Washington state police are dealing with more drivers impaired by marijuana since its recreational use was legalized last year, and B.C. is preparing for similar problems as a new federal government prepares to follow suit.

Chief John Batiste of the Washington State Patrol visited Victoria this week to take part in an annual cross-border crime forum. He acknowledged that it's a problem since the state legalized marijuana sales to adults in 2014.

"We are seeing an uptick in incidents on our roadways related to folks driving under the influence of marijuana and drugs in general," Batiste told reporters after a meeting with B.C. Justice Minister Suzanne Anton.

He explained the state's new law setting a limit for marijuana's active ingredient in blood, similar to the blood-alcohol limit. But without a roadside testing device, police are relying on training from the State Patrol's drug recognition expert to make arrests.

What they need now is a roadside testing device that provides evidence of impairment that will hold up in court, Batiste said.

Prime Minister-designate Justin Trudeau made a high-profile promise to legalize marijuana before winning a majority government Oct. 19.

In B.C., police can charge drivers if they show signs of impairment, whether from drugs or fatigue. In alcohol use cases, drivers are typically charged with impaired driving and driving with a blood alcohol content of more than .08 per cent.

Vancouver-based Cannabix Technologies is developing such a device. The company issued a statement Wednesday, noting that Trudeau has promised to begin work on legalizing marijuana "right away" and a reliable method of enforcement is needed across North America.

The company says it is developing a hand-held device that can detect marijuana use within the past two hours. Saliva and urine tests can come up positive for marijuana "long after intoxication has worn off," the company stated.