Headlights often do not provide an adequate amount of light to illuminate a dark roadway, and when they become cloudy or yellowed, obscuring the bulb, this further reduces light, compounding the dangers of nighttime driving. When used on low beam, headlights that have declined in efficiency provided only about 22 percent of the amount of light new headlights did when operating at full capacity. Signs of deterioration can begin when headlights are only three years old, but most commonly by five years. Replacing headlights with original parts offered the most improvement in the amount of light produced, the report found. Professional and DIY restorations returned light output back to about 70 percent; these were the most cost effective option, but they offered less improvement in light output than replacement, and produced more glare than is considered acceptable.

Source: Forbes December 15, 2018 01:18 UTC