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Southwestern Collision Analysis
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Expertise and Services

The principals in our firm have detailed knowledge, expertise, and experience in many aspects of motor vehicle collision investigation and reconstruction, safety-related motor vehicle defects, traffic safety research, training and specialized safety presentations, and offer a range of associated services.

Motor Vehicle Collision Investigation
and Reconstruction

Collision Scene Evaluation
Physical evidence at the collision scene, such as tire marks, gouges, debris, and fluid spills, can provide direct evidence of the collision events to the experienced investigator. By carefully documenting, measuring, and photographing the evidence at a crash site, scale diagrams of the collision scene can be developed. Detailed analysis of the physical evidence can determine specific items of interest such the pre- and post-impact trajectories of vehicles involved in the collision, the location of the point of impact, and the precise configuration of the involved vehicles at impact. Scene measurements are frequently integrated into the scientific and mathematical reconstruction process in order to estimate parameters such as vehicle speed.

Vehicle Damage Analysis

Side-impact configuration Examination of the external damage resulting to vehicles from a crash can provide the investigator with evidence of the nature of the collision forces, so providing insight into the crash configuration, post-impact motion, occupant kinematics, and the collision performance of a vehicle's structural elements and its safety systems. Detailed measurements and photographs assist in the damage analysis process and can act as inputs for collision reconstruction elements such as establishing vehicle orientations at impact, and the changes in velocity (delta-V) that occur as a result of the collision.

Analysis of vehicle dynamics and occupant kinematics

Initial vehicle momenta and the impact configuration determine the post-impact trajectories of collision-involved vehicles. In turn, detailed analysis of the final-resting positions of the vehicles, and of the physical evidence relating to to the point of impact and the paths of travel of the vehicles, can be used to reconstruct the collision configuration. The collision forces usually result in abrupt vehicle deceleration and motor vehicle occupants will respond by moving into contact with portions of the vehicle interior. Such collision-induced motion is both predictable, from a knowledge of the laws of physics and analysis of the vehicle dynamics, and is often demonstrable through the identification of specific physical evidence relating to occupant contact.

Identification of occupant contact points

Specific areas of damage to the vehicle interior can often be identified as resulting from contact by the occupants. For example, an unrestrained driver in a frontal crash would be expect to make knee contact with the lower dashboard, chest contact with the steering wheel, and head contact with windshield. In contrast, the chest and hips of a fully-restrained occupant will load the seat-belt assembly, while their head and chest may well be cushioned by an air bag. Our experienced collision investigators can use their extensive knowledge of vehicle dynamics and occupant kinematics to determine the likely location of occupant contacts and conduct a careful inspection of the vehicle interior to identify and fully document such occurrences.

Loading striations on a seat belt D-ring  Cosmetic transfer on air bag

Evaluation of seat belt, air bag, and child restraint system performance

In a collision, a vehicle is subject to rapid deceleration, and large forces are brought into play on restraint systems in order to prevent occupants making forceful impacts with portions of the vehicle interior. Nevertheless, the occupants must interact with the available seat belts and air bags, and evidence of the restraining forces may then be evident. Usually, this takes the form of striations on plastic components such as seat-belt tongues and D-rings, as well as transfers on portions of the seat-belt webbing. Similarly, cosmetic and/or tissue transfers may be present on the fabric of deployed air bags. Careful examination of the restraint systems to identify and document such loading marks can provide definitive evidence that a seat belt or child restraint was in use at the time of a collision. In some circumstances, the evidence may show that, although the restraint was being used, it was actually configured in an improper manner.

Injury evaluation and determination of injury mechanisms

The nature and severity of the crash, the use (or non-use) of occupant restraint systems, and the location and degree of contact with the vehicle interior are all determinants for both the nature and extent of any resulting occupant injuries. Physical evidence from the collision-involved vehicle of specific occupant contact points may be correlated to individual injuries in order to positively identify the mechanism of the injury. Biomechanics and human tolerance to injury then provide additional insights into the particular injuries that an occupant may have sustained as a result of a crash. The mitigating effect of motor vehicle safety systems and, in particular, the collision performance of the available occupant restraints, can then be evaluated.

Scientific reconstruction

Motor vehicles in collision are subject to the laws of physics, and the mathematical formulations of these laws. By capturing the physical evidence at the collision scene (e.g. skid marks), and quantifying the vehicle damage (e.g. crush measurements), the severity of the collision can often be determined in terms of parameters such as initial vehicle speed and/or the speed change (delta-V) resulting from the crash. Scientific methods can often be applied to pre-impact braking, pre- and post-impact vehicle dynamics (momentum), vehicle yaw, free-flight trajectories, and vehicle crush (energy dissipation). Some recent vehicles are equipped with event data recorders (EDR) that can potentially provide objective and quantitative data relating to a specific impact. Our knowledgeable and experienced personnel can integrate all of the methods that are applicable to a specific collision situation and thus provide reasonably-accurate reconstructions of real-world collision events.

EDR crash pulse

Crash data retrieval from event data recorders (EDR's)

Event Data Recorders (EDR's) typically form part of the command and control system for air bag deployment. While many such systems are proprietary to specific manufacturers, an available Crash Data Retrieval (CDR) tool allows collision investigators to download and interpret data stored in supported EDR's following a collision. A wide range of data elements can be obtained from such systems, the specific parameters being dependent on the particular device installed. In general, EDR's can provide a time history of the crash pulse (as delta-V vs. t and/or acceleration vs. t). Many units also store a time series of pre-impact data elements, such as vehicle speed, engine speed (RPM), throttle position, and the status of the brake light switch. Analysis of such data, in conjunction with a review of the physical evidence from the collision scene and the involved vehicles, can be exceptionally beneficial in reconstructing a crash. The firm has the required equipment, knowledge and expertise to download EDR's, and to analyze and interpret the data so obtained.

Investigation and analysis of safety-related motor vehicle defects

Defects in the design, manufacture, and installation of motor vehicle components and control systems can result in loss of operator control with the consequent potential for crashes that may result in death or injury. When such incidents occur without any prior warning to the vehicle operator they are classified as safety-related motor vehicle defects. Transport Canada maintains a public complaint system in order to monitor and document such incidents, and compiles a database of vehicle recalls by Canadian manufacturers and importers. The principals in this firm have extensive knowledge of the motor vehicle defect investigation and recall process, resulting from long experience in this field.

Safety Research, Training and Education

Fatalities involving tilt-bed trucks Road and motor vehicle safety research programmes
Members of our firm have been involved in a wide range of road and motor vehicle safety research projects over a period of many years. Publications associated with this activity have included the results of work on motor vehicle safety systems, event data recorders, collision investigation and reconstruction, seat belt and air bag systems, and injury biomechanics. See the full list of our publications.

Training in the in-depth investigation of motor vehicle collisions

Members of the firm have provided training in collision investigation and reconstruction, and on motor-vehicle related trauma, for a number of professional groups across North America. This includes courses for both undergraduate and graduate university students, advanced courses for police traffic analysts and reconstrutionists, and workshops for physicians, forensic scientists and members of the legal profession.

Traffic safety lectures/presentations to public and private groups

Invited presentations on various aspects of road and motor vehicle safety have been made to a wide variety of interested parties, including physicians and nurses, law enforcement personnel, and a number of public safety organizations.

For further details of any of the above aspects of our activities, or to make any other form of inquiry, please feel free to contact us at your convenience.

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