If you wear glasses to correct your vision, chances are good you already know the benefits of polycarbonate lenses over glass ones. Not only are polycarbonate lenses significantly lighter, they’re also much more impact-resistant than glass.

Polycarbonate windows have been used in racing cars for years to shed pounds, and the time may be right to roll out plastic windows in production cars, too. As The Detroit News tells us, Fiat’s 2014 500L will join more exotic offerings (like the Porsche 911 GT3 and the Audi R8 GT) in using plastic for some of its glazing.

Auto glass typically weighs around 100 pounds, but polycarbonate windows can cut that figure in half. These days, every pound counts, so switching to plastic for the fixed rear windows and sunroof panels becomes an easy way to shed weight.

If plastic side windows are good enough for race cars, why not deploy them on production cars as well? The short answer is safety, since polycarbonate is too flexible and too impact resistant. First responders would have a difficult time breaking plastic windows, especially compared to the ease at which they can shatter glass windows.

In other words, current safety regulations prohibit the use of polycarbonate in door windows and windshields, since plastic windows increase the risk of injury to unbelted passengers (since they don’t shatter), while upping the complexity of rescue or escape from a burning or sinking vehicle.

Questions remain on polycarbonate’s scratch and haze resistance as well. Headlight housings have been made of polycarbonate for years, but headlights scratch and yellow over time.

To counter hazing, manufacturers could add a UV-blocking layer, though this doesn’t address the scratching issue. The other potential stumbling block is cost, since polycarbonate windows can be twice as expensive as their glass equivalents.

That will likely change as demand for plastic windows increases and the production numbers rise. Fiat may be among the first automakers to embrace the idea, but Ford is just about done with its own polycarbonate window testing. Plastic rear windows could appear on the next Ford Transit Connect van.

As automakers look to boost fuel economy in any way they car, such evolutionary steps are unavoidable. As to whether or not plastic is a viable replacement material for glass in auto glazing, we’ll find out over the next decade.