You've seen it repeatedly. You're driving down the highway on a warm, sunny day, and you spot a dog in another car, lolling out the open window. The dog's ears flap in the breeze, and the expression on its face suggests that sticking its nose in the wind is just heaven.

Still, there's something about this sight that raises a couple of questions. Why do dogs love this so much? And, isn't this not only distracting to the driver and possibly even kind of dangerous?

Well, first you have to remember that the canine nose is much more sensitive than those found in the middle of the human face, their sense of smell is so much more developed. Consider the canine nose. While the human nose has about 5 million aroma receptors embedded in a piece of nasal tissue the size of a postage stamp, some dogs have more than 200 million receptors in a sheet of tissue folded inside their noses. At the back of each dog's mouth is an extra olfactory organ which is connected to the nasal cavity by air ducts. The organ seems to give dogs the ability to more precisely distinguish among odors. Think of it as an olfactory turbocharger, and the part of the canine brain dedicated to processing data from the nose is enlarged.

Having established the superiority of the canine nose, the next question involves the safety of allowing dogs to drape their noses outside the car window. Obviously, sudden stops or a crash could cause serious injury to your dog, but the problem goes beyond that.

The main problem can involve ear and eye infections. There's also the chance that the dog could get a bug or flying debris in the eye, which could do some damage at 55 or more m.p.h.

As for safety, there are a wide range of restraint systems available, including crating, but the protection varies greatly. The simplest systems involve a simple tether, like a leash connected to the dog's collar on one end and to the seat belt on the other. These do a good job of keeping dogs from exploring areas where they don't belong. This kind of system, however, provides relatively little protection during an accident, when a sudden impact could turn the dog into a four-legged yo-yo. What might be better is a restraint system using a harness instead of a collar. And a dog should never, never be simply deposited in the bed of a moving truck. Know your dog and what can distract or excite him in a car. Then spend some time exploring the options; crating, harnesses or restraint systems that will ensure his safety.