Visibility

Drivers depend on visual cues for 90 percent of their responses. When darkness falls or bad weather hits, vision, depth perception, and color recognition are compromised. The result can be deadly: Traffic deaths are three times more common at night than during the day.

Headlights, therefore, are one of a car's most important safety features. But despite advances in headlight technology, driving at night isn't as safe as it could be, because the solution is also the problem.

The challenge for safe night driving, then, is for drivers to be sure their vehicles provide sufficient light to see far enough ahead but not so much light that it creates a problem for other drivers. At the same time, drivers need to find ways to protect themselves from glare created by other vehicles.

Glare comes from a variety of sources, including:

High-intensity-discharge headlights: HID headlights, introduced on U.S. cars a decade ago, are available today on an increasing number of vehicles. They produce about 2.5 times the light of conventional halogen bulbs. A motorist using HID headlights can see about 330 feet ahead, compared with about 190 feet for halogen lighting. But many motorists complain that HID headlights create hazardous glare for oncoming drivers.

High-mounted headlights: Headlights on many SUVs and pickups are mounted as much as nine inches higher than car headlights. Also, "lifted" SUVs and pickup trucks, which have become popular recently, have suspensions that can elevate them an extra couple of feet above the pavement. These vehicles' headlights often shine directly into oncoming motorists' eyes or into rearview and sideview mirrors.

Specialized lighting: More motorists are using auxiliary driving lights and spotlights on their vehicles. Some of these devices are intended for off-road use only. When used on the road, such lights often become a source of glare.

Misadjusted/misused headlights: Some studies show that half the vehicles on the road have at least one misadjusted headlight, which can create glare if it shines into the eyes of oncoming drivers. Also, drivers using their car's high beams too close to other vehicles create glare.

Dirty headlights and windows: Dirt on car headlights and windows scatters light, increasing glare.

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