U.S. Lawmakers Give Green Light for Adaptive Driving Beam Headlights
While the technology has existed for years in Canada and Europe, adaptive driving beams (ADBs) have historically been outlawed in the States—until now.
The National Highway Traffic Safety Administration (NHTSA) officially issued a final rule outlining performance standards for America’s “newest” headlamps. What makes the technology so compelling?
Shedding Light on Past ADB Rulings in the U.S.
Despite the U.S.’ lack of exposure to the technology, adaptive driving beams (ADBs) aren’t actually emerging for the first time. In fact, these headlights have been permitted in European vehicles since 2006. Major automakers have historically limited such headlamps to costlier vehicles—treating them as options on upgraded trims as opposed to making them standard.
This has become less common as component prices have slowly fallen. With companies viewing modern safety packages as competitive differentiators, these “convenience” features are becoming more accessible. Automakers are still a long way from making them ubiquitous, however.
An adaptive headlight system. Image used courtesy of Texas Instruments
The regulation outlawing ADBs in the States traces its history back to the 1970s. Lawmakers enacted a high-beam intensity cap on existing headlights—aiming to cut glare on roadways, especially during hours where drivers’ eyes are most sensitive. The technology itself didn’t even reach North America until 2003.
Modern headlamps are much more sophisticated than their predecessors. They function far beyond just emitting light, which has partly led the NHTSA to reconsider its longstanding position.
What Difference Do ADBs Make?
We know that adaptive headlights don’t simply emit light in one fixed direction. Their very name hints at their ability to adjust themselves throughout the course of a drive.
ADBs move on two axes: vertical and horizontal. When the driver turns the steering wheel, the lamps will shift a certain number of degrees in that same direction. This is helpful for navigating curved roadways. Conventional headlights would otherwise “lag” behind the car’s nose and driver’s sightlines—lighting up the shoulder instead of the road ahead. ADBs, therefore, track where you’re heading as opposed to where you’ve been.
The recommended practice ("J3069") from the Society for Automotive Engineers (SAE) on the maximum allowed illuminance of headlamps. Image used courtesy of the NHTSA
Additionally, these bulbs can move upwards and downwards to accommodate changes in slope. Drivers descending or especially climbing hills will experience more optimal illumination. Each beam of light would otherwise face skyward. Oncoming vehicles also benefit. Adaptive headlights dim themselves or adjust their output angle to avoid blinding other drivers, as is the case with Audi’s Digital Matrix LED headlights, for example.
One can imagine how integral visibility is to roadway safety, hence why the NHTSA has approved ADBs. Secretary of Transportation Pete Buttigieg signed the approval nearly one-and-a-half years ahead of schedule; the deadline would’ve extended through 2024. The Biden Administration’s infrastructure bill then enabled the ruling. Additionally, Toyota—America’s top-selling automaker in 2021—has petitioned for adaptive headlights since 2013.
Boosting Road Safety—With a Brightness Caveat
There are major incentives to allow adaptive headlights nationwide. The Insurance Institute for Highway Safety (IIHS) claims that headlights rated “good” can reduce nighttime crash odds by 20%. Just 29% of vehicles had headlights rated accordingly last year. ADBs could help boost that figure. There were also nearly 32,000 recorded traffic deaths in just nine months last year, according to AP.
The IIHS includes an "acceptable and good headlights standard" to its criteria for top safety. Image used courtesy of the IIHS
Adaptive headlights must reduce glare, according to the NHTSA. The ruling also stipulates an “illuminance limit” based on range and lux. ADBs can only project a certain amount of light onto the roadway at any given time. There are other limits and brightness ratios enforced between low beams and high beams. It’s worth noting that an ADB doesn’t have to perform perfectly to gain acceptance. There are times when glare can briefly (legally) exceed limits imposed by the Administration. Automakers do have some leeway.
Evaluating Adaptive Headlight Circuitry
Camera sensors and the vehicle’s computerized systems help determine how these smart headlights distribute light. When the vehicle senses another approaching, it will examine which portions of the roadway are dark and which are illuminated by the oncoming car. ADBs automatically lower light intensity and redirect that output where it’s needed most. This happens without driver intervention.
Audi specifically uses an array of LEDs that determine where light is cast. The company has been able to test and implement different lighting patterns to suit changing conditions. Generally speaking, here’s what standard adaptive headlights require to function:
- High-powered LED drivers to regulate current and brightness
- Switching controllers for thermal management, boost voltage regulation, and buck current regulation
- Matrix manager to control dynamic beam shaping
- Electronic control unit (ECU)
The Key Role of LED Design
LEDs are universally desired due to the granular output controls engineers can achieve. It’s relatively easy to vary the intensity of each individual pixel—ranging from completely inactive to maximum brightness. The structural flexibility of LEDs allows engineers to arrange matrices for optimal lighting performance.
LEDs are energy efficient in mobile, battery-powered devices. Given a host of supporting internals, like those mentioned above, automakers can replicate those benefits in their vehicles. This might become especially important with the shift to EVs and AVs over the next decade. In that respect, it’s suggested that onboard sensors and even LiDAR units might help vehicle headlamps adjust themselves more intelligently.
Accordingly, the pixel board is essential within the headlight assembly. It houses the matrix manager and is cabled to the ECU via a wiring harness. Component manufacturers like Texas Instruments are hard at work to reduce harness sizing—as new adaptive components grow even more sophisticated.
Suppliers like Samsung take a non-traditional approach to LED design. The company’s PixCell array is constructed via wafer, instead of going pixel by pixel.
Samsung's PixCell LED. Image used courtesy of Samsung
An entire LED wafer is cut out and affixed directly to the circuit board. This results in closer spacing and fewer dead zones across the headlight. At a spacing of just 25 micrometers, Samsung’s solution is nearly three times more compact than other discrete LED layouts. Light trespasses less readily and contrast ratios are higher.
The Future of ADBs is Bright
Overall, ADBs can leverage both a matrix mode for dynamic responsiveness and a static mode. The latter acts like a traditional headlight setup. This mode might be most useful during daylight hours when brightness control isn’t so critical.
The future of ADBs is bright; with the U.S. market now open for business, automakers will be more motivated to invest in smarter headlight technologies. The NHTSA’s ruling supports a safer future behind the wheel. How suppliers choose to further innovate LED technology and pixel boards remains to be seen.