The first headlights to adorn automobiles weren’t all that much better than squinting real hard and hoping any cows in the road had the good sense to move out of your way. The dim light cast by early kerosene oil and acetylene gas lamps made most travel after dark a fool’s errand.
Today, of course, the latest generation of headlights work much like modern televisions with tightly packed arrays of pixelated lights blinking at up to 5,000 times a second, allowing drivers to essentially use high and low beams at the same time. Until very recently, however, cutting-edge features like that weren’t allowed on vehicles sold in the US due to an NHTSA regulation set in the 1960s. But thanks to a multi-year lobbying effort on the part of Toyota, those regulations changed this last February — now America’s roadways are about to become a bit brighter and a whole lot safer.
How headlights evolved from open flames to laser pixels
Following the short-lived idea of using open flames to light the way, the first electric headlights appeared on the 1912 Cadillac Model 30 and, by the next decade, were quickly becoming mandatory equipment across the nation. The first split-intensity headlights offering separate low and high beams were produced in 1915 but wouldn’t be included in a vehicle’s OEM design until in 1924 and the floor-mounted switch that controlled them wouldn’t be invented until three years after that — a full decade of having to get out of the car just to turn your lights on and blink between brightnesses!
The advent of sealed beam headlights with filaments for both low and high beams in 1954, and its widespread adoption by 1957, proved a massive technological leap. With low beams for dusk and evening driving, and high beams for late night travel on otherwise unlit roads, these new headlights would drastically extend the hours of day a car could safely be on the road.
The first halogen light, which would itself quickly become a global standard, debuted in 1962. But halogens at that time were about as popular in the US as the metric system — we still preferred tungsten incandescents. That changed with the passage of the Motor Vehicle Safety Act of 1966 and the formation of the National Highway Transportation Authority (the NHTSA) in 1968, which took the existing hodge-podge of state-level vehicular regulations and federalized them, as well as the formal adoption that year of Federal Motor Vehicle Safety Standard (FMVSS) 108, which dictated that all headlights be constructed of sealed beams.
By the 1970s, halogen bulbs, with their increased brightness and efficiency compared to tungsten incandescents, became the industry standard. The ‘80s, in turn, saw US regulations expand to allow for replaceable-bulb headlamps, which the European market had already been enjoying for a number of years. The ability to swap out a bulb rather than an entire headlight unit, combined with recent material advances that saw lamp lenses constructed out of plastic instead of glass, drastically reduced the cost of making and operating headlights. And by the ‘90s, halogens had themselves fallen to the wayside in favor of modern xenon and LED lighting technologies. The 21st century has seen further advances to not just the lighting technology itself — hello halo and laser headlights! — but also the control systems that direct the beams.
Due to differences in their relative transportation regulations, the rate of technological adoption has diverged between US drivers and their European counterparts — often with the Americans lagging behind. As with replaceable bulbs in the ‘50s and glare reduction efforts in the ‘30s, Europe has shown itself far more willing to innovate and readily implement recent headlight advances, in part to restrictions imposed by FMVSS 108. Because Standard 108 defined headlights as only having high or low beams — and legally requiring they remain separate — it tacitly excluded all of the technical advances that followed, specifically adaptive driving beam (ADB) headlight systems as found in Audi’s matrix LEDs, Lexus’ Blade Scan LEDs or Ford’s Adaptive Front Lighting System, none of which you will currently find operable Stateside.
Those and similar ADB systems have been available in the Europe, Canada and Japan since the technology's debut in 2004 (though, technically, the 1967 Citroen DS did also feature headlights that swivel in sync with the steering). It would be more than a decade — not until Toyota’s monumental 2015 petition — before the NHTSA would even consider allowing their use in the North American market. In fact, it took another three years beyond that for the agency’s bureaucratic skullduggery to wrap up and it wasn’t until February of this year — a year and a half ahead of schedule because they had to satisfy a requirement set forth in the Bipartisan Infrastructure Bill — that the NHTSA amended the regulation.
“NHTSA prioritizes the safety of everyone on our nation’s roads, whether they are inside or outside a vehicle. New technologies can help advance that mission,” Dr. Steven Cliff, NHTSA’s Deputy Administrator, said in a February press release. “NHTSA is issuing this final rule to help improve safety and protect vulnerable road users.”
“Adaptive driving beam headlight systems, or ADB, use automatic headlight beam switching technology to shine less light on occupied areas of the road and more light on unoccupied areas,” the NHTSA further explained. “The adaptive beam is particularly useful for distance illumination of pedestrians, animals, and objects without reducing the visibility of drivers in other vehicles.”
How Adaptive Driving Beams bend light around rain
Broadly, ADB are headlights that actively adapt to the prevailing weather conditions such as redirecting light around falling rain and snow, extending them ahead of turns or dimming the high beams towards oncoming vehicles only. These systems often leverage the same forward-facing cameras used by the adaptive cruise control system and can be programmed to not just illuminate the road ahead but display prescient navigation information as well.
Audi outside of the US, for example, offers Digital matrix LED headlights — LEDs arrayed in a grid pattern and granularly controlled by a central processor called a DMD (digital micromirror device). They operate much like the digital projection technology they’re based on.
”At its heart is a small chip containing one million micromirrors, each of whose edge length measures just a few hundredths of a millimeter,” Audi’s Lighting page explains. ”With the help of electrostatic fields, each individual micromirror can be tilted up to 5,000 times per second. Depending on the setting, the LED light is either directed via the lenses onto the road or is absorbed in order to mask out areas of the light beam.”
Those masked areas are where the light isn’t bouncing off falling water or glaring into the eyes of other drivers. What’s more, the system will project “dynamic leaving- and coming-home animations” onto nearby surfaces, as a treat. More practically, the system can angle the beams to illuminate farther into turns.
Similarly, the HD Matrix LED system found on later model year A8s, under specific circumstances, will dim the vehicle’s high beams without any human intervention. When the headlights are set to Automatic, the vehicle is going over 18 mph outside of urban areas (as dictated by the navigation system), and the front camera sees another vehicle, the headlights will darken and dim individual LEDs in 64 stages — roughly several million potential patterns — to “mask out other vehicles while continuing to fully illuminate the zones between and adjacent to them.”
Ford’s high-resolution Adaptive Front Lighting System, which debuted in Europe this past August, offers similar capabilities. The company notes that roughly 40 percent of accidents occur on UK roads after sundown. Glancing down at bright infotainment displays while on dark roads can temporarily blind drivers, so Ford’s headlights will project speed limits, navigation cues and road hazard warnings onto the road itself. What’s more, the beams can “bend” around corners and penetrate fog, rain and other inclement weather conditions.
“What started as playing around with a projector light and a blank wall could take lighting technologies to a whole new level,” Ford engineer Lars Junker said in a press release. “There’s the potential now to do so much more than simply illuminate the road ahead, to help reduce the stress involved in driving at night. The driver could get essential information without ever needing to take their eyes off the road.”
Mercedes’ Digital Light system, on the other hand, uses a unique light module consisting of three LEDs mounted in each headlamp. Their light is reflected by a thumbnail-sized array of some 1.3 million micromirrors, each of which is controlled via an onboard graphics processor to precisely bend and attenuate the beams. According to Mercedes, that fidelity enables its Highbeam Assist to function two magnitudes more precisely in excluding oncoming traffic than conventional 84-pixel arrays.
At the other end of the spectrum, Lexus’ Blade Scan high-definition headlights, which debuted in Asian markets in 2019, only utilize 24 LEDs per headlight. Rather than an array of micromirrors, Lexus uses a pair of rapidly-rotating mirrors to direct their light through the lens and onto the road. Per the company, this allows the system to aim with 0.7 degrees of accuracy and detect pedestrians at the roadside up to 184 feet away.
Unfortunately, for as cool as these capabilities are and as technically legal as they are, American drivers still have a short wait before they come stateside. That's because the NHTSA must now devise a set of testing requirements by which to measure and regulate adaptive headlights under the revised standard. In the short term, it means we’ll likely see more new vehicles equipped with ADB-capable-but-disabled hardware that can be activated over-the-air later on, once the regulations have firmed up.
“While adaptive headlights have been approved, the testing requirements for approval put forth by NHTSA is still under discussion,” an Audi representative told Engadget. “Because of this, [I’m] afraid we are still not able to offer the matrix functionality in the US at this time and continue to work with regulators to bring this safety relevant function to market.”