SEATTLE (AP) — Researchers at Washington State University are working on a breath test to determine if a driver is under the influence of marijuana.

The News Tribune reports that law enforcement officers have a test for alcohol, but they don’t have a tool to test for marijuana impairment. Right now, officers must use blood tests to determine if THC is present in a driver’s blood.

But WSU chemistry professor Herbert Hill says existing technologies like those used by airport security agents to detect drugs and explosives can be altered to test breath for THC. Hill says his team hopes to start testing on humans early next year.

The Washington State Patrol says it welcomes anything that gets impaired drivers off the road.