At 11:35 am., e.d.t., on October 7, 1983, a Mack 3-axle tractor, Model No. R685ST, which was pulling an MC306 (AL) cargo truck semitrailer loaded with 8,600 gallons of gasoline, was traveling in the right lane of westbound I-76 (Schuylkill Expressway) in Philadelphia, Pennsylvania, when it veered leftward, crossed the left lane, and collided with a concrete New Jersey-type median barrier. The combination vehicle overturned on the barrier, and gasoline, which spilled from the tank, was ignited. Three eastbound vehicles, which were caught in the area of the fuel spill, subsequently burned. Two persons were fatally injured, and one person was seriously injured. After firefighters arrived onscene and extinguished the fire, smoldering fire caused the reignition and explosion of excess fuel trapped beneath the westbound access ramps. Two firefighters and a news media person were injured during the subsequent explosion. The National Transportation Safety Board determines that the probable cause of this accident was the fatigue induced fracture and separation of the two main leaves on the right bogie leaf spring assembly of the tractor which permitted the right end of the rear bogie axle to rotate rearward and caused the tractor cargo tank semitrailer to steer uncontrollably toward the left. Contributing to the loss of life and injury severity were the rupture of the cargo tank and the ignition of the released gasoline immediately following the impact with the 32-inch-high New Jersey barrier.
Samenvatting