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 ...