When studying for your first driver's license, you learned three hand signals--left arm up for a right turn, out for a left and down for a stop. Unfortunately, except for the upraised middle finger, those three hand signals are the only gestures with a clear meaning on U.S. roads.

Driver-to-driver communication has made little progress beyond those simple hand motions. Technology has helped, but only a little. We now have turn signals and brake lights to communicate changes in direction and speed, so we don't have to stick out our arms in the rain. But try to convey a message even slightly more complicated--for example, "I'm sorry" or "After you"--and we're at a loss. It's a problem that has plagued drivers since the advent of the hardtop and roll-up windows. How can you end the isolation and frustration you feel inside that metal box on wheels? How can you communicate with others on the road?

Driving in Babel
Any kind of communication relies on established conventions in which some signal--a sound or gesture, for instance--carries a defined meaning, recognized by both the sender and the receiver. Driving has no such conventions. Take flashing headlights, for example. When another driver flashes his headlights, he might be saying, "Turn on your lights." Or he might just as well be saying, "Turn off your lights." Maybe your high beams are on. Maybe one headlight is burned out. Or maybe a speed trap lies in wait up the road. Who knows?

Most gestures are just as ambiguous. A few years ago, the AAA Foundation for Traffic Safety conducted an informal survey on its Web site, asking drivers, "How do you say you're sorry?" Hundreds of respondents gave dozens of variations. Some were clever, such as knocking the heel of one hand against your forehead, in a "wow-I-could've-had-a-V-8" way. Others were well informed but impractical, such as making a circular motion over your heart with a closed fist (American Sign Language for an apology, which is hard to see behind the wheel). No gesture was mentioned by more than 20 percent of the respondents, and most had suggestion rates in single digits. Ironically, this admittedly unscientific attempt to define a common language showed only that we're still driving in Babel.

Europe has made a little more progress. In recent years, drivers there have taken to holding up three fingers of their right hand horizontally, roughly forming the letter "E," for "Excuse me," "Excusez-moi" or "Entschuldigen Sie mich."

"Many people think the gesture might jump the pond and become more widely used over here," says Frank Niland of the Club's Traffic Safety department.

Open for Interpretation
If Americans do begin to adopt the three-fingered "E," it will join a handful of other more-or-less common hand signals you might notice on U.S. roads. None has a clearly defined meaning, but you might see them used by truck drivers and others who spend a lot of time behind the wheel.

• "Happy Talk" Hand. Tapping the thumb and four bunched fingers together rapidly several times like a hand puppet (think of Bloody Mary making "Happy Talk" signs in South Pacific) usually indicates a problem with your lights. Perhaps you've left a blinker on, a taillight is burned out, or you need to turn your headlights on.
• Capital "T." Forming a "T" with two hands (like the traditional "time-out" signal in sports) probably means "Trouble." You can interpret it as the sender's plea for assistance. If accompanied by pointing to a specific spot on the car, it may indicate that you're the one who has trouble--say, a loose wheel, burned-out light or dangerously low tire.
• Thumbs-Down. Like the capital "T," a gladiator-style thumbs-down signal usually means that you have a problem that deserves your attention. Pointing indicates where the problem lies. Conversely, a Top Gun-style thumbs-up may mean "Thank you," "No problem" or "All clear."

Although interpreting these signs can present a problem, using them can be downright dangerous. At worst, other drivers can misinterpret even your most well-intentioned gesture.

"Suppose you mistakenly cut somebody off on the highway, and you flash the peace sign as a way of apologizing," says Niland. "You hold up two fingers, but maybe the guy behind you sees only one. You could end up in an altercation." Add high speeds, tinted windows and night driving to our lack of a common on-the-road sign language, and the opportunities for misinterpreting gestures or missing them altogether seem endless.

Barring a revolutionary advance in communications technology, you're stuck with sticking your arms out the window or flashing hand signals at your own risk.