A new invention may soon make it easier for police who pull over risky drivers to test them for marijuana impairment on the spot, in addition to the usual alcohol breath test.

A marijuana breathalyzer will begin clinical trials early next year, the Oakland, California-based Hound Labs Inc. announced this week.

"The idea is that law enforcement will have one device out on the road to test for both THC [a marijuana component] and alcohol," said Hound Labs CEO and founder Dr. Mike Lynn, an emergency room physician at Highland Hospital, in Oakland.

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Typically, measuring the level of tetrahydrocannabinol (THC) -- the psychoactive component in cannabis that gives users a "high" -- is done using urine, blood, or saliva tests. The results can show if marijuana has been used in recent days or weeks, but they are not a very accurate way to measure real-time impairment, said Lynn.

Hound Labs has been collaborating with scientists at UC Berkeley to develop the technology.

"The UC Berkeley scientists are a really good group, including the chair of bioengineering and the associate dean of the college of chemistry. It's a complicated scientific challenge," Lynn told CBS News.

The handheld device will be tested for roadside use by law enforcement agencies in the San Francisco Bay Area and then Lynn hopes it will eventually be used across the country.

"We plan to do clinical studies and also work with law enforcement on testing to make sure we have the exact device that's really needed out there on street," he said.

The AP reported in July that researchers from Washington State University also have a portable marijuana breathalyzer in the works.

Under that state's Initiative 502, which voters approved to legalize recreational marijuana use in 2012, drivers are considered impaired if they test positive for at least 5 nanograms of THC per milliliter of blood.

But Lynn, who is also a reserve deputy sheriff for Alameda County, California, said standards for marijuana impairment out there right now are sketchy. He hopes the availability of breathalyzers will shift the national dialogue from one focused on detecting if THC is in the body to a discussion about creating standards that reflect actual impairment.

Sales of Hound Labs' devices to police and consumers could begin late next year, he said, and could carry a price tag of $1,000 or less.

About 20 million Americans use marijuana, and as more states legalize it, some studies have found it's becoming more common for young people to drive stoned than drive drunk.

"From a trauma center perspective, I have seen the terrible, senseless tragedies related to impaired driving," Lynn said. He's seen it from a law enforcement perspective, too, and knows the challenges police officers face when dealing with impaired drivers.

"When I started the company, it was my intention of finding a way to measure this stuff in breath. Every single death or injury from an impaired driver is preventable and there aren't many things in life like that that are preventable," he said.