2 minutes to understand the reason why street lights are yellow instead of white

Introduction:
When driving at night, you may ask: Why are the street lights yellow instead of white or other colors? In fact, we tend to think of white light as more pronounced and yellow as darker. But the street lights are yellow; is it to bring you a little warmth when you come back at night? What is the difference between yellow street lights and white street lights? The following will introduce you in detail.

Why are street lights usually yellow or orange?
Why are street lights yellow and not white? First of all, we have to figure out why street lights emit yellow light. It depends on the bulb used. Most street lights are made with sodium vapor, which is mainly divided into high-pressure sodium (HPS) and low-pressure sodium (LPS). High-pressure sodium lamps are used more because of their high luminous efficiency, low power consumption and long life. Moreover, its fog permeability is also very good, making night travel safer and reducing the probability of traffic accidents.

However, high-pressure sodium lamps also have the disadvantage of poor color rendering. It was white when it was first opened, but it turned yellow after a while. No matter what the object is, it is yellow. After reading this, you may ask, why not use a clearer incandescent lamp? That’s because, for road lighting, color rendering is not that important. When driving at night, you only need to look at the size and shape of the oncoming car, not the color of the car.

Why is sodium used in street lighting?
Simply put, a street light is yellow or orange because it uses high pressure sodium; why is sodium used in street lighting?
First, let’s look at a table with the average rated life and lumens per watt of different types of bulbs.

bulb type
Average rated life
lumens per watt

incandescent lamp
750-2,000 hours
12-18

HPS
20,000-24,000 hours
80-140

led
40,000-50,000 hours
30-90

halogen
2,000-4,000 hours
10-20

We can clearly see that high pressure sodium lamps have about seven times more lumens per watt than incandescent bulbs and can last up to about 24,000 hours. Therefore, the sodium lamp is bright enough and has a long service life.
Another big reason is that it consumes less power. Because it only produces light visible to the human eye. Incandescent bulbs emit light in all frequency ranges from infrared to ultraviolet and are very power hungry.
Therefore, sodium lamps have obvious cost and efficiency advantages over other bulbs, so why not use sodium lamps? Since the 1980s, high-pressure sodium lamps have been widely used in street lamps, and people have gradually become accustomed to yellow street lamps.
Why not use LED street lights?
Street lights do not use incandescent bulbs for efficiency reasons, but why not LED street lights? After all, when we look at the table above, LEDs are highly efficient and have a longer average rated life. Two main reasons are described below.

1. Appearance time
In fact, it wasn’t until 1962 that Nick Holonyak invented the first visible LED light. This is much later than other types of lights. At this time, many street lights are already in place. The widespread application of new technologies requires practice, which cannot be accomplished in a short period of time.
2. Cost
LED lights are also expensive. An LED bulb cost about $200, which was a lot of money at the time. Street lighting requires not only light bulbs, but also poles and other materials. Installation is also labor intensive.

But over the years, the price of LEDs has been falling, and some street lights have begun to use LED lights. There is no doubt that as the technology advances, we will see LED technology used in more areas. But we need to know that LED lamps will not replace sodium lamps when sodium lamps have no obvious disadvantages.
Best LED Street Light Manufacturer
If you want to buy high-quality LED street lights, you must choose a reliable LED street light manufacturer, and then your buying journey is half done.
BBIER is one of the best LED street light manufacturers in China. It is even well-known in China for its decades of experience in manufacturing and exporting street lights. BBIER street light manufacturers can provide you with a variety of high-quality LED street lights and high-quality services!
Here are some popular LED street lights for your reference.

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