Headlights, being at the front of the car and covered in clear plastic (except the Roadster) suffer badly
over time from micro abrasion from high speed dust particles. They also pick up chips, scratches and
suffer from UV damage from the light of the sun and also from the light produced from the bulb.

Over time, the headlight plastic becomes less and less clear. This reduces light
transmission making your headlights less bright. It also makes your car look shit.



Plastic Polish

There are several clear plastic polishes for sale, many are sold specifically for headlight plastic lenses.
I bought Meguiar's Plast-Rx (which is called Plast-X in most other countries).

I didn't want to polish the lights by hand so I used a Sealey 75mm polishing ball.
Other companies make similar polishing balls but this one was cheap and goes into a standard drill.



Clean the headlight, apply a good layer of the polish, smear it around and place the polishing ball in your drill.



Use a fairly high speed and keep moving. You don't want to allow heat to build up in 1 area.
Wear goggles or other eye protection as this stuff flies everywhere.  It's like a bukkake film.



After only 1 minute of polishing, these lights looked so much better.

Some corrosion and cloudiness may take longer with a few more applications of polish.
If you have a deeper scratch, you may want to try Displex as shown here.

Just Headlights?

No, you can use it on rear lights if you want but the main other use on the smart is the plastic rear quarter
windows found on the fortwo 450 and Roadster as these suffer from micro abrasion and scratches also.