Dear Car Talk:
I have been driving for 50 years. Why are there fewer dead insects on my windshield?
Great question, Bill. Assuming it's not just that your vision is shot after 50 years, the answer is aerodynamics. It turns out the effort to improve gas mileage also resulted in fewer squashed bugs, and decreased sales of bug-and-tar remover.
To make a car more efficient, one thing you want to do is reduce wind resistance. Wind resistance is why you can throw a spear farther than you can throw a bedsheet, even through the bedsheet is lighter.
So, nowadays, cars are carefully shaped so they "slip" through the air more easily. Wind-tunnel tests are used to perfect exterior designs so air moves smoothly around the car as the car drives through it, rather than crashing into it and slowing you down.
If you want to see an example, go online and look up a picture of a 1992 Volvo 240. You'll see a big, flat grille in front and an upright, nearly flat windshield. Both are perfect for catching wind and bugs.
And to see what's happened in the 20 years since then, look up its replacement, a 2012 Volvo S60. It's a suppository on wheels, with a pointy front end and a long, gradually sloping windshield and equally sloping rear window. You can see that it's designed kind of like a bullet. The result? The air goes smoothly around it, which minimizes wind resistance and helps improve mileage.
And that air takes the bugs with it. Instead of hitting that big, flat windshield and meeting their bug-maker, the bugs get carried in the laminar flow right over the car and deposited on the other end. Often shaking their little bug heads and saying, "What the heck was that, Frank?"