An ARCCA expert was called to investigate an incident in which an extended cab pickup truck rolled over negotiating a highway off ramp with three occupants inside.  The driver was ejected, the left rear occupant was uninjured, and the right front occupant received life threatening injuries when she was crushed by the collapsing roof.

Steps Taken:

  • ARCCA’s expert performed a vehicle inspection, including a full forensic examination of the seat belts.
  • The airbag control module was downloaded with the CDR tool.
  • The expert reviewed the police report, including scene diagrams taken with Total Station.
  • The expert reviewed all police and media photographs.
  • The expert performed a site inspection, scene diagram and scene measurements and then scanned the scene using a Faro 3D laser scanner.

Final Findings:

Based on the site inspection, police report, and photographs, the truck was attempting to negotiate the highway off ramp at a speed too fast for the design of the ramp.  The tire marks revealed that the truck was reaching critical yaw speed when it left the ramp.  The truck then tipped over as a result of centripetal acceleration, as well as the grade and slope of the hill adjacent to the unpaved shoulder bordering the ramp.  The truck then rolled at least one time, ejecting the driver, who turned out to be unbelted, along the path of the roll out. The forensics also revealed that the left rear occupant and the right front occupant were both wearing their respective seat belts.

The Electronic Data Recorder (EDR) contained no deployment events, as the truck was not equipped with rollover airbags, and the rollover did not result in any decelerations in the forward to aft direction that would enable the airbag control logic.  As a result, no pre-incident or pre-crash data was recorded.

Pre-incident speed was calculated from the Critical Yaw Speed formula along with the energy required to roll the truck.  The truck was further reviewed for crashworthiness issues relating to the roof crush and how it affected the seat-belted passenger.

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