Drafting

On the freeway, I regularly see cars following a semi truck way too closely - I assume they're trying to take advantage of improved fuel efficiency that drafting allows.

(Drafting is where the leading goose, bicycle, vehicle takes the brunt of breaking through the air, making it easier for nearby followers.)

Of course, drafting behind a truck is dangerous - I'd rather pay more for gas than risk ending up under a truck - and we've all seen how often a moronic driver will cut in front of a semi.

So why can't we create our own drafting? Short of designing cars as if they're aircraft, is there no way to break the wall of air up into a mini-wake? Even a small improvement would add up over the course of a year - I drive about 80 miles per day, most of it freeway. (Yes, I would love to own a more efficient vehicle - say, a diesel that runs on cooking oil.)

Perhaps some aerodynamic, vertical fins on the front bumper, perhaps extending onto the hood - that way, you'd be slicing into the air, rather than shoving it aside.

How about a magnetic field that would create a virtual nose-cone for your vehicle? Just how strong would a magnetic field have to be to nudge atmosphere in an efficient way at highway speeds, without requiring magnets so heavy you're canceling out any benefit? Maybe something for Mythbusters to test out - they had a good piece on drafting a while back.