This document provides biographical information about Gary M. Johnson and summarizes an accident reconstruction he performed of a 2002 GMC Sierra truck. It details that a 79-year-old male driver lost control on an interstate onramp, struck a barrier, and then a tree, which resulted in his death. Data was retrieved from the vehicle that showed it was traveling about 23 mph at impact and information collected was used to simulate the crash in LS-Dyna software to compare the simulated damage to the actual vehicle damage.

1. Gary M. Johnson

2. 6 Years USN, Submarine Nuclear Propulsion

Plant Operator – Mechanical
Bachelors in Criminal Justice – Auburn

University 1995
Auburn Police Department 1994-1999

Investigated @1500 crashes

Private Accident Reconstruction Since 1999

Reconstructed an additional 1100 crashes

Attending UAB since Fall 2002 (Graduate

School prerequisites and Graduate School)

3. Pole (and tree) impacts represent special

problems to safety systems
The narrow cross section of the pole

concentrates the vehicles’ energy in a small
region
The vehicles speed does not change rapidly

until there is significant engagement “fooling”
most airbag deployment algorithms

4. Some vehicles are equipped with

discriminating sensors that change the
algorithm when engaged
These sensors usually mounted near the

middle of the radiator
This still leaves the areas outside of the frame

rails (or equivalent) unmonitored

6. February 2, 2004

Light Rain

79 year old male driver

2002 GMC Sierra 1500

Interstate 20/59 just south of Interstate 459

onramp

7. The driver lost control and struck the “Jersey

Barrier” with the left front and left rear corners
of the vehicle

8. It then traveled in an arc across the southbound

lanes
Left the road near 45 degrees to the road

Went through a silt fence

Struck a tree with the left front of the vehicle


11. Due to impact with barrier and clockwise yaw

of the vehicle, driver was out of position
against the drivers’ side window at impact
with the tree
Driver was wearing his seat belt

Airbag did not deploy

Driver was killed


15. Retrieval equipment currently only manufactured

by Bosch
Covers some GM vehicles back to 1994

Also later models of Ford, Chrysler, Suzuki,

Sterling, Isuzu, Mitsubishi, and Saab
Comprised of software, interface box, power

supplies and (currently) 21 different cables

16. This particular vehicle stores 5 seconds of pre

“impact”
Speed

 Throttle position
 Engine speed
 Brake switch circuit status
Change in velocity up to 150 milliseconds and

maximum delta v
Drivers seat belt switch status

Ignition switch cycles at event

Stores non deployment events as well as

deployment events

18. This is
longitudinal
change in
velocity

21. Speed at impact of about 23 miles per hour

Recorded longitudinal delta v was 19.22 miles

per hour
Driver was out of position against the drivers

door due to a combination of the lateral impact
with the barrier and the clockwise yaw into the
tree

22. LS-Dyna is a general multiphysics simulation

software package developed by the Livermore
Software Technology Corporation
Non Linear

Ideal for

 Changing boundary conditions
 Large deformations

23. Command line driven

Vehicle model –Chevrolet C1500 – from George

Washington University National Crash
Analysis Center Laboratory
Used the reduced model with 10,500 elements


24. Converted to a key file using Hypermesh

Added x plane and tree

Tree was not rigid cylinder but used density,

modulus and Poisson's ratio of white oak

25. Purpose was to compare physical damage to

vehicle to simulated damage
Crash truck was extended cab, simulated truck

was regular cab
Not an issue, just looking at damage forward of the

firewall
Initial speed of 23 miles per hour

Input units are mm/sec, this converts to 10,277

mm/sec

29. Tire/ground plane friction was too low, this

exaggerated the restitution
No cab intrusion or damage to door surface

Hood angle is similar, but bent in a different

location (hood catch and latch were broken)
Vehicle had struck the barrier with the left

front prior to the impact with the tree

30. Contact information:
Gary M. Johnson
Vear, Inc.
1500 1st Ave North
Suite R-127
Birmingham, AL 35203
W 205.307.6543
C 205.427.2250
gjohnson@vearexperts.com