The sweater-wearing grandmother drove right through a red light near Frontier Village.

After she was pulled over, she gave police all the warning signals of being a drunken driver. But the breathalyzer test came back negative.

Washington State Patrol Sgt. Harlan Jackson wasn’t persuaded that the woman was clean.

“I’m seeing impairment and seeing signs of stimulant use during the evaluation,” said Jackson, who is a specially trained drug recognition expert.

So troopers took a sample of the woman’s blood. It showed positive for cocaine use and the woman faced charges for driving under the influence, Jackson said.

Beginning today, the Washington Traffic Safety Commission is helping to pay for extra traffic patrols in Snohomish County through Sept. 7.

State officials are using the woman’s case as an example that police now are looking for more than just drunken drivers. They’re also looking for anybody who is taking drugs that might impair their ability to drive safely.

Nationally, nearly 13,000 people were killed by impaired drivers in 2007, and drug or alcohol use by drivers is the leading cause of traffic deaths in Washington, statistics show. Last year, impaired drivers contributed to nearly half of the state’s 522 traffic deaths.

Too often people believe that it’s OK to drive after taking prescription medication, Jackson said.

They ignore warning labels that caution people from operating heavy machinery.

“I’m not going to operate a backhoe or forklift,” people often say, Jackson said.

But cars, which weigh thousands of pounds, are definitely heavy equipment.

Just as people line up a designated driver if they plan to drink alcohol, people should ask someone to drive them if they plan to take some prescription drugs and need to get somewhere, he said.

“Officers are definitely trained to look for signs of drug impairment,” Jackson said. “They are mindful of it and they are looking out for it.”

Jackson Holtz: 425-339-3437, jholtz@heraldnet.com.