Why do Some Cars Have Blue Headlights?
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.
Written By: Chad Upton
Photo: MSVG (creative commons)