This St. Patrick’s Day, San Diego police brought a new device to their DUI checkpoints, one that is able to detect whether an individual has used marijuana or other drugs. The Dräger DrugTest 5000 uses a mouth swab to detect the presence of marijuana, cocaine, opiates, methamphetamine, amphetamine, methadone and benzodiazepines. Dräger began selling the machine in 2009, and it has since been used by police departments across the US, as well as in Australia, Germany, and Belgium.

If a cop suspects a driver of being impaired, he can request that the driver perform sobriety tests or use the Dräger machine. However, unlike the alcohol Breathalyzer, the Dräger cannot test how intoxicated a driver is. If the result is positive, the officer must send the driver to a police phlebotomist to determine the actual blood levels of the drug.

When a person uses marijuana, inactive THC compounds remain in the body for weeks. For this reason, traditional urine tests are ineffective at determining whether a driver was stoned at the specific time of an accident. The Dräger tests only for delta-9 THC, the component responsible for the high, which only stays in a user’s system for a few hours. Therefore someone who legally consumed marijuana the night before they got tested would safely test negative, while someone who was actually stoned while driving would test positive.

“It’s a huge concern of ours with the legalization of marijuana that we’re going to see an increase in impaired drugged driving,” Police Chief Shelley Zimmerman said. The police chief reported that Colorado has seen an increase in drugged driving since legalization, and noted that the numbers are rising in California as well. 38% of all drivers killed in motor vehicle accidents tested positive for drugs in 2014, up from 32% in 2013.

“We want to get these impaired drivers off the streets,” Zimmerman concluded.