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As the voting season is nearing and more states are considering marijuana legalization for the use of marijuana on the November ballot, Stanford University engineers are attempting to resolve one continued concern: how law enforcement can keep impaired drivers off the road. Is there an accurate marijuana test to show the level of intoxication of impaired drivers?

A group headed by Stanford professor Shan Wang invented a portable device that can detect THC molecules in saliva. Drivers involved in crashes with higher levels of THC in their blood are three to seven times more likely to be responsible for the incident than drivers who are not under the influence, the National Institute on Drug Abuse reportsStudies show that those who smoke at least an entire joint can be impaired while driving.

Officers who suspect or observe marijuana intoxication can use a cotton swab to wipe the inside of a driver’s mouth, test it in the new device (called a potalyzer) and get results viewable on a smartphone or laptop within three minutes, according to a Stanford news release.  For now, officials rely on marijuana tests: blood, breath or urine tests that aren’t always 100% accurate. Saliva tests exist as well, however they’re also not completely accurate either.

Tom Abate, associate director of communications at Stanford Engineering, said he does not know how this particular test will compare to others that are currently on the market, but Stanford’s potalyzer does measure the presence of THC and concentration.

Stanford’s new potalyzer device can show THC within the range of 0 to 50 nanograms per milliliter of saliva, within most measurements of impairment, the release states. Colorado law says drivers with five nanograms of active THC in their blood can be prosecuted.

Beyond marijuana detection, the biosensor chip in the potalyzer device could also be used to test other drugs, including heroin and cocaine, the release says.

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