Many fatal "accidents" occur when a motorcar strikes a bridge abutment. The most prevalent type of accident on the Interstate Highway System is the single-vehicle accident, in which the vehicle strikes a fixed roadside object or overturns. Currently the most effective protection is placing plastic barrels, partially filled with dry sand, in front of the impact surface. This is more effective than current guard rails. Many, if not most, bridge abutments do not even have guard rails. Further, it is recommended that the base of bridge abutments and central piers facing the roadway be of the same configuration as the General Motors bridge parapet, an adaptation of the New Jersey, concrete median barrier. Current European practice uses pre-stressed and post-tensioned concrete beams or box units 600-700 feet long, thus allowing placing abutments over 100 feet from the right side of the roadway, and eliminating the center pier, even when 150-foot medians are provided.