin which is a hormone that helps maintain our internal clock and affects our emotion & reproduction. It is also proved that the hormone has a great impact on our immune systems. And thus, many countries are prone to adopt yellow or amber street lamp that eliminate the blue color for the residential areas.

Less impact on Eco-system

Introducing street light producing lights similar to daylight in rural areas will mess up the metabolism cycle of plants and animals, especially for nocturnal animals. The bright white light interferes their perception of day and night, and thus affects their hunting, migrating in their lives. For example, the turtles are attracted by white light, and they are crashed by cars when they reach the road. Since the sea turtles are more sensitive to white than yellow lights, turtle friendly yellow street light is compulsory in some countries such as US.

yellow-led-street-light-products

Type of bulbs used

When LED was not so common, sodium vapor was the mainstream technology for street light. Due to its characteristic working principle (such as electron excitation and gas discharge), yellowish orange light is emitted. However, the service life of the traditional gas discharge lighting is not very satisfactory – frequent replacement is required. Nowadays LED street lamp works for at least 80000 hours without significant lumen depreciation.

From the above reasons, warm light is more common and better for street and public lighting.

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