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Shine On
Bright ideas will help you see and be seen better.
By Paul Abelson
Of all our senses, sight is most important when driving. From the road in front through our windshields, to the road behind through our mirrors, to the condition of our truck through our instruments, vision is our main source of information. In daytime, long-distance vision is more than adequate to alert us to any dangers. At night or in bad weather, we must rely on lighting to assist us.
Until the 1930s, vehicle lighting was poor. It mattered, but perhaps not as much as today, because speeds were limited by loads and available power and rarely exceeded 30 to 40 mph, even between cities. But as cars and trucks grew and became more powerful, the government decided to regulate lighting.
Instead of setting minimum requirements and letting industry meet or exceed them, the old Interstate Commerce Commission (ICC) tested lighting of the day and selected the 7-inch round incandescent sealed lamp, with low- and high-beams, as the best available. These became the only lamps allowed on vehicles. So, while Europe experimented with innovative bulb-and-reflector designs, the U.S. was stuck with 1930s technology for years.
Things changed, eventually. Starting with the 1957 model year, the ICC allowed vehicle makers to split high- and low-beam functions, using paired 4-inch round sealed incandescent bulbs. The reflectors were identical, but each lamp could now have specialized optics in its lens. Then in the early 1970s, after halogen bulbs had proved their superiority all over the world, the young U.S. Department of Transportation finally allowed the use of halogen, but only in sealed lamps of the old design.
After petitioning by car makers, the government allowed rectangular single and double lamps, more to satisfy stylists than engineers. It was only in the early 1980s that the National Highway Transportation Safety Administration (NHTSA) let Lincoln produce the first aerodynamically styled, optically improved bulb-and-reflector halogen light on any U.S. vehicle. Lighting development then accelerated, as engineers sought to meet the performance needed on our Interstate system.
You must first see danger before you can react to it. At 70 mph, a driver with a half-second reaction time needs 100 feet to react after seeing a hazard. He then needs another 200 to 300 feet to stop. Headlights now have a range of only 300 to 350 feet on low beam. With high beam use restricted when other vehicles are present, there isn't much of a safety margin under ideal conditions. Add rain, snow or fog and the margin vanishes. That's why you slow down in bad weather. It's a reaction to the limits of your vision; it's also the law.
Today's lighting engineers are developing many new systems. Here are two that are in use; others will likely come soon:
Halogen: A dozen or so years ago, Volvo introduced an experimental truck with integrated aerodynamic headlights. The reaction among many fleet members was near panic. "Seven-inch round lights work well," they claimed. "They're cheap and easy to replace, and they last long enough." Aerodynamic lights became popular, but now premium Freightliner and Kenworth trucks all have 7-inch round lights. They're no longer sealed incandescents, but sophisticated lamps with replaceable halogen bulbs.
All the integrated shapes, such as those on the Volvo VN series, Peterbilt 387, Freightliner Columbia and Mack Vision, use carefully designed reflector optics and clear lenses to get as even and effective a light pattern as possible. Even Truck-Lite, known for rear and side lighting, has introduced a new aerodynamic integrated headlight-parking-turn signal in a housing that can be used on either side.
High Intensity Discharge (HID): A relatively new lighting system has been introduced on several luxury cars. HID operates like a theater arc-lamp or an aerial searchlight. Electric current is stepped up to extremely high voltage and made to jump, or arc, between two electrodes. The arc glows with a very bright bluish-white light. HID units use only 35 watts each, compared with 55 to 65 watts for a typical halogen. HIDs produce a greater light flux from a narrower point of light, so optics can more easily place light where it's wanted. It was once impossible to have both low- and high-beams in an HID lamp, so separate high beam modules were often employed. Engineers are experimenting with magnetic fields to bend the arc, which may lead to high-, low- and even mid-range beam patterns.
The future: There is a limit to how much light can be sent down the road without blinding other drivers. Instead of more light, engineers are working to improve light patterns, to concentrate light where it's needed. Hella has a multi-filament lamp that adapts to speed and direction. If you turn slowly, more light shines into the turn than ahead. As speed increases, the computer changes the shape and distance of the beam.
General Motors and Ford have been working on infrared sensing devices; GM introduced it first in this year's Cadillac DeVille. A sensor in the grill detects heat differences and projects a picture onto a heads-up display near the base of the windshield. Objects beyond the range of normal lights show up clearly on the display, out to at least 500 feet. That's more than enough time to react to a person, a deer or even the warm exhaust pipe of a stalled vehicle. Others are testing ultraviolet light that causes objects to glow without blinding oncoming drivers.
Distributed lighting uses a central "light engine," a bright light source hidden inside the cab. Light is taken where it's needed by fiber optics, thin strands of glass or special plastics. Fiber optics can project light ahead or use it indirectly on instruments. It can be projected in a narrow or broad beam, so instead of discrete headlight modules, the grill, bumper or some styling feature can double as the sole source of forward lighting.
Cutting the Fog
Stray light is the greatest enemy of visibility in fog, rain and snow. It will reflect into your eyes, reducing visibility. All good fog lights have a horizontal top cut-off so they send light far enough forward to allow driving at reduced speeds, but not upwards where it can dazzle you.
Fog lights should be aimed so the beam drops about four inches every 25 feet. If, for example, the top of the light is 24 inches above the ground, the top line of the beam shined against a wall 25 feet away should be 20 inches up. The beam should never be as high as the top of the lamp.
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