It’s time to climb up here on this soap box and hold up a big red and white target. Time to dip my toes in the muddy water of LED lights. Just to clarify, this article is a matter of opinion, with some facts thrown in for good measure. Let’s get started.
Are LED lights legal? Yes, no, and sometimes both. Usually if there is some doubt, we can refer to federal and/or state laws for clarification. FMVSS (Federal Motor Vehicle Safety Standards) section 571 explains motor vehicle requirements and is currently about 1200 pages. SAE (Society of Automotive Engineers), NHTSA (National Highway Traffic Safety Administration), and DOT (Department of Transportation) all have some input and regulatory oversight to those standards. What’s clear is that any modification to a vehicle that changes the way it was released from the manufacturer would be considered a violation of federal law. Unless those modifications meet the safety standards of the FMVSS and have passed stringent safety testing. For example, if an aftermarket suspension company sells a lift kit for use on the highway it must pass the safety testing before it can be certified for on road use. This applies to all vehicles operated on US highways. That is why you will see the “For off-road use only” on a lot of aftermarket products. The only exception regarding lights, is fog lights. They do not fall under the FMVSS regulations and can be legally modified with LED lights. Individual states also have their own vehicle light laws. When it comes down to it, the state laws are the ones that are more likely to be regularly enforced. Here in Minnesota, they usually look for functioning lights. If a light is burned out or missing it will likely lead to a vehicle stop. When all your lights are working, whether LED or not, it lessens the chance you will be pulled over. There are divisions of the Minnesota State Patrol that specialize in enforcement of vehicle safety standards. If the modification violates state or federal law they can site you for the violation.
Generally, replacing your marker lights, turn signals, or brake lights with LED bulbs will not get you into any legal hot water. They illuminate like the more traditional incandescent bulbs and in most cases are covered by colored light lenses. Where LED bulbs may cause problems is with computer monitored systems. The integrated keyless entry and remote start systems are monitored by the BCM (Body Control Module) and the BCM controls the output of a lot of the lighting systems. The BCM is programmed to look for a specific current draw for each circuit. When the current draw changes the BCM lets the driver know there is a problem with that circuit. For example, the turn signal might flash fast on one side or you might see a notification on the dash. One of the key benefits of LED lights is the reduced current draw. So, when you replace a standard bulb with an LED bulb the BCM says “Oh no, there is a problem here” and notifies the driver. There are ways around this problem, but it is usually best to leave the proper light bulb in the monitored light circuits. Which is most of the vehicles sold within the last 10 years.
Headlights are the source of most of the LED light controversy. Let’s start with the law and expand from there. According to FMVSS, the only way a vehicle with LED headlights is legal is if it came from the manufacturer that way. There are regulations about the reach, aim, and width of the headlight patterns. All of which are very hard to measure in the real world. Minnesota law also has some headlight reach regulations. You are also limited to four, forward facing headlights. What is most likely to be enforced is the number of working headlights. This means that all LED light bars are not legal to use on the road.
What are the advantages and disadvantages of using LED headlights? The main advantage is the driver can see better at night in most driving conditions. A lot of this is due to the color temperature of the LED lights. Which is measured in Kelvin. Most LED headlights are in the 5500-6500 Kelvin range as opposed to tradition halogen lights which are around 3000 K. This is part of the reason LED lights are so blinding to other drivers. Imagine you walk outside on a bright sunny day. Even though you are not looking directly into the sun, it still seems bright on your eyes. This is because the light from a sunny day is around 5000-6500K. Now think about driving around at night and looking into a bright sunny day. I can see you squinting now. The other factor is light disbursement. Composite headlight assemblies are designed around a particular bulb with a very specific light location within the assembly. The reflector and lenses are developed to cast the light from that bulb a specified distance and pattern. As dictated by FMVSS. When an LED bulb is installed into a halogen light housing, it can cast the light differently. Because the light point and shape of the LED differs from the original Halogen bulb. LED lights typically disperse light near and wide as compared to a standard halogen bulb. That is part of the reason that most LED bulbs are rated with a higher lumen value than a standard halogen bulb. Think of lumens as the raw power output of a given light source. Since the LED bulbs emit the light in near and wide pattern, they need more lumens to reach out to a similar distance of the halogen bulbs. A more accurate way to measure the light output from a vehicle would be to use Lux or Candela. Lux is a measurement of the amount of light within a 1 meter square on the wall, measured 10 meters from the light source. Candela (aka Candle Power) is the intensity of light produced in a certain angle and direction. This is more of a real world measurement of how much useable light is cast downrange from the light source. If you were to measure the Candela of a halogen headlight and compare it to the same vehicle with LED headlights, you would find that they are very similar.
LED advantages
Driver can see better at night in most conditions due to LED color temperature.
Wider light disbursement can help illuminate side hazards.
LED lights last longer than halogen bulbs.
Lower power draw.
Many options available for replacement bulbs.
LED disadvantages
Not legal in most situations.
Can cause BCM monitored circuits to freak out.
Can cause light glare to vehicle driver during snow, rain, and fog.
Light glare is harsh to the drivers of oncoming vehicles.
Cost more than traditional bulbs.
Market is flooded with low quality bulbs and light assemblies.
There can be fitment issues.
LED lights run cooler and can be subject to ice buildup in the winter.
Final thoughts. Generally, aftermarket LED headlights are illegal for use on the road in the US. If you choose to install them anyways, they can provide a benefit to the driver of the vehicle in most operating conditions. Due to the design and poor function of the factory headlights on my daily driver. I chose to upgrade to LED headlight assemblies, and I now enjoy driving the vehicle more at night. When I drove other vehicles with halogen lights, I found myself missing the whiter light of the LEDs. If you decide to install LED headlights, I recommend replacing them as a complete light assembly designed around the LED light source. This provides a more controlled, useable light pattern down the road. Manufacturers of high-quality light assemblies are more likely to better adhere to the FMVSS and may offer them with a legitimate DOT test rating. They are more expensive, but worth it for the quality of the light output and longevity of the bulb. If you choose to install LED bulbs in your factory halogen headlight assemblies, I recommend getting them aimed. It can help to reduce the number of times you get flashed from people thinking you have your high beams on. Are the advantages of the LED lights worth dealing with the disadvantages? It all comes down to driver preference.