A 57-year-old Dane County woman was arrested Saturday evening on suspicion of a fourth-offense operating while intoxicated after a traffic stop on southbound I-39/90/94 near DeForest, Wisconsin State Patrol said. A trooper from the agency’s DeForest Post spotted the vehicle being driven unsafely shortly after 5:30 p.m. and pulled it over near mile marker 126, authorities said. The trooper reported observing signs of impairment. After the woman completed standardized field sobriety tests, she was arrested on suspicion of OWI. The woman was being held in the Dane County Jail. An arrest is an allegation, and the information provided did not indicate that she had been formally charged in court.