Grime can reduce headlight effectiveness by as much as what percent?

• A. 70 percent
• B. 50 percent
• C. 90 percent
• D. 30 percent

Answer: (C)

Grime on the headlight lens cuts how well you can see by reducing how much of the light actually gets through to the road. The film and roughness created by dirt absorb and scatter the beam, so the light that should clearly illuminate the road is dimmed and diffused. When grime is heavy, the loss can be extreme, potentially up to about 90 percent of the light output compared with a clean lens. That dramatic drop is why dirty headlights can make nighttime driving much harder and why keeping the lenses clean matters so much. In lighter cases you’d expect smaller reductions, but the possibility of a near-total loss in the worst grime scenarios explains the emphasis on that high figure. Cleaning or restoring the lens can restore much of the lost brightness and improve visibility.