Study: Cloudy Headlights 80% Less Effective

Winter presents a prime opportunity to check and correct headlight cloudiness


DENVER (Dec. 20, 2018) – Are you ready for winter's long nights? Clouded or yellowed headlights generate only 20 percent of the amount of light that new headlights do, per new research from AAA. That leads directly to precarious nighttime driving conditions.

"Clouded headlights are much more than a minor nuisance. They're a real safety issue," said AAA Colorado spokesman Skyler McKinley. "In Colorado, we're lucky to experience so many sunny days each year. The flip side of that coin is the resulting prevalence of headlight deterioration increases the danger on our roads at night."

Ultimately, it's sunlight that causes a car's plastic headlight lens to deteriorate, giving it a clouded or yellowed appearance. AAA examined the impact of deterioration on the amount of light produced using an accredited laboratory to test headlights from two popular sedans, approximately 11 years in age. Results from the degraded headlights were measured against new headlights to quantify the amount of light produced for each. All testing was conducted in accordance with the Federal Motor Vehicle Safety Standard 108 as set forth by the Department of Transportation (DOT).

Replacement and Restoration
Research revealed that deteriorated headlights, when used on low beam, provided just 22 percent of the amount of light a new headlight does when operating at full capacity. AAA also examined the effects that replacing or restoring a headlight can have on improving the amount of light produced. Replacing headlights with original equipment manufacturer parts is the most effective method to restore light output back to 100 percent.

Aftermarket parts also performed well, restoring light output between 83 and 90 percent. Unfortunately, they additionally failed to meet certain requirements for light intensity and were found to be more likely to produce glare for oncoming traffic. Restoring headlights, while the most cost-effective option, offered less of an improvement in light output than replacement. Professional and DIY restoration returned light output back to approximately 70 percent. Both restoration methods, however, produced more glare than is acceptable per DOT criteria.

New Headlights Start Out Subpar
Compounding the difficulties presented by deteriorated headlights is the fact that U.S. headlights start out with significant shortcomings even when new. Previous AAA research  found that halogen headlights fail to safely illuminate unlit roadways at speeds as low as 40 mph, with high beam settings offering only marginal improvements. Even the most advanced headlights tested illuminated just 40 percent of the sight distances that the full light of day provides. By not maintaining headlights, drivers are unknowingly operating in dangerously dim conditions.

"Driving at night with headlights that produce only 20 percent of the light they did when new, which is already subpar, is a risk drivers shouldn't take – and one they certainly shouldn't expose other road users to," McKinley said. "That's especially true when you consider that there are convenient and inexpensive solutions that can dramatically improve lighting performance."

Depending on where and how the vehicle is used, headlights can begin showing signs of deterioration as early as three to five years after they roll off the line. The average age of American cars on the road today is 11.6 years. Unlike batteries or tires, most drivers are not in the habit of routinely inspecting their headlights. AAA suggests drivers check their headlights for changes in appearance such as yellowing or clouding. If the bulb is difficult to see, it is time to have the lenses replaced or restored as soon as possible. 

AAA members can redeem a $5 off instant coupon from NAPA for its 3M headlight lens restoration kit (PN 39008) at Members can print the coupon from the site and redeem at participating NAPA stores through Feb. 28, 2019. 

Headlight assemblies used in testing were for the driver's side of the vehicle. To quantify headlight performance, AAA contracted an accredited testing laboratory with expertise in automotive headlights and conducted testing according to industry standards. Headlights were tested to FMVSS-108 standards with no modifications to the headlight assemblies under test or to the test procedures.

The professional headlight restoration systems used a power-sanding technique to remove the original protective film from the headlight lens. The resulting scratched surface of the polycarbonate was then polished using increasingly finer grades of sanding discs and a protectant film was applied to the entire surface of the headlight lens. Full methodology is available in the research report, found here

About AAA Colorado

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