Analysis by Daniel Stern, DVN Chief Editor
At great long last, NHTSA are publishing a Final Rule amending Federal Motor Vehicle Safety Standard № 108 to permit ADB. The agency, ordered by the U.S. Congress to get a move-on about it, chose a 2013 Toyota petition as the nominal basis for the amendment; the final rule can be downloaded directly from NHTSA here. It is a 327-page document, the first 272 pages of which are discussion of NHTSA’s decisions regarding what to permit, what to require, what to forbid, and generally how to configure the ADB regulation.
There was reason for optimism when the infrastructure bill (now law) instructed NHTSA, in plain language, to allow ADB in accord with SAE J3069. Nevertheless, in the final rule NHTSA have gone to great length (pages 22-27) to assert that this black-letter directive from the U.S. Congress didn’t actually mean NHTSA had to permit ADB in accord with SAE J3069. Instead, they have issued a rule of their own making. It incorporates some elements of J3069, but with many departures, and some of NHTSA’s seemingly self-contradictory decisions will likely inspire a great deal of discussion amongst the community of engineers who now must live with the new regulation.
NHTSA’s specifications appear to deliberately maintain the century-old constraints of the seeing-versus-glare tradeoffs that ADB technology is intended to resolve. The NHTSA rule requires that the de-glared zones must comply with low beam minimum intensity requirements; for example, if an ADB-equipped vehicle headed up a hill detects a vehicle ahead at (1.5°D, 2°R) relative to the ADB-equipped vehicle, the ADB system must still direct at least 15,000 candela toward that vehicle ahead—thus offering no glare relief relative to static low beams. NHTSA states (page 80, footnote) that they “decided not to require additional glare protection performance from ADB systems beyond that currently produced by lower beams“, yet on page 241 they state “in the absence of empirical evidence to the contrary, the agency still believes that glare poses a non-trivial safety risk“.
This looks like a cancellation of one of ADB’s two principal advantages over static beams, and it’s puzzling in at least two ways: on the one hand, it is a decision made by the agency on the receiving end of headlight glare complaints that have been steadily increasing for many years. On the other hand, it is an explicit statement that NHTSA does not regard low-beam glare as problematic—which becomes even more baffling in context of their decision to continue imposing the high beam axial intensity limit of 75,000 candela per side of the car, which is just under 34 per cent of the intensity allowed in the rest of the world.
By sticking with this high beam intensity limit set in 1978, most of half a century ago, they’ve passed up the opportunity to give drivers much-needed increased light. On pages 194 to 197, NHTSA acknowledge more light would likely address the increasing numbers of pedestrians hit in traffic, but the risk of glare from higher intensity, they say, is unacceptable. Research on the matter has consistently concluded safety would best be served if the US high beam intensity limit were raised. Yet NHTSA have consistently swatted away petitions seeking an intensity rise, on grounds that the US limit, set in 1978 based on research carried out with sealed beam headlamps, is best even though it “may not be as intense as some manufacturers might think that their customers might desire“. This current final rule again fails to raise the high beam intensity limit ostensibly on glare concerns, despite the fact that the whole point of an ADB system is to automatically, dependably, and dynamically keep glare out of other road users’ eyes, thus removing the busy, sometimes careless, sometimes malicious human driver from that process.
In sum, then, NHTSA—having declared that glare is a safety threat—have ruled that low beam glare is not an issue worth addressing with ADB technology that can reduce it without affecting seeing, but high beam glare is a dangerous risk that must be avoided by hobbling ADB technology that has demonstrated, over 16 years and uncountable millions of vehicle-kilometres travelled, its ability to safely control high intensity even in glare-averse Europe. This looks like a cancellation of the other of ADB’s two principal advantages over static beams. It will have to suffice, NHTSA says on page 197, that ADB systems will “increase upper beam use, which will help prevent crashes“. Effectively, then, the NHTSA rule permits ADB as long as it is constrained by the limits imposed by the old seeing-versus-glare tradeoffs of old-fashioned static low and high beams.
Moreover, the ruling leaves the problems of headlamp aim unaddressed, and imposes new costs. ADB really requires that headlamps be horizontally aimable—find previous DVN discussion of that matter here and here—yet NHTSA contend that visual/optical horizontal aim of a low beam is unacceptable because it is impossible to provide a suitable kink or other beam feature without “damaging” the beam pattern. The ruling also refuses to accept a special aim mode, providing a visual/optical reference (a vertical line, for example) not provided during normal operation of the lamps.
Instead, a horizontal VHAD will be required. For those who don’t remember them, VHADs were devices briefly used in the early 1990s. They were scale-and-pointer arrangements meant to indicate when the headlamp—the physical hardware itself—was pointed straight ahead, without any direct reference to the light beam. VHADs were quickly and uniformly found to be unreliable, problematic, and expensive, and they drove the push toward visual/optical aiming in the mid-1990s. NHTSA’s new ADB ruling flatly says “are too!” to the fact that VHADs are not reliable (page 143).
And on page 144, a claim is made that allowing horizontal aimability without a VHAD, in accord with rest-of-world practice, could “limit the potential for innovative safety solutions generally afforded by this final rule“. That’s an assertion likely to raise eyebrows and hackles among those who have been watching, from front-row seats (not to mention driver’s seats) as ADB systems in the rest of the world have been providing well-demonstrated safety benefits for 16 years and millions of vehicle-kilometres—all without VHADs. On pages 231-232 of the ruling, NHTSA present a large list of commenters to the long-ago NPRM, who described how and why the agency’s proposed in-house rule, by its disharmony with UN and SAE standards, would drive up costs and slow down ADB in the U.S. market. And on pages 234-236, NHTSA dismisses these comments—”NHTSA is not persuaded…NHTSA believes…NHTSA concludes“—then, on pages 240-241, NHTSA acknowledge their rule will cost more to comply with than SAE J3069.
The test protocol for ADB, as specified in the ruling, requires specific headlamps and taillights on the test fixtures: 2018 Ford F-150 and 2018 Toyota Camry headlamp and taillight, and 2018 Harley-Davidson motorcycle headlamp and taillight. These, like all other car lights, will eventually go out of production—in fact, the Harley-Davidson headlamp originally specified already went out of production while NHTSA were writing this rule. NHTSA assert (page 96) they imagine later-year headlamps will be substituted by some future amendment to the regulation, but the agency’s track record suggests this could well turn into a problematically outdated aspect of FMVSS № 108.
For many decades, philosophical differences drove divergence between U.S. headlamps and European (at first; eventually rest-of-world) headlamps: in Europe, glare was not tolerated and so European low beams minimised glare at the cost of short seeing distance. In the U.S., the opposite approach held: seeing distance was maximised at the cost of glare. These were not right or wrong answers; they were different points on a continuum of trade-offs and constraints imposed by the limitations of static beam patterns. By artificially retaining these obsolete constraints, though, NHTSA’s ruling appears to guarantee that U.S. drivers will continue to be deprived of the seeing improvements and glare reductions available in every other country on the planet, as ADB systems in the rest of the world can reduce glare and increase seeing to a much greater degree than what NHTSA have just specified.
