Pedestrian & Cyclist Accident Reconstruction

Exponent’s scientists and engineers have deep experience analyzing and reconstructing pedestrian and cyclist collisions, and particular expertise addressing the unique challenges such collisions present. Our accident reconstructionists are highly skilled at analyzing the accident scene and damage and assessing forces that the vehicle or object imparts on the rider or pedestrian.

Using this information, Exponent’s biomechanical consultants gather and study information about injuries, interpret physical evidence, and apply engineering principles using the scientific method to analyze how an injured pedestrian or cyclist interacted with a vehicle, the ground and/or other environmental structures. Such analyses include determination of the pedestrian/cyclist kinematics of a particular incident, an assessment of forces applied to the human body, and a correlation of injury mechanisms with vehicle interactions.

Additionally, Exponent’s human factors scientists assess the effects of human factors, such as driver and/or pedestrian/cyclist distraction or inattention, sight lines, and pedestrian/cyclist visibility and conspicuity, on the occurrence and mitigation of a particular incident. Our ability to investigate, evaluate, and present the findings related to pedestrian and cyclist collisions are enhanced by advanced modeling and novel testing capabilities. We continue to work on the cutting edge of testing and research to better understand how product design can influence the outcome of pedestrian and cyclist collisions.

Collisions with motor vehicles can result in pedestrian and cyclist injuries. Cyclist injuries can also occur in collisions with stationary objects or in non-collision bicycle crashes. Factual evidence can be acquired through detailed review of the medical records with the assistance of a registered nurse; evaluation of radiological imaging with a board certified radiologist; inspection of the incident site and any involved vehicles; and a review of available documentation, including witness statements and legal testimony, police reports, and photographs.

Using the available evidence, including physical evidence and documented injuries, Exponent’s biomechanical consultants integrate the laws of physics, findings from published research, and, when required, testing at Exponent’s Phoenix Test and Engineering Center to determine how an involved pedestrian or cyclist likely interacted with involved vehicles and moved during a particular incident.

After the components of a pedestrian or cyclist’s interaction with a vehicle are known, they can be assembled in 3-dimensions to provide a clear illustration of the geometry and kinematics underlying the interaction. Application of biomechanical knowledge to the physical evidence allows our team to define and assess the specific mechanical loading environment resulting from a particular accident scenario and the resulting kinematics.

Pedestrian ad Cyclist Accident Reconstruction table 
Table 1. Pedestrian Interaction Reconstruction. In the pedestrian impact shown above, four interaction phases were identified and uniquely matched with the mechanism of the subject pedestrian’s injuries (bottom row). Using this reconstruction based on vehicle evidence and injury mechanisms, impact forces and pedestrian kinematics were assessed. These findings enabled determination of key conclusions regarding projection distance and approximate location of the point of impact.

Many other factors can influence the biomechanics of an incident involving a pedestrian or cyclist. In the case of a single cyclist, the rider’s helmet use can significantly affect the occurrence and severity of injuries. Exponent has extensive experience and unique capabilities related to evaluating helmet use and its role in injury mitigation. Exponent also has experience and testing capabilities for case-specific evaluation of pedestrian and cyclist protection, impact avoidance, and injury mitigation potentially provided by crash avoidance and pedestrian protection automotive technologies.

Assessment of road hazards and possible sight line obstructions can also affect the responsiveness of both drivers and pedestrians/cyclists. Additionally, attentional factors, such as distraction by cell phone use, inattention owing to fatigue, alcohol consumption, or medication use, can further impact a driver’s or pedestrian’s/cyclist’s ability to respond in a timely fashion to an impending collision. Moreover, the limited visibility of pedestrians/cyclists at low light conditions, the conspicuity of a pedestrian/cyclist, and driver or pedestrian/cyclist expectation can influence whether a collision is avoidable or not. Finally, pedestrian/cyclist or driver risk perception and risk taking can play a decisive role in pedestrian and cyclist accidents. Exponent’s Human Factors scientists have the ability and experience to perform comprehensive analyses of these elements and their effect on incident outcomes.

In addition to conducting case specific analyses, Exponent has extensive novel experiment design and implementation capabilities. Our Phoenix testing facility is equipped to conduct human motion tracking experiments; head impact and helmet use experiments; handling and maneuverability evaluations; vehicle and pedestrian ATD testing; and full scale crash tests among many others. Exponent’s experts continually conduct research and implement experiments to remain on the cutting edge of understanding how pedestrian and cyclist collisions occur as well as how protection systems may mitigate these hazards.


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