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Accident Reconstruction and Failure
Analysis
This is a brief description of the
services available, to you. Each of the following sections is
approached in a unique way. The italicized words at the end of
each title give a clue as to how each service is presented. For
a detailed table listing equipment and issues from previous work
experience, refer to the bottom of the Curriculum Vitae in a
section titled ACCIDENT RECONSTRUCTION ACTIVITIES.
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Effort has been made to make it interesting and informative and
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![[Bullet]](images/bullet.gif) Quality and
Customer Orientation-
Human Factors Analysis
- Transportation,
Traffic and Highway Engineering Specialties
- Cost Effective
Services and Timely Responses
An accident is an unfortunate
event. Each accident is a unique event. Yet there are methods
of investigation and analysis common to many of these events.
These commonalties, which we know generally and collectively
as mathematics and physics, allow the engineer to study and
analyze the hard and soft evidence and make determinations
about what happened before, during and immediately after the
accident event.
GILLENgineering personnel
have, over the past 20 years, investigated and analyzed
hundreds of accidents involving passenger cars, trucks,
motorcycles, trains, bicycles, pedestrians, as well as many
unique conveyances such as electric peoplemovers, high-rail
rail vehicles, etc. Accident reconstruction activities have included, among others,
daytime/nighttime visibility, vehicle handling, lighting,
roadway design and markings, signalized intersections, etc.
Through specialized
engineering knowledge and skills in surveying and photogrammetry, GILLENgineering personnel have been
significantly involved in an even wider range of accident
reconstruction activities. Included are catastrophic power
plant infrastructure failures, hurricane damage assessment,
flooding and residential foundation/basement stability.
These activities require the
skilled use of many tools, both computer related and
otherwise. GILLENgineering maintains up-to-date software,
hardware and equipment to perform detailed assessment and
analysis required in the understanding of failures and
accidents.
The following descriptions
provide you with an introduction to the types of engineering
services available at GILLENgineering. For additional
information or to discuss your unique failure event, make
contact via phone, fax or mail through the Contact Section of
the HOME
PAGE or by E-mail
through the FEEDBACK page.
- Traffic Accident
Reconstruction: Some Tools
What do you think of when you
hear the phrase "traffic accident": two vehicles
colliding head on or at an intersection, a car slamming into
a tree or pole, multiple vehicles piling up on a foggy
mountain pass, a car being struck broadside by a train at a
grade crossing? These are the events that make the news
headlines. They often involve fatalities or serious injury.
The most important thing to understand about such an event is
"What caused it." When the collective causation
modes of traffic accidents are accurately understood,
measures can be taken to reduce both the numbers and severity
of traffic accident related deaths, injuries and damages.
-
- In addition to the
"headliner" type accidents, there are also a
myriad of other safety related traffic events which cause
damage or injury. Examples include a low-speed collision
in a parking lot or where stopped vehicles are queued at
a stop light, a bicyclist is knocked down while
traversing the edge of a traveled way, a vehicle
unexplainably veers off the road. If highway, vehicles
and operators are all functioning correctly, these things
should not happen. But they do happen, and all too often.
Finding out what went wrong and how an accident happened
is the job of an accident reconstructionist.
Vehicle Dynamics
At GILLENgineering we use many
tools to solve these problems. First and foremost are the
basic underpinnings of Newtonian physics dealing with motion
and forces. Newton's Laws tell us how things work, at least
here on our earth based reference system, as regards mass,
force and acceleration. The dynamic events of a traffic
accident must subscribe to these laws and through application
of the laws and sufficient known information about an
accident much can be learned about the events during and
leading up to the accident.
We look at the accident
dynamics and select the appropriate tools or equations to
solve the problem of "How and Why did THIS
Accident Happen." In one case it would be appropriate to
employ the critical speed formula to determine the minimum
speed above which a turning vehicle would break lateral
traction and slide off a curve. In another case, flip and
vault calculations would be required to calculate the speed
of a vehicle at the time it slid sideways into a curb and
went airborne. Yet another case would need the use of the
fall equation to determine the speed of a vehicle at the time
it went airborne, without being tripped. These equations are
all derived from the basic fundamental laws of Newtonian
physics, and have been adapted for use in accident
reconstruction.
To cost-effectively understand
the pre-accident conditions, such as speed at initial impact
(and the associated Delta-V, or speed at the secondary
impact) GILLENgineering utilizes EDCRASH, written and sold by Engineering
Dynamics Corporation (EDC), a known and recognized name in
the field of accident reconstruction software.
EDCRASH is used
to calculate Delta-V from either one, or both, of two
sets of inputs: crush data and/or impact and rest
locations. The crush data approach compares the actual
crush data on the subject vehicle or vehicles to known
conditions resulting from crash testing required by NHTSA. Crush stiffness coefficients
determined from the crash test vehicles are applied to
the subject car for the specific location and amount of
the damage measured on the accident vehicle. The
Principle Direction of Force (PDOF) and vehicle weight
are input along with a set of initial conditions. EDCRASH
then calculates the Delta-V, or change in velocity
experienced by the occupant compartment portion of the
accident vehicle. This is important for the biomechanical
analysis of a vehicular accident because Delta-V
correlates strongly with the speed of contact of an
occupant with the inside surface of a vehicle, thus the
speed associated with an occupants injury.
The momentum
approach, useful for non-linear collisions (those other
than head-on or rear-end collisions), basically solves
the dynamic physics of the collision using inputs from
the impact and rest locations along with the weights of
the vehicles and other information such as the surfaces
over which the vehicles traveled from impact to rest.
GILLENgineering obtains the
inputs for these analyses from direct inspection of the site
of the accident and measurements of the damaged vehicles.
During the inspections, documentation via field notes,
photographs and/or videotape is made. If the accident site
has changed and the necessary physical evidence required to
locate the impact and rest locations no longer exists, but
photographs taken near the time of the accident are
available, photogrammetry is used to accurately reconstruct
the required dimensional information. Photogrammetry is also
used to measure the amount of crush on an accident vehicle
when only images of the vehicle exist, as is often the case
when vehicles have been totaled and destroyed.
Numerous other tests and analysis are performed by
GILLENgineering to determine HOW and WHY a specific accident
happened. The following list highlights some of the more
frequently encountered situations.
- Skidmark Analysis
- Headlamp Filament Analysis for On/Off Condition
- Skid Testing of the Road Surface at a Specific
Accident Site
- Visibility Studies for Obstructed Views at
Intersections
- Day and Night Visibility Studies
- Lighting Condition Visibility Studies
- Line of Sight Studies for Horizontal and Vertical
Curves
- Driver Reaction Time Analysis
- Driver Behavior Studies
- Occupant Restraint Examinations
- Pavement Marking Analysis
- Noise Level Analysis
- Pole Impact Analysis
- Low-Speed Impact Analysis
- Vehicle Rollover Analysis
- Roadway and Traffic Signage Analysis
- Trailer Disengagement
- Unintended Acceleration
- Weather Effects
- Tire and Wheel Failure Analysis
- Who Crossed the Centerline Analysis
- Who Was Driving Analysis
Complementary areas of Accident Reconstruction and
Transportation Engineering are described below.
- Transportation, Traffic
and Highway Engineering: An
Overview
-
Vehicle accidents occur within
the larger setting of Transportation, Traffic and Highway
Engineering. Said another way, it is the overall system of
Transportation, Traffic and Highway Engineering from which
traffic accidents come forth.
It is often the case that
traffic accidents occur as the result of more than one
factor. This is true of most failures occurring in the human
made world. We are very good at accounting for any single
cause of a catastrophe, and avoiding it or minimizing the
harmful effects of it. The problem is nature frequently has
multiple causes occurring near the same point in time. Some
causation events have a bigger impact on the outcome of an
accident and others have a lesser impact.
- Evaluating accidents in the
Transportation, Traffic and Highway Engineering system is
really a matter of assessing the known causative elements
of the accident event. Accident Reconstruction and
Transportation, Traffic and Highway Engineering overlap
in the determination of the causative elements.
An accident within
our human engineered systems frequently occurs at the
confluence of several causes.
Railroad and Railroad Grade
Crossing Accident Reconstruction: In
Scale
We all know trains are
obviously bigger than cars. What is the scale? What physical
units should we choose to measured the scale? For analyzing
the potential for damage and injury, it is most helpful to
look at momentum and energy. The ratio of the momentum of a
2500 pound car traveling 30 mph to a 100,000 pound locomotive
traveling 65 mph is 1 to 86. The ratio of the energies for
the same two vehicles is 1 to 185. Said another way, a
locomotive going 65 mph has 185 times as much energy as a
midsize car going 30 mph. These ratios are calculated for a
single locomotive engine. Image the ratios if we considered
an entire train loaded with coal.
These ratios illustrate why it
is so perilous to be in the path of a train. But these
situations continue to occur throughout the world. In October
of 1995, at a grade crossing in Fox River Grove, Illinois,
seven high school children were killed and twenty-four
passengers were injured when a commuter train struck a bus.
These horrendous loses focused the attention of the nation.
In addition to the investigation by the NTSB and others to
determine the cause of this accident, a nationwide search was
immediately begun to locate other grade crossings where
preemption conflicts could possibly exist.
Following the Fox River Grove
accident the U. S. Secretary of Transportation mobilized a
task force to review the decision-making process for
designing, constructing and operating rail crossings. An
associated 24-person working group has reviewed the findings
of the task force and helped develop a series of
recommendations and an action plan. Their report,
"Accidents That Shouldn't Happen" was released in
March of 1996. The principle finding was that better
cooperation, communication and education are necessary among
responsible parties if accidents and fatalities are to be
reduced at highway-rail grade crossings.
Partially because of the
physical ratios given above, at-grade highway-rail grade
crossings demand a higher level of safety than is warranted
in many other driving situations.
- Motorcycle Accident
Reconstruction: At Risk
It's exhilarating. It's
freedom. It's just you, the road and the machine. I know. I
ride. Therefore, I am. Motorcycles are extremely easy to
control and perform via a well-defined set of dynamics that
are intuitive to the rider. Their ride is mobile and fluid,
requires some level of rider interaction and brings the rider
close to the elements: the feel of the cool air when dropping
down into a small valley or depression at dusk, the smell of
fresh cut clover when passing a field, the feel of increased
gravity when leaning into a sweeping curve.
But, it is risky
transportation, whether for fun, commuting or other
activities. A motorcycle rider has the exposure of a
pedestrian (there is no occupant compartment to protect the
rider) and the velocity of a motor vehicle. Drivers of other
vehicles don't always anticipate or look for motorcycles. At
the event of some disturbance, either at the road surface or
in the environment, two wheels are not as stable as four
wheels.
Risks of injury can be
minimized by wearing protective clothing, especially a
quality, approved, full-face helmet. Risks of accident
involvement can be minimized by attending novice and
experienced rider training courses offered frequently in many
states. As for all driving, it is safer to travel in good
weather, on dry roads, at modest speeds and when we are
refreshed and have a clear mind focused on driving.
Reconstructing a motorcycle
accident is usually challenging, requiring special skills and
knowledge on the part of the engineer or reconstructionist.
These are obtained through experience, study and training.
Broad personal experience as a rider is a necessity for
accurately analyzing motorcycle related accidents.
- Field Investigation and
Documentation: Its Basic
-
Field inspections of accident sites and vehicles are one
of the best sources of physical information. To experience
the site where an accident happened is vastly more
informative than viewing photographs of the same location.
Although scene photographs taken when the physical evidence
still exists and shows in the photographs are additionally
helpful. Such scene photographs can be used to quantify
locations, skid marks, debris, vehicle crush and conditions
through the use of photogrammetry.
Thus they compliment the accident site investigation.
A note on semantics: There is often confusion between the
terms accident scene and accident site. The
distinction is, the scene is available only
immediately following the accident, when the people and/or
vehicles are still there. But once the normal everyday
activities return to the location, it is henceforth called
the accident site.
The most important tool to take to an inspection is an
open mind filled with keen, experienced powers of
observation. As defined above, accidents often have many
contributing causal circumstances. A casual inspection
gleaning only the obvious often overlooks important
considerations.
But once the observations have been made mentally, it is
crucial to document the findings so they can be shown or
demonstrated to others. The following is a partial list of
tools helpful in this process and routinely employed by
GILLENgineering.
- 35 mm SLR Camera with lenses, filters, tripod,
etc. and calibrated for photogrammetry
- Nikon CoolPix 700 Digital Camera
- Hi-8 Video Camera with accessories
- Total Station for Surveying
the Accident Site or Vehicle(s)
- Vericom VC200 Accelerometer for Skid Testing
- Drag Sled for Skid Testing
- 25', 100' and 200' Measuring Tapes
- Rolatape Measuring Wheel, 12" diameter
- Hand Level
- Compass
- Inclinometer
- Plumb bob
- Dentist mirror
- 6" ruler with fine graduations
- Caliper
- Impression Compound for collection of surface
shapes for microscopic analysis
- VOX microcassette Voice Recorder
- Various Chalk and Markers
- Specimen bags
- Flashlight
- Air Pressure Gauge
- Tread Depth Gauge
Last modified: February 08, 2005
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