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Crash Forensics provides complete motor-vehicle forensic crash reconstruction services, including the following:
- Documentation and analysis of physical roadway evidence, including Forensic Mapping.
- Documentation and analysis of physical vehicle damage evidence including Forensic Mapping of
vehicle damage profiles.
- Downloading of automobile and truck event data recorders.
- ยท Mathematical reconstruction of vehicle speed and positions before, at, and after impact.
- Preparation of expert reports.
- Depositions and trial testimony.
Below is a detailed explanation of crash reconstruction to allow you to better understand what it is. Link to our reconstruction experts.
Crash reconstruction, as a process commonly applied to motor-vehicle collisions, determines pre-impact circumstances from physical evidence at the crash scene. It is most dependent on the physical equations developed by Sir Isaac Newton, most commonly referred to as Newtonian Physics. For purposes of analysis here, the mathematical relationship between energy dissipation and work, the principle of Conservation of Energy, and the principle of Conservation of Linear Momentum will all be applied. Crash reconstruction, however is also as much art as it is science. The art is knowing which equations apply to each crash, knowing what input assumptions are reasonable, knowing what factors constrain a solution (such as one vehicle cannot physically pass through another), and knowing when independent methods can be applied to validate a solution.
A crash investigation can consist of many aspects. However, the investigation usually starts with an inspection of the crash site, where measurements are taken of evidence left by the vehicles such as point of impact, final resting positions, skid marks, scrub marks, and gouge marks. These measurements are usually taken using electronic surveying equipment. With this equipment, a computer-generated scale diagram can be produced and may be used to reconstruct the crash.
With the crash investigation complete, a crash reconstruction can be performed. Reconstruction is the process of using physics to determine the speeds of the vehicles, and/or their relative positions at different times during the crash sequence. Information such as the pre- and post-impact direction of travel, the length of pre-impact skid marks, the post-impact distances moved, the friction values for the various surfaces the vehicles traveled over, the point of impact, the impact angles, and the weights of the vehicles are all inputs to the equations used in reconstructing an crash.
A slightly more complex crash reconstruction involves two vehicles first skidding, then colliding with each other, then sliding to a stop. For this type of crash the method used is called the Conservation of Linear Momentum, which takes into account the weights of the vehicles, the point of impact, the angles at which they collided, and the places where they came to rest. To be more specific, take the example of two-vehicle collision where one vehicle is traveling due south the other vehicle is traveling due west. After these two vehicles collide, the rules of physics tell us they will move generally southwest, with all of the southward momentum resulting from the southbound vehicle and all of the westward momentum resulting from the westbound vehicle. If the reconstructionist knows how much each vehicle weighs, how far each vehicle moved south, how far each vehicle moved west, and what coefficients of friction were encountered, then he can calculate a collision speed for each of the vehicles. This collision speed for each vehicle can then be combined with its speed loss from pre-collision skidding to calculate its pre-braking speed.
In many cases, the reconstructionist is faced with the situation where he does not have complete information. This could be due to a poor evidence record or the result of other factors that cannot be accounted for. With incomplete evidence, the reconstructionist may make educated assumptions to account for the missing evidence. This is acceptable practice so long as the reconstructionist makes assumptions that are conservative to his client's position. Since assumptions can exhibit a bias in calculations, the expert's method should be designed so that the bias does not favor his client but instead will favor the client's opponent. This is what being conservative means. For example, if an assumption is made by a reconstructionist, for that assumption to be conservative it must produce higher speeds from his client's vehicle and/or lower speeds for the other vehicle.
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