Beer-breaths beware. A new concept car with breathalyzer-like detection systems may provide even greater traction for Japanese efforts to keep impaired drivers off the road.

Nissan's alcohol-detection sensors check odor, sweat and driver awareness, issuing a voice alert from the navigation system and locking up the ignition if necessary.

Odor sensors on the driver and passenger seats read alcohol levels, while a detector in the gear-shift knob measures the perspiration of the driver's palm when starting the car.

Other carmakers with detection systems include Sweden's Volvo, which has developed technology in which drivers blow into a measuring unit in the seat belt before an engine can start.

But Nissan's car includes a mounted camera that monitors alertness by eye scan, ringing bells and issuing a voice message in Japanese or English if a driver should pull over and rest.

The car technology is still in development, but general manager Kazuhiro Doi says the combination of detection systems will ultimately keep an eye on who's behind the wheel.

We've placed odor detectors and a sweat sensor on the gear shift, but for example if the gear-shift sensor was bypassed by a passenger using it instead of the driver, the facial recognition system would be used, said Doi.

Also keeping a short leash on drivers, car seat belts tighten if drowsiness is detected, while an on-road monitor checks if a car is keeping its lane properly.

Japan's No. 3 carmaker has no specific timetable for marketing, but aims to yoke all technology to cut the number of fatalities involving its vehicles to half 1995 levels by 2015.

Nissan's Doi says they still have to distil exactly what impairment means: If you drink one beer, it's going to register, so we need to study what's the appropriate level for the system to activate.