Gotta love technology. Researchers at the Military University of Technology in Poland have come up with a laser-based device that can measure blood-alcohol levels through a car window. It is the same technology, referred to as standoff detection, the military uses to find weapons, hazardous materials and explosives and where lasers and optical techniques are of critical importance for their ability to passively and actively probe threats near and far. Standoff detection can take place at distances from several centimeters up to a kilometer.
How does it work? According to an article in Smithsonian.com:
A laser emitter and receiver sit on one side of the road, while a mirror sits on the other. As a car passes, the emitter sends a laser beam through the vehicle’s window and bounces it off the mirror. The beam is sent at a wavelength that can be absorbed by any alcohol vapor—so, any power loss equates to the presence of booze in the car. If there is no alcohol, there is no absorption. The higher the concentration of the alcohol inside the car, the lower the power measured, because the beam is absorbed by the alcohol.
This laser technology could make checkpoints a thing of the past. But first, there are a few legal hurdles to overcome, including securing a ruling on whether the technology can meet the reasonable doubt test officers must have to pull over a suspected drunk driver. Researchers of the technology must also fix challenging bugs in the system, for example the device giving a false alarm if only the passenger is drunk, and failing to give a reading if the window is open.