From the December 2017 issue
From the moment electric headlights snuffed out kerosene and acetylene lamps in the 1910s, automakers have struggled to illuminate the road without blinding oncoming drivers. The industry’s first unified effort to rein in glare was led by the carmakers themselves before the automobile was federally regulated. In the span of just two model years, 1940 and 1941, every new car in the United States adopted standardized seven-inch round headlights. These sealed-beam assemblies, combining the bulb, lens, and reflector into one unit, eventually expanded to include additional sizes and rectangular shapes, but the original seven-incher was still popping up in vehicles such as the 1990–1997 first-generation Mazda MX-5 Miata well after NHTSA had approved replaceable-bulb and nonstandard-shaped headlights in 1983.
Today’s lighting regulations primarily dictate performance, allowing manufacturers to choose from a handful of technologies. High-intensity discharge (HID) lamps produce light with an electric arc in a gas-filled bulb rather than the filament used in conventional halogen bulbs. The latest trends favor energy-efficient light-emitting diodes (LED) and lasers. Both allow for precise control and placement of the beam, to the extent that some “smart” headlights can carve out a dark spot around an oncoming car.
Our test revealed that technology isn’t the only factor in determining headlight performance. NHTSA allows headlights to be located between 22 and 54 inches from the ground yet also calls for a horizontally oriented cutoff to block the beam from angling upward into the eyes of approaching drivers. Mounting the headlights higher, then, is the only way to elevate the beam. That’s exactly why the 1916 Ford Model T Touring we tested did such an admirable job exposing the body of our decoy deer at a distance of 100 feet [see top right] while several of our modern cars threw their light at the deer’s feet. However, the T’s crude reflectors created a narrow spot beam, barely wider than the car itself, and intensity fell off rapidly beyond 100 feet.
The 2018 Honda Fit’s halogen bulbs are hardly an improvement on a 1997 Miata’s sealed-beam lights. And at just 50 feet out from the car, the bright center of the Mercedes E400’s beam passed below our light meter positioned 24 inches off the ground. The 305-hp Dodge Challenger GT AWD can’t spin its own tires, but it was the Hellcat of headlights in our test. Its HID lamps flooded our testing field with the brightest light in each of the eight measurement locations. It helps that the all-wheel-drive Challenger has an SUV’s stance.
Lux quantifies the intensity of light as perceived by the human eye. City streets are typically illuminated to about 10 lux at night while the lights in a living room are roughly equivalent to 50 lux. An overcast day is usually around 1000 lux.
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