Headlight lenses used on modern cars are made of plastic, not glass. Due to UV and other contaminants on the roadway, you must repair a plastic headlight lens once it becomes hazy or cloudy. Repairing the plastic headlight lens is much more cost effective than replacing the lens. Replacing a lens could cost hundreds of dollars. For a fraction of the cost, you can buff the haze out of the headlight and make it look brand new again.
Clean any bug tar, dirt or grease off the plastic headlight with soapy water and then wipe the headlight dry with a clean towel. Starting with a clean surface means you will not introduce any contaminates into the buffing compound that could cause scratches in the plastic lens of the headlight.
Cover the metal edges around the headlight with blue painter's tape to prevent getting buffing compound on the paint of your car.
Place a small amount of automotive buffing compound like, Mothers Plastic Polish, Meguiar's PlastX or DuPont Polishing Compound onto the surface of the headlight. You can find polishing compounds at auto part retailers.
Buff the headlight in small circular motions using a buffing wheel designed to fit a cordless or electric hand drill.
Wipe the surface clean with soapy water every few minutes to remove compound build up.
Complete steps 3 through 5 until the headlight appears clear again.