For most people, cars confer a kind of invisibility. Admit it--when you're behind the wheel, you probably do things that you wouldn't otherwise dream of doing outside the privacy of your own home. You might sing loud and off-key to the radio, talk to yourself, make faces, clean your teeth or curse at strangers.

Most of us think of our cars as cozy, intimate spaces--even though we're sitting in the middle of a public thoroughfare and surrounded by glass.

But if you believe that you have any privacy behind the wheel, think again. Nowadays, a variety of high-tech devices may be watching you at any given moment. Radar, lasers and cameras may be taking electronic "snapshots" to enforce traffic laws. The navigation and emergency-notification system in your vehicle has a global positioning system that can theoretically keep track of every move you make. Ditto your E-ZPass tag, which automatically registers where and when you drive through a tollbooth. And if you drive a vehicle made within the past 10 years, you may even have a "black box" hidden away on board, digitally recording your speed, braking and other driving data.

The very existence of a black box in your car may come as a surprise to you. And it raises a host of questions. How does it work? Exactly what data does it collect? Who has access to the data? All of those questions imply a larger one--do you, as a motorist, have any expectation of privacy behind the wheel these days?

Inside the Box
Automotive black boxes have their roots in aviation. Used for decades, the famous black boxes on airliners--formally known as flight data recorders (FDRs) and actually colored bright orange--continuously register the status of components, controls and pilot inputs. A separate system, the cockpit voice recorder, saves pilots' conversations. Both have proved invaluable for investigating crashes, training flight crews and designing safer airplanes.

Borrowing the terminology as well as the technology, automotive engineers call their black boxes "event data recorders" (EDRs). They're usually silver, small enough to fit in the palm of your hand, and they don't record voices. They do, however, continuously monitor the status of various controls, and they record the readings in a five-second "loop." For example, the simplest EDRs can reveal the vehicle speed, engine speed, acceleration, throttle position, brake status, airbag deployment timing and safety belt usage for the five seconds immediately before a crash. The most sophisticated EDRs can record just about anything electrical on the car, right down to headlights and turn signals.

According to experts, most U.S. automakers have been installing EDRs on at least some of their models since the mid-'90s, and the list is growing. For instance, nearly all new vehicles made by General Motors now come equipped with EDRs; that includes some other brands, such as Isuzu trucks, made by GM. Many Fords have EDRs, too. So far, only a handful of imports have them.

Who Wants to Know?
EDR proponents cite two big reasons for using the technology, and the first is safety. "We think that the use of EDR data on an aggregate level could revolutionize safety research," says David Snyder, vice president and general counsel for the American Insurance Association. "What we learn could take us well beyond this uneasy plateau of 42,000 or 43,000 traffic deaths annually in this country, where we've been stuck for several years. Such research could lead to improved designs and save more lives."

Besides safety, however, insurance companies have a more particular interest in black boxes. "The data from EDRs could be used to settle litigated claims quickly and fairly and to decide which claims ought to be contested," continues Snyder. "Right now, in trying to determine the circumstances of a crash, you often have a battle of experts and eyewitnesses in court."

Obviously, EDRs wouldn't eliminate such court duels entirely. As decades of aviation investigation show, experts often argue over different interpretations of black-box data after a crash. But empirical evidence gathered electronically usually proves more reliable than eyewitnesses. Recently, for example, prosecutors charged a Florida man with vehicular homicide after a head-on collision in which he was involved killed two people. Eyewitnesses claimed that he was "speeding recklessly." But the jury acquitted him after the black box in his Chevy S10 pickup showed that he was traveling 60 mph--not 90 mph, as witnesses had testified.

The Slippery Slope
Despite the potential benefits, privacy advocates have some real concerns about EDRs. "When it comes to their cars, Americans are very sensitive about intrusions," notes Chris Hoofnagel, associate director of the Electronic Privacy Information Center, a Washington, D.C.-based group concerned with the civil-liberty implications of emerging technologies.

For privacy watchdogs, EDRs represent the edge of a slippery slope. So far, courts have ruled that motorists have no expectation of privacy on a public roadway. Such legal reasoning at least partly underpins automated traffic enforcement techniques, such as cameras and radar to catch red-light runners and speeders. (See the related article "Smile! You're on Traffic Camera!").

But Hoofnagel points out a big difference between automated enforcement and black boxes. "Sure, you're out in public where anyone can see you, and a red light camera might snap your picture when you commit a violation, " he says. "But black boxes collect data continuously. These machines are almost beyond human experience. They're on all day, all the time, even though data transfer doesn't occur unless there's a bad event."

That is-for now. The EDRs that come standard on today's passenger vehicles require a hard-wire connection to a device such as a laptop for downloading. And the data stored in the five-second interval before a crash have been used only in limited circumstances-in court, for instance, or by a few safety researchers. But wireless capability is available with current technology. In fact, some trucking companies already use it to manage their over-the-road drivers. How long is a truck in operation? How many times does it exceed a certain speed limit? What's its average speed? The driver's boss can keep tabs from his desk.

Safety researchers practically salivate at the prospect of wireless access. "Currently, the greatest limiting factor for researchers is that EDR data must be downloaded device by device," admits AIA's Snyder. "To be able to download and hold aggregated data at another location-that would significantly improve research capability."

Bootstrapped Snooping
Privacy advocates see things a bit differently. "The problem with EDRs and similar technology is that it's easy to bootstrap them into other uses," says EPIC's Hoofnagel. He cites automated speed enforcement as an analogy. It started out simply as a better way to deter dangerous driving. But some localities quickly recognized its potential for revenue enhancement and began using it to ticket minor violations. "Once you have the technology, it's hard to stop law enforcement from expanding its uses beyond its original purpose," notes Hoofnagel.

In fact, some users have already found other imaginative applications for black-box technology. A few car-rental firms now use vehicle monitoring and global positioning systems to make sure customers abide by their rental contracts--obeying speed limits and staying within state boundaries, for example. And insurance companies have floated the idea of using wireless vehicle monitors to track their policyholders' behind-the-wheel behavior and adjust premiums accordingly. As one recent study from the Georgia Institute of Technology suggests, "Premiums may increase significantly for vehicle activity over 65 mph, accelerations over 8 mph/second, etc." Variable premiums based on policyholder surveillance would "discourage risky driving behavior, " says the report. Progressive Insurance has already test-marketed such a system with volunteer customers in Texas.

Who Gets In?
Obviously, the drivers in the Progressive experiment knew about the monitors in their vehicles. And car-rental customers should read the fine print on their rental agreements, which usually disclose monitoring devices. But what about family cars?

Most experts agree: As the vehicle owner, you own the black box data, unless the fine print in your sales contract specifically excludes it. As part of your personal property, it can be subpoenaed in a lawsuit. Getting to it, however, is another matter. Downloading requires proprietary access codes held closely by automakers.

Currently, the federal government has no regulations governing even the disclosure of EDRs to vehicle owners. This spring, AAA called for strong federal measures to inform consumers and safeguard their privacy, including window stickers to identify vehicles equipped with black boxes. Other consumer groups have recommended a clear-cut "opt-in" system (which would presume a driver's refusal to share EDR info unless specified otherwise) and measures to limit data use and ensure its security after downloading.

In June, the National Highway Traffic Safety Administration (NHTSA) proposed the first federal guidelines for EDRs, including the requirement that owner's manuals contain a paragraph informing consumers of the presence of a black box on their vehicles and explaining its capabilities. The government also wants manufacturers to make EDR data more accessible to crash investigators.

NHTSA stopped short of requiring EDRs on all new vehicles. But clearly government safety experts look forward to eventually compiling a national database--for information about the five seconds leading up to every crash in every car in the country.

"The technology is already there to provide the benefits of aggregate EDR data collection without affecting an individual's privacy," concludes AIA's Snyder. But until the law catches up to technology, many drivers remain uneasy, knowing that Big Brother may be along for the ride.