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IN 1940, the Society of Automotive Engineers said, “Let there be standardized automotive lighting.” And the lighting was good. But not as good as Europe’s. Things evolved over the years. U.S. headlights got better, but so did Europe’s. Today, they’re different, and it’s not so clear whose headlights are better.

Here’s a glossary of automotive headlighting. It’s in chronological order, not alphabetical, with some personal opinions tossed in for good illumination. Today’s topic is hardware; a following one will be on measurement units and regulations.

BSB. The earliest cars were Before Sealed Beams and had a variety of forward illumination left over from the carriage era.


Carbide lamp, c. 1905. Image from

Around the turn of the century, carbide lamps dripped water onto calcium carbide, thus producing acetylene, illumination and the occasional explosion. In 1912, Cadillac’s lighting by electricity was a decidedly better idea.

Sealed beams. In 1940, the 7.0-in. round sealed beam was given SAE blessing and the government’s. It was the only headlight design allowed in the U.S. for 17 years.


Sealed beam lamp, the default North American illumination from 1940 until the 1980s. Image from vampshow.

In 1957, sealed beams continued with permitted quad systems downsizing the circular diameter to 5 1/4 in. In 1975, rectangular sealed beams of commensurate size became legal.

The tungsten filaments of these sealed beams produced a soft blob of orangish light. Sealed beams of these standard sizes were available in just about any drugstore for a dollar or two.

Halogens. By contrast, Europeans have regulated their headlights by performance, not size or electrical innards. During the 1960s, they (and the rest of the world) adopted lighting with separate bulbs of tungsten filament glowing in a halogen atmosphere. The halogen family of elements includes astatine, bromine, chlorine, fluorine and iodine, this last one common in halogen bulbs.


Today’s standard automotive lighting. Image from CoolKoon.

Halogens (aka quartz halogens) are more efficient and last longer than traditional sealed beams. Compared with the warmth of traditional tungsten incandescence (and campfires), halogens provide a bluish illumination.

Being non-standardized, their lens housings give stylists unprecedented freedom and their automotive designs fresh faces. And, as a tradeoff of non-standardization, halogen headlights are a lot more expensive to repair or replace than sealed beams. U.S. halogen bulbs came in 1983 and continue to be the default headlights on many new cars.

Xenon HIDs. First in Europe and by 1996 in North America, xenon headlights swapped glowing incandescence for an electric arc, a high intensity discharge in an atmosphere of a rare gas, xenon.


HID lamp illuminates by electric arc, not incandescence. Image from

Compared with halogens, these bulbs are doubly efficient, last more than twice as long and are more than three times the cost. They’ve been fitted to premium cars for a while now, with growing availability on more mundane machines.

There remains a controversy that old people are driven crazy by the enhanced bluish cast of xenon headlights. Do you suppose this is related to chem trails?

LEDs. Light Emitting Diodes produce illumination through electroluminescence of solid-state electronics. Initially available only in red, white-illumination LEDs are now common, making them feasible for automotive headlights. These are typically fitted in arrays of directed pencil beams.


LED array, Audi A8.

LEDs are durable, compact and energy-efficient—and still pricey. Data from 2013 suggested a standard halogen headlight might cost an automaker $20; a xenon counterpart, perhaps $60 to $80; and an LED-array equivalent roughly twice the price of a xenon.

Specialists predict that by 2020, LEDs will account for 20 percent of automotive headlighting worldwide. These LED arrays give stylists even more artistic freedom, if you happen to like that sort of snarky automotive face. (And, no, I am not wedded to sealed beams.)

Lasers. The most recent automotive headlighting uses laser technology. Its bulb has mirrors to direct a laser onto a surface that emits light. Such a luminescent surface is called a phosphor, not to be confused with the element phosphorus. This element’s light-emitting behavior is chemiluminescence, not phosphorescence. A phosphor’s light emission is a combination of phosphorescence and fluorescence (this last, as in fluorescent lighting).


Laser technology generates illumination through luminescent surface.

The principal advantage of laser lighting is its efficiency, twice as good as LEDs. At this point, it’s premium automotive lighting, used on the BMW i8 for its high-beam function.

Dynamic beam control. The 1948 Tucker has a Cyclopsian central headlight that illuminated a path dictated by its driver’s steering. Today about 34 percent of all 2015 model cars have dynamic beam control of one sort or another. And, given the influence of the Insurance Institute for Highway Safety, more are likely to do so before long. IIHS plans to include headlight ratings in its assessment of cars as early as 2017.


The 1948 Tucker’s central headlight rotated with steering angle. Image by Thomas.

Cornering lights actuated by directional signals are the most common dynamic beam control today, some simply using the front parking light on that side to enhance illumination. Systems that sense on-coming traffic and cut high beams have been around for years as well. Europe has required lens washers and automatic self-leveling of xenon systems; the U.S. and Canada permit the technology.

The multiplicity of lights in LED arrays encourages directional intensity variation. This can be keyed to sensors identifying on-coming traffic or surroundings, and also to steering input and speed of the car carrying the smart illumination.

I appreciate corner illumination that’s invoked by a car’s directionals. I’ve not tried more advanced systems. However, I suspect I might find their independent control a bit disconcerting, the visual analog of commercial messages on TV or radio that are jarringly boosted. What do you think?

This glossary continues next time with some lighting measurement units and aspects of regulations. ds

© Dennis Simanaitis,, 2015


  1. Bill Urban
    December 29, 2015

    BMW’s adaptive xenon lighting smoothly pivots up to 15 deg. with the steering, and, auto-levels. That, and the near side fog light illuminating at low speed with turn signal and/or steering angle are serious advantages for older eyes . . .
    Agreed, “snarky” is the word for most of the LED arrays, but not, in my estimation, for the corona rings, suitably understated.
    Next up, roof mounted laterally aimed lights (for drifting:-)

  2. Mike B
    December 29, 2015

    The “old people” problem with xenon-arc & even some LED lamps isn’t chemtrails. It’s cataracts and other forms of visual disturbance, or even less-than-perfect-condition glasses, that enhance the glare of the extremely bright, point-source light. The color is an issue, too, with blue tending to scatter more than red. Yes, it *is* a problem and I’ve been bothered by it; some lights are literally painful. Halogens are much less easier on the eyes, and easier to see by. OTOH, red dash illumination, especially if its brightness is limited (looking at you, Mazda), can be a problem with older eyes too. Balancing act, as usual. And yes, I agree that too many LED arrays are “snarky” looking.

  3. Skip Cusack
    February 9, 2016

    While I agree that modern lighting technology is a boon for designers, there were some lovely old tech lights back in the day such as the Lucas PL700 tripods and the icon Flamethrowers. Marchal also made some lovely products. My old British MG sports Lucas (of course) and there are semi-modern bulbs available for them now, for the best of both worlds. Well, …almost.

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