The reconstruction of an accident involves detailed and rigorous analysis of evidence, an understanding of the principles of physics, and the ability to apply related research, techniques, and processes. For decades, our experts have researched, tested, and published on related topics of airbag control modules, low speed collisions, tractor trailer impacts, high speed loss of control, and numerous other specialized topics to gain the level of knowledge needed to determine and evaluate how a crash occurred.
The following peer-reviewed, scientific publications demonstrate our expertise in general accident reconstruction.
This paper presents analyses of 21 real-world pedestrian versus vehicle collisions that were video recorded from vehicle dash mounted cameras or surveillance cameras. This research examined the specific interaction of non-frontal, side-impact, and minimal overlap pedestrian impact configurations to assess the relationship between the speed of the vehicle at impact, the motion of the pedestrian before and after impact, and the associated post impact travel distances. Named among the “Best Papers of SAE WCX 2021,” this paper was selected to appear in SAE International’s Journal of Advances and Current Practices in Mobility, 2021.
Pycrash is a free, open-source Python-based software package that can perform basic accident reconstruction calculations and other related functions. In this paper, Pycrash’s capabilities are examined and its accuracy is evaluated using matching PC-Crash simulations.
This paper introduces a method for calculating vehicle speed and uncertainty range in speed from video footage. The method considers uncertainty in two areas; the uncertainty in locating the vehicle’s position and the uncertainty in time interval between them.
Typically, most vehicles equipped with non-powered wheels use a spindle that not only supports the weight of the vehicle but also allows the rotation of the tire. The rotation of the hub and wheel on the spindle is accomplished with the use of either a tapered or double row ball bearing. This paper will discuss the failure of a spindle and wheel assembly that experienced fatigue due to improper pre-load of the spindle nut.
Eyewitnesses can provide valuable information regarding a specific incident to law enforcement, the legal industry, or technical investigators. However, it has been illustrated in various experiments and research that witness accounts and estimates (i.e. distances, times, and speeds) are often inherently unreliable, especially in emergency situations. The purpose of this study was to understand specific vehicle collisions with respect to impact speeds, vehicle damage, driver biomechanics, and eyewitness reliability of speed and distance.
Accidents involving heavy trucks turning left across travel lanes of a roadway are common subjects of investigation in the field of accident reconstruction. This paper will investigate the longitudinal and lateral accelerations of heavy trucks during small, medium, and large radius turns and analyze peak and average lateral accelerations as they relate to turn radius and vehicle speeds. This paper was selected to appear in SAE International’s Journal of Advances in Current Practices in Mobility, 2020.
This research evaluates a methodology for calibrating in-field sounds for playback in a different environment. The ability to record sounds in the field, and play them back accurately in a different environment, is useful when the end listener cannot be present at the location where the sound is being produced live. Each step of the methodology is detailed within this paper.
This paper evaluates event data from the Sensing and Diagnostic Module (SDM) of a sedan during high speed yaw testing involving tires that were intact and tires that had the tread removed. The authors examine the dynamic effect of high sideslip angles and changes to tire rolling radius, as a result of a tread separation, as it pertains to the accuracy of Event Data Recorder (EDR) reported vehicle speed.
In low speed collisions (under 15 mph) that involve a heavy truck impacting the rear of a passenger vehicle, it is likely that the front bumper of the heavy truck will override the rear bumper beam of the passenger vehicle, creating an override/underride impact configuration. The authors of this paper discuss three low speed impact tests that were conducted to expand the available data set for passenger vehicle dynamics and damage assessment for low speed override/underride rear impacts to passenger vehicles.
This paper presents a comprehensive analysis of the performance of Event Data Recorders (EDRs) found in the Airbag Control Modules (ACMs), as tested in support of the National Highway Traffic Safety Administration’s Frontal Oblique Offset Program. In addition to analyzing data from a high severity oblique frontal impact test in which the vehicle was struck by a moving deformable barrier, the authors also examine the results of EDR data downloaded from two 2015 model year Toyota Highlanders, and the results of EDR reported change in velocity (delta-v), to vehicle mounted accelerometers and reference instrumentation.
Several papers published over the past 25 years examine the acceleration of heavy trucks, providing a large data set that measures the speed, distance, and time of the vehicles during acceleration testing. The data is presented in tabular or graphical formats. There are approximately eight relevant papers with a total of 268 acceleration tests performed, spanning many years. This paper reviews all the available published literature and summarizes the relevant data in a comprehensive list of accelerations for different heavy truck configurations, providing a valuable resource to the accident reconstruction field.
Crash severity can be assessed by measuring crush damage (permanent deformation) and using crash test data. Reconstructionists typically use data from the NHTSA Vehicle Crash Test Database to calculate the A and B crush stiffness coefficients for a particular vehicle, but sometimes available data is insufficient. Therefore, it is useful to have generic trends to rely on. In this study, vehicles produced from 1973 to 2014 were classified by type, origin, and weight class, and correspondingly calculated the average A and B crush stiffness coefficients for each classification (as well as the standard deviation). We have also calculated the average A and B crush stiffness coefficients for several different year spans from 1973 to 2014, and have noted some trends.
More than 3,300 bicyclists were killed in crashes (presumably involving vehicles) between 2008 and 2012. 74% of all bicyclist deaths occurred as a result of crashes where the bicyclist (travelling in a straight manner) was struck by the front of a passenger vehicle. Bicycle speed is an important factor to consider in these investigations, however this is often difficult to assess. Given that the bicycle speed is often unknown, the alternative is to assume a reasonable range of bicycling speeds based on previous findings in relevant literature. The purpose of this article is to summarize bicycling speeds from several different papers, for ease of reference.
One type of collision scenario between a motor vehicle and a bicycle involves a cyclist travelling along the side of the road, and a vehicle attempting to overtake the slower-moving cyclist. Such scenarios account for 4.3% of bicycle collisions, and 28% of these collisions resulted in serious or fatal injuries. The purpose of this pilot study was to quantify the “normal” or “everyday” lateral acceleration rates that are used by cyclists in a simulated closed track performance test. Additionally, this study also examined acceleration and deceleration rates (both typical non-emergency and maximum effort) in cyclists varying in age and experience.
When reconstructing pedestrian impacts, it is important to identify the time to impact available. One of the assumptions when calculating the time to impact is the speed of the pedestrian. Although most pedestrian collisions (including fatalities) occur midblock, most of the research conducted for pedestrian speeds is based on pedestrians travelling in a controlled environment. In this study the midblock movement of pedestrians was compared to the gap between the pedestrian and the primary hazard vehicle. In addition, the relationship between the speed of the pedestrian and the lane in which the primary hazard vehicle was positioned was also analyzed.
Whether it is a photograph, surveillance video or in-cab video footage, physical evidence documented through these types of visual media can determine the quality and thoroughness of the crash reconstruction. This paper examines how it can also help shorten the length of time the reconstruction takes and ultimately reduce the costs without diminishing accuracy.
This paper will show the level of energy which a random sample of safety glasses can withstand. The author also compares the results to the current standards. Independent testing has shown that the performance of modern safety glasses exceeds the minimum requirements of the absorbed energy.
A primary goal of crash reconstruction (or collision avoidance system) is to determine whether a crash is avoidable or not. A prerequisite for the determination of avoidance is knowledge of the time that is available to a driver. In a path intrusion crash scenario, a method to determine the time available for a major road driver is to know the time a minor road driver accelerated before impact. This study is an attempt to model the time based upon acceleration distance.
Physical evidence deposited by vehicles as a result of an accident may not always be fully documented by the investigating law enforcement officers by means of measurements. The forensic engineer may require more detailed information regarding the physical evidence than is shown in the photographs or measured by the officers. This paper discusses three methods (Camera Matching, Photogrammetry, and Rectification) of collecting the physical evidence from several sources and the procedure of producing a comprehensive forensic map of the evidence relative to the roadway and the dynamic motion of the vehicle.
During the approach phase of an impact, the vehicle structure absorbs energy as it crushes to a maximum depth. This phase is followed by the restitution phase, during which the structure rebounds partially and restores some of the energy that it absorbed. This paper describes, demonstrates, and validates a method for incorporating the effects of restitution into crush analysis.
This paper addresses the inconsistency and confusion in the literature of accident reconstruction regarding when crush analysis and conservation of energy analysis should use the absorbed crush energy and when it should use the dissipated crush energy. This paper clarifies the relationship between the two and explores the use of each in both crush analysis and conservation of energy analysis.
On a cold winter morning in the Midwestern United States, an extraordinary sequence of events culminated in an explosion that destroyed the boiler of a coal- and gas-fired power plant, resulting in physical damages and lost revenues estimated to be in excess of $500 million. This paper points out how the explosion was the accumulated effect of many mistakes and could have been prevented by management, operations, or maintenance.
This paper examines the validity of the effective mass concept used in the CRASH 3 damage analysis equations. The results of this research show that the effective mass concept accurately models the effects of collision force offset when certain conditions are met. These conditions are discussed, along with their implication for damage interpretation.
Residual tensile stresses near the edges of windshields are currently produced in the manufacturing process. This stress reduces the ability of the windshield to withstand suddenly applied external loading over a short time interval near the edge. This paper presents the Knott Laboratory findings and conclusions about the application of a thin film of polycarbonate around the perimeter of the windshield.
This article examines airbag components and deployment systems; advanced airbag concepts, including cascade airbags, child seat sensors, side impact airbags, and side impact head protection; seat belt development; upper-extremity and facial injuries from steering wheel airbag deployments; and National Highway Traffic Safety Administration (NHTSA) response to airbag injuries.
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