Why Does Only One Headlight Work on Motorcycles?


You may have noticed a motorcycle approaching you on the road, and it only has one headlight. Many people assume that this is because the other headlight is not working for some reason. In actuality, there is a safety reason why many motorcycles only have one working headlight.

Only one headlight works on motorcycles because it is meant to indicate to oncoming traffic that it is not a car. In essence, motorcycles are signified by one working headlight, while other vehicles are signified by two. It also indicates that the motorcycle is likely quite close in terms of distance.

There is much more that goes into the decision to only have one working headlight on a motorcycle. If you are interested in the safety aspect of driving on open roads, the following guide will help determine how to avoid accidents now and in the future.

Why Do Bikes with Two Headlights Only Use One?

R6 Yamaha, parked with one light on

If you look at an older motorcycle, it is likely that it only has one headlight, to begin with. However, modern motorcycles do tend to be designed with two headlights. The question becomes why only one seems to work unless the driver specifically activates the second one.

A couple of the more commonly cited answers to this are:

  • Functionality – From a functional perspective, motorcycles only need one headlight with a dimmable feature to work correctly. Because the headlights on a bike are very close to one another to begin with, it is not really necessary to turn both of them on for any reason. 
  • Depth Perception – One of the critical functions of headlights is for other drivers to judge how far away another vehicle is at night. Since two headlights on a motorcycle are close together, approaching drivers cannot judge distance with any accuracy level unless only one is used. Two headlights are much more useful on cars and trucks. 

To provide even more clarity to this answer, we go back to the concept of triangulation. This is the process of measuring distance via angles. Our brain does this automatically when we look upon an object with our eyes. The closer we are to an item, our eyes will look at it more narrowly.

The farther away an object is, the more difficult it is for us to perceive distance. This is because the angle becomes smaller. With the headlights on a car, we see two lights from only one perspective. This is not possible with a motorcycle because the two lights would be too closely aligned together.

Why Are Bikes Now Built This Way?

Red Yamaha R6 with both lights on

Since it is not prudent to use two headlights on a motorcycle, the next question becomes why build them this way in the first place. The most logical answer is that it is done from a design perspective. People expect there to be two lights, even if they use only one of them. Many motorcycles today still only use a one headlight design. 

Some bike manufacturers have made use of the second headlight by turning it into a dimmable light instead of having two lights that dim. This ends up saving money as well. It also enhances safety and creates a more aesthetic look that many motorcycle enthusiasts have come to appreciate.

Are Passing Lights Useful?

For motorcycles that have two lights, many will incorporate passing lights into the design. This is a much safer way to drive the bike in low light conditions than using high beams on a continual basis. They will not give off as much light as a high beam would, but it does provide more illumination than one single headlight.

The idea is that drivers are safer when using passing lights because they will essentially use three lights instead of one. They have become so useful that many motorcyclists will pay to have them installed if their bike does not have that feature.

How To Increase Visibility When Riding a Motorcycle

It is always helpful for a motorcyclist to more clearly see the road ahead of them without impacting the visibility of oncoming traffic. That is where the debate over one versus two headlights comes from in the first place. Traditionally, one headlight on a bike is meant to be the low beam, while the other one acts as a high beam when necessary.

While this design is functional, it does lower visibility for the average motorcycle driver. The question, then, becomes how to increase the visibility without compromising safety. There are several ways to do this.

  • Change the type of light on your motorcycle – If you are using halogen lights (more on this in the next section), consider upgrading them. They are simply not that bright, making it more difficult for other drivers to see you. LED lights are considered to be much more suitable for this purpose.
  • Alter your clothing – If you want to make sure you are seen, particularly at night, you might want to look at what you wear. While motorcyclists tend to wear black, this is the worst color you can choose from a visibility standpoint. At the very least, you will want to invest in a brightly colored jacket and helmet to help you stand out from other objects on the road.
  • Put some color on your bike – You can also add some color to your bike. This does not mean you need to take it to the body shop to be painted. A couple of pieces of reflective tape and some color strips here, and there will do the trick just nicely. 

While having just one motorcycle light does not decrease your visibility, there are other factors that do. As a driver, you can do your part to complement the lights on your bike and ensure that you remain safer on the open road. 

3 Types of Motorcycle Lights Used Today

Suzuki with light on in the night

Since you only have one light to work with on a motorcycle, you want to make the best use of it that you can. Three different types of lights tend to be installed on motorcycles today. 

  • Halogen lights are the oldest types of lights that there are, so you will not typically see them on newer bikes. They are not bright in comparison to other lights, and they are not energy efficient. 
  • Xenon HID lights are actually the brightest of the three types of lights, but they are not very energy-efficient. They also tend to be quite fragile due to the high level of heat emission that they give off. 
  • LED lights – These have become the most common type of lights in use on motorcycles today. They are brighter than halogen lights, and they do not cost as much. They are durable and have a low heat emission. From just about every perspective, this is the one motorcycle light that drivers prefer today. 

If you have a halogen light on your motorcycle, you will want to consider changing it to an LED. These are much safer. You will be seen more clearly by oncoming traffic. LED lights also provide drivers with a clearer overall view at night, which is essential when driving in low light conditions. 


The next time you see a motorcycle approaching with only one headlight in use, you will know that it is not because one of the lights is burnt out. There is an actual reason why only one headlight tends to be used on a motorcycle, and it is one based on safety and the way humans judge distance and depth perception. 


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