WALTHAM, Mass. » An alcohol-detection prototype that uses automatic sensors to instantly gauge a driver’s fitness to be on the road has the potential to save thousands of lives, but could be as long as a decade away from everyday use in cars, federal officials and researchers said Friday.

U.S. Transportation Secretary Ray LaHood visited QinetiQ North America, a Waltham, Mass.-based research and development facility, for the first public demonstration of systems that could measure whether a motorist has a blood alcohol content at or above the legal limit of .08 and — if so — prevent the vehicle from starting.

The technology is being designed as unobtrusive, unlike current alcohol ignition interlock systems often mandated by judges for convicted drunken drivers. Those require operators to blow into a breath-testing device before the car can operate.

The Driver Alcohol Detection Systems for Safety, as the new approach is called, would use sensors that would measure blood alcohol content in one of two possible ways: either by analyzing a driver’s breath or through the skin, using sophisticated touch-based sensors placed strategically on steering wheels and door locks, for example.

Both methods eliminate the need for drivers to take any extra steps, and those who are sober would not be delayed in getting on the road, researchers said.

The technology is "another arrow in our automotive safety quiver," said LaHood, who emphasized the system was envisioned as optional equipment in future cars and voluntary for auto manufacturers.

David Strickland, head of the National Highway Traffic Safety Administration, also attended the demonstration and estimated the technology could prevent as many as 9,000 fatal alcohol-related crashes a year in the U.S., though he also acknowledged that it was still in its early testing stages and might not be commercially available for 8-10 years.

The systems would not be employed unless they are "seamless, unobtrusive and unfailingly accurate," Strickland said.

The initial $10 million research program is funded jointly by NHTSA and the Automotive Coalition for Traffic Safety, an industry group representing many of the world’s car makers.

Critics, such as Sarah Longwell of the American Beverage Institute, a restaurant trade association, doubt if the technology could ever be perfected to the point that it would be fully reliable and not stop some completely sober people from driving.

"Even if the technology is 99.9 percent reliable, that’s still tens of thousands of cars that won’t start every day," said Longwell. Her group also questions whether an .08 limit would actually be high enough to stop all drunken drivers, since blood alcohol content can rise in people during a trip depending on factors such as how recently they drank and how much they ate.

"It’s going to eliminate the ability of people to have a glass of wine with dinner or a beer at a ball game and then drive home, something that is perfectly safe and currently legal in all 50 states," she said.

LaHood disputed that the technology would interfere with moderate social drinking, and said the threshold in cars would never be set below the legal limit.

In Friday’s demonstration, a woman in her 20s weighing about 120 pounds drank two, 1 1/2 ounce glasses of vodka and orange juice about 30 minutes apart, eating some cheese and crackers in between to simulate a typical social setting, said Bud Zaouk, director of transportation safety and security for QinetiQ.

Using both the touch-based and breath-based prototypes, the woman registered a .06 blood alcohol content, Zaouk said, so she would be able to start the car.

Laura Dean Mooney, president of Mothers Against Drunk Driving, said the technology could "turn cars into the cure."

While she did not foresee the alcohol detection system ever being mandated by the government, Mooney, whose husband died in an accident caused by a drunken driver 19 years ago, said she could envision it someday becoming as ubiquitous as air bags or anti-lock brakes in today’s cars, particularly if insurance companies provide incentives for drivers to use those systems by discounting premiums.