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Study Illuminates Limitations of U.S. Headlights
Tests by AAA show halogen headlights, which are equipped on more than 80% of vehicles on the road in the U.S., fail to safely illuminate unlit roadways at speeds as low as 40 mph.
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Tests by AAA show halogen headlights, which are equipped on more than 80% of vehicles on the road in the U.S., fail to safely illuminate unlit roadways at speeds as low as 40 mph.
The shortcomings may prevent drivers from seeing a pedestrian, animal or another object or obstacle in time to react and come to a complete stop, according to AAA, which conducted the tests with the Automobile Club of Southern California's Automotive Research Center.
Rural roads and other streets without overhead lighting account for 40% of vehicle miles traveled per year in the U.S. The tests measured the distances at which headlights illuminate non-reflective objects on both low- and high-beam settings. Results compare halogen, high-intensity-discharge (HID) and light-emitting-diode (LED) headlights.
Turning on the high-beams improved sight distances by 28% for cars with halogen lights at AAA's testing facility. But real-world conditions may provide only enough light to safely stop at speeds no higher than 48 mph, the non-profit travel and insurance organization cautions. It notes that only one-third of Americans say they regularly use their high beams.
More advanced HID and LED systems illuminated dark roadways 25% farther than halogen systems during AAA's tests, but most still fall 60% short of full daylight conditions.
AAA says part of the problem is that current U.S. regulations limit light output for headlamps. The organization advocates less restrictive regulations similar to current European rules.
Another concern is that the protective coating used on the plastics of current headlight lenses deteriorates and clouds after about five years, reducing light output and increasing glare for other drivers.
AAA's tests found that restoring lenses doubles the maximum light intensity and reduces light scatter by as much as 60%, thus improving nighttime visibility and minimizing glare for oncoming traffic. But AAA says only one in five motorists in the U.S. has performed this upgrade.