TUMWATER — An impaired motorist drove about 17 miles in the wrong direction on Interstate 5 at speeds as high as 100 mph before troopers stopped her early Wednesday, the Washington State Patrol said.While several drivers reported near-misses, there were no collisions and no injuries.The driver got on the freeway about 2 a.m. Wednesday near Tumwater, heading north in the southbound lanes, Trooper Guy Gill said.Driving at speeds ranging from 38 mph to 100 mph, she evaded several spike strips. Troopers closed the lanes in Tacoma and sent patrol cars down to intercept her, lights flashing and sirens blaring. Gill said the driver finally stopped “bumper to bumper with a patrol car.”Troopers encountered a “calm, 60-year-old female who had no idea where she was,” Gill said. Her statements led troopers to suspect a combination of alcohol and prescription medications might have been involved, he said.Pamela Drawsby of Olympia was arrested for investigation of driving under the influence. The Seattle Times reported she was charged later Wednesday in Thurston County District Court with DUI.Gill said the arrested woman’s blood alcohol reading showed her to be above the .08 legal intoxication threshold in Washington but he didn’t have the exact figure. He said the investigation continues and additional charges are possible.