A Washougal woman died in a single-vehicle accident on Interstate 84 in Sherman County on Tuesday afternoon.  The Oregon State Police says 52-year-old Vickie McDowell was a passenger and sustained fatal injuries in the accident.  According to the OSP, a preliminary investigation showed a van driven by 45-year-old Shannon Gatlin of Camas was westbound on I-84 near milepost 110 when it traveled into the median and rolled several times.  Gatlin was taken to Mid-Columbia Medical Center for serious injuries.  The OSP says the crash occurred at about 4:05 p.m. Tuesday.  The OSP was assisted by Sherman County Sheriff’s Office, Sherman County Ambulance, North Sherman Fire and Rescue, and the Oregon Department of Transportation.