(Vancouver, WA)  --  Alcohol is believed to be a factor in a head-on crash that injured half a dozen people in Clark County.  The Clark County Sheriff's Office says they've arrested 23-year-old Tyler Campbell of Vancouver on charges of vehicular assault for the crash Saturday morning in Brush Prairie.  Police say Campbell may have been intoxicated when he crossed into oncoming traffic on Northeast Rawson Road, striking a car head-on.  Campbell's car then rolled onto its side, prompting a third vehicle to crash into it.  Six people were hospitalized.