Illinois law has required back-seat passengers to wear seat belts since 2012.  An Illinois Department of Transportation survey shows nearly 85 percent of the state’s back-seat passengers are buckling up, an increase of 7 percentage points since 2013.  But it’s still a lower rate than the 95 percent wearing seat belts in front seats.  IDOT released the results Friday.  The September survey shows Chicago and Cook County have lower rates of buckled passengers in back seats compared to the state average.  The surveyed Illinois counties of Champaign, Bureau, Effingham, Rock Island, Madison and Saint Clair collectively did well, with 9 out of 10 rear-seat passengers buckled.