Travelers heading south on Interstate 5 were backed up for about an hour at Sutherlin on Wednesday afternoon after a truck jacknifed and struck another vehicle. State Police Trooper Daniel Wells said the accident was one of two which appeared to have been caused by a traffic slowdown as drivers paused to look at a car that had caught fire. The car on fire was stopped on the side of the road near Milepost 132 at about 2:10 p.m. About five minutes later, two crashes occurred. In the first, a freight truck attempting to stop because of the congestion jacknifed. …