Why do Some Cars Have Blue Headlights?

April 2, 2010 at 12:46 am 17 comments

Traditionally, cars have had yellowish headlights. Now, many cars have light blue colored headlights. Some cars come with those headlights from the factory and other times, owners will install similar systems or similar looking systems.

The factory blue headlights are known as HID (high intensity discharge) headlights. Just like the name describes, they’re brighter than normal halogen headlights.

Traditional lights heat a small metal filament to produce light while HID lights create a plasma discharge arc between two tungsten electrodes. It is this plasma discharge that creates the blue color. But, this technology is not new, it’s very similar to the bright lights that illuminate stadiums and roadways.

The brightness is the main advantage of these lights. Like rear fog lights, these headlights were popularized in Europe where fog, rain and curvy roads create demanding driving conditions. Because HID lights are brighter, they penetrate fog, rain and snow better than halogen lights — an advantage when the conditions are not ideal.

HID headlights are also more energy efficient than halogens, which isn’t a major concern in vehicles right now, but as we move to battery powered cars that will become very important — the less power accessories consume, the further the vehicle can drive on a single charge.

If they’re better, why don’t all cars have them?

They’re not better in every way, they do cost more. I mentioned that they are similar to stadium lights, except stadium lights require a lot of warm up time before they are really bright. HID lights often reach 75% brightness within a few seconds and achieve 100% brightness after a couple minutes. This quick start-up is made possible by a ballast and ignition control module in the vehicle that provides a 20,000 volt pulse to initiate the arc.  These components along with the bulbs themselves increase the cost for manufacturers to install these types of lights.

Vehicle conversion kits are available for many vehicles and they usually begin around $300. But, you can’t put these bulbs in any headlight socket. In the US, it is illegal to change the type of bulb that your headlights were originally approved for by the Department of Transportation (DOT) and similar laws exist in most other countries.

Because HID lights are brighter, the DOT pays very close attention to the aiming of these lights. If you see HID lights that are “blinding”, it’s generally because somebody has installed the bulbs in an unapproved headlight fixture that is not designed to focus the light down and away from your eyes. Approved headlight fixtures have a very sharp projection pattern that keeps the light out of oncoming eyes. In some European countries, HID system are required to be auto-leveling so that heavy loads in the rear of the vehicle do not pitch the light up into oncoming traffic.

For left hand drive vehicles, the right headlight is actually aimed slightly higher than the left to improve visibility on the right side of the road (street signs, peripheral dangers…etc) while the left side is aimed lower to keep it out of oncoming eyes. If you’re driving in front of a car with HID lights, it may appear that their right headlight is improperly aimed, but it is likely that it is intended and should still be a reasonable brightness. Many systems calibrate every time the vehicle is started to ensure they are properly aimed and do not “blind” any other motorists.

There are also tinted bulbs available that look similar to HID systems. They are not as bright as HID headlights, but they can often be installed legally. Many bulb manufacturers have introduced brighter and whiter halogen bulbs to give buyers a reasonably priced alternative to traditional bulbs.

Broken Secrets

Written By: Chad Upton

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Sources: MVLC, Smart Motorist

Photo: MSVG (creative commons)

Entry filed under: Automotive, Be Efficient, Demystified. Tags: , , , , , , , , , , , , , , .

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17 Comments Add your own

  • 1. pramunindyo  |  April 23, 2010 at 9:15 pm

    it;s maybe had something to do with the color wavelength too as the shortest color wave is blue and the longest is red, and it cause our eyes to see a blue emitting light is faster than any color. but that is only maybe

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  • 3. Addierun  |  March 15, 2012 at 4:05 pm

    I find the blue lights hurt my eyes, even if I keep my eyes along the side of the road. I do not like.

    • 4. Paul  |  March 17, 2012 at 10:43 am

      If they’re factory installed they have automatic leveling systems, so they are always aimed below your eyes and they are actually less offensive than traditional headlights. HIDs get a bad name when people install them in cars and motorcyles that are not designed for them and then they hit your eyes.

      • 5. kbd jhg  |  April 12, 2013 at 8:05 am

        No. Leveling or not – just an excuse – these bulbs are hated because they emit a blue light like a blow torch and they hurt your eyes. We hope some day the DOT will ban them.

  • 6. ProModder  |  November 28, 2012 at 10:52 pm

    HIDs that come from the factory are not blue. The reflector bowl in the projector refracts the light at the cutoff, making them appear blue, because they are aimed just below eye level so they dont blind you. The light coming out is actually white. The more you know!

    The problem is the aftermarket HIDs that kids put in do not know this, resulting in them buying actual blue HIDs that are going to blind you and hurt your eyes, mostly because they are not put into projectors like they are supposed to be

  • 7. Terry  |  February 21, 2013 at 10:10 pm

    Who authorized the use of these lights? Was there any data to show how they affect different ages of people? These lights are very blinding even when trying to look to the side away from them. There was no need for these bright lights. When you go around a corner or over a hill and they are suddenly there you are blinded. When people pull up from behind you get blinded by the inside mirror and also the side mirrors. These are not helping they are hurting more drivers and hopefully others will speak up.

    • 8. ddd  |  July 23, 2020 at 1:49 am

      I just adjust my mirrors so it puts light right back into their face and they back off

  • 9. TopGearUK  |  April 13, 2013 at 10:03 pm

    They have them all over Europe and I am guessing most of the comments here are not form europe but the usa because in Europe everyone has them they come with the car. Plus not many people complain about them here, they actually help. When weather get bad they help to drive through snow and fog.

  • 10. Fixit Man  |  August 31, 2015 at 6:24 pm

    I’ve been in vehicles with these, installed at the factory, and you can’t see ANYthing with them. They appear about as bright as moonlight, and you can’t distinguish even a curb from the road. Maybe it’s my partial colorblindness, but I prefer the yellowish lights any day, I can actually see by them. In snow, these things didn’t light up anything at all. I think one reason fog lights are even more yellow than regular headlights is that the yellow shows up much better through the fog or snow. These, I could see absolutely nothing other than some sort of indistinct glare outside the car.

  • 11. dawn  |  January 27, 2016 at 3:57 pm

    Is there any legal action groups working on illegalizing them?? I have heard so many complaints everywhere. They make night driving very difficult because my eyes have to re-focus… They outlawed tinted windows These should also be.

  • 12. Ken Crompton  |  January 28, 2016 at 8:28 am

    I object to these lights also, even a slight frosting from road grit on the windshield defuses the light to make it very difficult to see. These lights are just as dangerous in daylight also, you can pick them out from regular lights from half a mile away. The color also interfers with some traffic signals making them seem like the bulb is out. The DOT fell down on the job by not banning them earlier.

    • 13. Ag  |  January 15, 2021 at 5:48 pm


  • 14. Wayne  |  May 31, 2017 at 9:58 am

    I agree with the criticism….these blue lights physically hurt my eyes

  • 15. alex nicolas  |  March 14, 2020 at 4:12 am

    i completely agree with your points .specially i fell very disgusting when the opposite driver never fell to reduce the veem of there car and truck specially on hazy and foggy weather .i understand the concern about eyes problem , but it should be checked out

  • 16. Derrek Q. Davis  |  April 16, 2020 at 9:00 pm

    Are blue headlight lrgal in all 50 states of the country ?

  • 17. Ag  |  January 15, 2021 at 5:46 pm

    Blue lights and LED lights impair my vision while driving even when behind me. They should be illegal.


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