By John Borland
MIT Technology Review
August 7, 2007

For all their good intentions, drunk-driving rules worldwide have a single, tragic flaw: the drunk drivers they're meant to deter are often too intoxicated to care about consequences.

A growing number of car makers are now turning to high-tech tools to address this fact, creating automotive systems that can keep a car from starting or warn a driver to pay attention if a night of drinking has dulled his or her common sense.

The latest and most ambitious of these in-car sobriety checks comes from Nissan, which unveiled a new demonstration car late last week in Japan. The demonstration offers a full suite of monitoring systems, ranging from cameras that recognize drooping eyelids to stick-shift sensors that measure alcohol content in sweat. All systems are aimed at automatically determining whether a driver is safe for the road.

Like most other such in-car systems, Nissan's experiment isn't yet slated for production-line vehicles. But the demonstration offers new possibilities to policy makers looking for ways to crack down on drunk-driving fatalities, and it has won kudos from road-safety activists such as Mothers Against Drunk Driving (MADD).

"In the area of drunk driving, as with seat belts, there will always be some attempts to subvert [rules]," says Clarence Ditlow, executive director of the Center for Auto Safety, a group based in Washington, DC, and founded by Consumers Union and Ralph Nader. "We think the automatic systems make the most sense in the long run."

Like a friend taking away a drinker's keys, Nissan's demonstration technology attempts to measure blood alcohol content as a first line of defense.

In the concept car, a sensor built into the transmission shift knob reads blood alcohol levels from perspiration on the driver's palm. If that level is above a predetermined amount, the system automatically locks the car's transmission, preventing the car from moving. The company has yet to decide whether a driver should be allowed to override the transmission locks and, if so, how this should be done.

Japanese law sets the legal limit for driving at 0.15 milligrams of alcohol per liter of air in a Breathalyzer (potentially the equivalent of drinking as little as one beer, say experts in Japan). However, the sensors used in the concept car can detect as little as one one-hundredth of this amount, and the threshold set would likely vary by country, says Nissan spokesman Terry Steeden.

Additional sensors placed in the driver's side and passenger's side seat belts, as well as in the back seat, sample ambient alcohol levels in the air of the car, similarly translating that into blood alcohol content. If the threshold level is detected from air samples, the system triggers a voice warning and a message on the car's navigation display window. However, in this case, the car would still start, in part because the alcohol content in the air could be influenced by the number of passengers.

None of these sensors is foolproof. The company is still researching factors that might give false positives or otherwise confused readings, such as foreign substances on a driver's palm, air flow in the car's cabin, or temperature shifts, Steeden says.

Once the car is on the road, a camera mounted on the steering wheel monitors the driver's face, looking for signs that he or she is dozing off.

This system, developed by Nissan in conjunction with unidentified partners, uses facial-recognition technology that identifies a broad range of features--eyes, nose, mouth, and so on--before focusing on the eyes. A calibration tool learns an individual's patterns of opening and closing his or her eyes, turning this into what Nissan calls a closed-eye ratio. Because of the wide variation from individual to individual, blinking is excluded from this ratio, Steeden says.

If a driver's eyelids begin to droop, closing for longer than the normal ratio would predict, the system triggers the audio and navigation-screen warning, and it tightens the driver's seat belt in an attempt to gain his or her attention.

This system, too, has its weaknesses. The recognition system today works only if the eyes are clearly visible, which means that sunglasses, glasses with reflecting surfaces, or even thick frames that obscure the eyes could disable the tool, Steeden says.

Finally, a third set of tools monitors driving activity. External cameras paired with image-recognition software that identifies lane markings on the road are already employed in some Nissan models as a lane-departure warning system. The concept car uses this, along with steering-wheel position sensors, to detect erratic driving behavior.

As with the facial-recognition technology, abnormal behavior such as veering in and out of lanes will trigger the audio and navigation display screen warnings, and the seat belt will again tighten slightly to attract the driver's attention.

As yet, the company has no immediate plans to make these tools, demonstrated last week inside an otherwise ordinary Fuga sedan (known as the Infiniti M45 in the United States), available to consumers.

"This system is a concept, and there is no confirmation of if or when it may be used on future production vehicles," Steeden says. "It is, however, a subject of discussion currently being undertaken by government officials and JAMA [the Japanese Automobile Manufacturers' Association] in Japan."

Nissan's concept car goes well beyond what most other car makers have announced, but the industry as a whole is looking hard at this kind of automatic system.

Volvo has developed a "multilock" system that requires a driver to blow into a Breathalyzer in the seat belt and then buckle up before the car will start. Saab is testing an "AlcoKey" tool--essentially a mini-Breathalyzer about the size of a small mobile phone--that would transmit an electronic signal to the car, allowing it to be started.

Some U.S. states have already begun to require people convicted of driving under the influence to install Breathalyzers, called ignition interlock devices, that can prevent a car from starting following a test that reveals high blood alcohol content.