An engineering team at the Fort Worth, Texas, school has developed an electronic technique that enables policemen to identify drunk drivers among passing motorists remotely. The technique not only provides probable cause for law enforcement agents to pull over impaired drivers, it also gives society a means to deal with an epidemic that kills thousands of people every year. The technology is also expected to be well-received by automakers concerned over liability claims caused by drunk-driving accidents.

"For a long time, law enforcement agencies have been asking for a drunk-driving technology that would give them the equivalent of a radar gun," said Ed Kolesar, Moncrief professor of engineering at Texas Christian University. "This would eliminate the need for law enforcement to do random stops as a means of catching drunk drivers."

Developed by engineering students working under Kolesar, the technique is totally unobtrusive and does not require drivers to blow into a tube or respond to visual prompts. Instead, it uses a tiny ethyl alcohol fuel cell sensor manufactured by PAS Systems International (Fredericksburg, Va.) to monitor air in the vehicle cabin for the presence of ethanol vapor concentrations.

Working with a sampling pump that draws in cabin air, the fuel cell chemically converts ethanol vapors to acetic acid, then produces an electrical voltage output signal proportional to the gas concentration. An op-amp circuit amplifies the raw output signal and a comparator circuit evaluates the data and "decides" whether the driver's blood alcohol level is too high.

If it is, the comparator circuit sends out a signal that drives a 433-MHz Linx Corp. wireless transmitter, which establishes a wireless communication link with a receiver located in a police car.

"If a policeman in the area has a receiver that's tuned to the right frequency, he receives information from passing cars about whether each one is above or below the limit" for driving under the influence, Kolesar said. The signal could also carry additional data, such as a vehicle identification number, thus enabling officers to pick the offending vehicle out of a crowd, Kolesar said.

By placing coupling probes around the vehicle, including in the dashboard, near the steering column and in the headliner, Kolesar said the system can measure blood alcohol concentrations as low as 0.02 percent, at distances of up to 18 inches.

To bring the project to fruition, Texas Christian engineers are working with civil engineers from the University of Texas at Arlington (UTA) and legal experts from Texas Southern University. UTA engineers are road-testing the technology, while experts at Texas Southern examine legal transportation issues. Two undergraduate students from Texas Christian — Tracy Haverty and Kris Shuman — received National Science Foundation funding to carry out the design of the system. The State of Texas Advanced Technology Program Fund also provided funding for the technology.

UTA engineers are currently testing the technology to find out if it can be fooled by perfumes or after-shave lotions, which also contain airborne alcohol molecules. To date, they have tested more than 20 different hair sprays, as well as 60 perfumes and after-shaves, Kolesar said, without triggering a false positive.

Kolesar expects automakers to respond positively to the technology. Potentially, it could help them deal with liability problems, particularly those involving drivers whose judgment is impaired by alcohol at the time of a crash.

Kolesar also believes the cost of the technology would ultimately be low — another plus for automakers. Today's prototype monitors, he said, cost approximately $100 to build, but their cost could be cut dramatically when fuel cells and electronic circuit boards for the device are produced in volume.

If the technology can be successfully brought to volume production, Kolesar expects it to simplify the process of finding drunk drivers. "Today, law enforcement officers look for visual cues — weaving, speeding, failure to stop properly," Kolesar said. "This technology gives them probable cause."