The windows in your car are an important piece of equipment, designed not just to let you see outside, but also to protect you from bugs, wind, small rocks, and other things.

While the windows have many important jobs, the most essential one is to let you see your surroundings so that you can safely drive. With that in mind, many people might ask why cars come with a bunch of lines on the rear window.

While small, those lines make it slightly more difficult to see, which you would think is a bad thing. In reality, however, they serve a very important purpose.

The lines are actually the rear defroster. For your front window, your vehicle takes air that is heated by the engine (or from a heating element in electric vehicles) and blows it onto the window, causing any snow to melt or fog to evaporate away.

It would be less efficient to create a system of ducts to take the warm air all the way to the back, especially since it is most needed when the car is first started, and the engine is not yet up to temperature. So, car makers have developed a simple system that is very effective.

They place wires onto the rear window (or, more commonly in modern vehicles, placed in between two pieces of glass). When you turn on your rear defroster, electricity is sent through the wires, and the resistance creates heat. That heat will quickly melt any snow, ice, or fog away.

In most cases, you will actually find that the rear windows get cleared off much more quickly than the front. This is for two reasons.

First, the heating elements are able to get up to temperature almost immediately, which does not happen for the engine. Second, the rear window is usually more vertical than the front windshield, so any snow or ice can slide off more easily.

Unfortunately, while the small wires going across the back window don’t cause any major issues when it comes to seeing, they would be a problem in the front, which is why they are not added there.

And now you know why rear windows in vehicles have stripes!

If you thought that was interesting, you might like to read about 50 amazing finds on Google Earth.