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 Vehicle
Subjected to Two Impacts A driver traveling at excessive
speed lost control of his automobile in a curve of the road.
The vehicle crossed over the centerline and collided head-on
with a pickup truck. Soon after, a tanker truck approached
the scene, was unable to stop, and collided with the rear
of the automobile. Damage to the automobile was severe, and
the front-seat passenger was fatally injured. Our client wanted
to know whether the fatal injuries were due to the frontal
impact with the pickup or the rear impact by the tanker truck.
Exponent's engineers analyzed the impacts, passenger's injuries,
and motions of the passenger due to the two impacts. We concluded
that the fatal injuries were caused by the automobile's frontal
impact with the pickup truck and the passenger's improper
use of the seatbelt, not by the rear impact by the tanker
truck.
 Loss
of Vehicle Control The driver of an airport baggage tug
lost control of the tug and the 12,000-lb. train of trailers
he was pulling. The tug jackknifed, and the driver's leg was
pinned between the tug and a trailer. Exponent investigated
the accident to assess the driver's actions, traction characteristics
of the wet pavement, and possible deficiencies of the tug
itself. Our engineers created detailed computer simulations
and discovered that the driver was driving at twice the speed
limit with his leg hanging outside of the tug and had applied
the brakes too aggresively. These factors caused the loss
of control, jackknifing of the vehicle, and injury to the
driver.
 Excessive
Speed or Lack of Visibility? An electrical utility truck
driving on a rural road crashed into a wash-out ditch across
the road approximately 5 to 8 feet wide and several feet deep,
injuring both the driver and passenger. Few photographs were
taken of the accident scene, and rains had significantly altered
the landscape, leaving no physical evidence of the accident.
Exponent was asked to determine the speed of the vehicle and
whether the driver could have seen the ditch in time to avoid
the accident. Using photogrammetry techniques, we determined
the location of the road washout and the tire marks made by
the braking truck. Combining this information with witness
testimony and an analysis of the vehicle damage, we concluded
that the accident could have been avoided if the driver had
been traveling at the speed limit.
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