It’s a cold and rainy winter night. Your headlamp beams drill a tunnel of light into the gloom of a deserted country lane. Unfortunately, it’s not a very deep or bright tunnel. You have to slow the car to a crawl, otherwise you’ll overdrive the headlights. But it’s not a pea-soup-thick fog that’s causing the problem. So why can’t you see farther than a couple of car lengths ahead of your vehicle? Once safely home and parked, you leave the headlights on and walk to the front of your car, fully expecting that one of your low beams has burned out. Wrong. They’re both lit—but a closer inspection reveals that the lenses of your headlamp assemblies are frosted over. And it’s not just dirt. The plastic lens itself is as cloudy as a bathroom mirror right after a shower. No wonder you can’t see.