Friday, November 23, 2012

Vehicle Impact speeds are usually needed for a biomechanist to determine occupant motion and forces experienced during the crash

Vehicle Impact speeds are usually needed for a biomechanist to determine occupant motion and forces experienced during the crash

Traffic accident reconstructionists are primarily used to determine the impact speeds and the delta-V for the vehicles involved in the crash. In the majority of crashes, the accident reconstructionists will use information from skid marks, road surface friction, pre-impact and post-impact directions for each vehicle, point of impact, distances that each vehicle moved after the collision, crush width and depth, and other factors to determine the impact velocities and delta-V’s. This information may be noted in the police report, medical records, repair estimates, photographs, or in recorded statements or depositions of parties involved in the crash. In essence, kinetic energy and/or momentum are used by these experts to establish their database as well as using crash tests to compare with the actual collision. The type of crash and facts in the case establish the approach that the reconstructionist will use. These speeds are then used by the biomechanics experts for their determination of injury mechanisms, forces, and injury risks.
               Since 1977 all new production vehicles have event data recorders (EDRs) or “Black Boxes” that collect impact data and make decisions about whether to deploy or to not deploy the frontal airbag in a crash. However, only a limited number of manufacturers have provided private industry, including police departments, with a decoder device and software to access the data on the module. For and General Motors have led the industry by providing the private industry with the ability to download the data from the EDRs. At present, these “Black Boxes,” are limited to recording the delta-V of the vehicle, seatbelt use/nonuse, airbag enabled/disabled, time of impact relative to airbag deployment , the status of the brakes (on or off), and the percent of throttle use/engine RPM and vehicle speed before the algorithm is activated. There are many varieties of EDRs available and there is no standardized format among the different manufacturers for storing and retrieving the electronic data. EDRs have differing data parameters between models and manufacturers, and this some measure average acceleration values whereas others only show peak acceleration values. Differing levels of delta-Vs or acceleration thresholds for activation as well as recording time can be set. These systems have to be customized for the size of the vehicle. Airbag deployment protocols will differ in small cars compared to a large SUV. If the data from an EDR is properly evaluated, it can provide an impartial source of evidence for the reconstruction and biomechanics community. EDR data has been successfully used as evidence in trails. Most consumers are not aware of these recorders in their vehicles, and it may come as a surprise for all parties that one exists. If anyone is aware that an EDR is present in a case, it is critical to get signed authorization by the owner of the vehicle, or owner’s counsel, before retrieving electronic data from EDR or removing the recorder, and to make certain to document the “chain of evidence,” that is, who removed and has the device, making certain there has been no tampering or misuse of the EDR. EDRs continue to evolve and the data from the device are considered to be accurate and therefore reliable for its intended purposes. According to a recent NHTSA working group, the owner of the vehicle owns the data from the EDR. More information on EDR benefits versus limitations can be found on the Internet. The manner in which the EDR was removed, how the device has been stored, and how the downloaded data (evidence) has been protected is critical for criminal cases.
               The plaintiff and his or her treating health care providers and expert witnesses have the “burden of proof” in civil cases relating to traffic accidents. In contrast, the insurance industry is not in the business of collecting unnecessary evidence or getting information that can potentially be used against them. This means that if the case goes into litigation, the plaintiff needs to be able to prove his/her injuries. There needs to be enough information in the police report, repair estimate, and photographic evidence for the plaintiff’s reconstructionists to calculate crash speeds so the biomechanist can describe occupant motion and biomechanical aspects of the event. The reader may ask, why do I need to get involved, what should be advised, and if so, how can it be done in a short amount of time? Well, the doctor can greatly aid the case if the patient is advised to take photographs of his/her vehicle as soon as possible. In addition, advising the patient to photograph the vehicle before, during, and after repair is done can useful to the plaintiff’s reconstructionist. Positioning a tape measure next to the damage as each photo is taken clearly indicates where the damage is located and the depth of the crush. These measurements can greatly increase the accuracy of calculating the crash speeds. In most cases where the plaintiff’s vehicle is totaled, the vehicle will be towed to a storage facility and then rapidly sold and removed by companies that scrap the vehicle. After investigating several hundred crashes, I have found a consistent trend for the claims adjusters to take photographs of marginal-to-poor quality and at mostly oblique angles, contrary to published accident reconstruction standards. Several recognized traffic accident reconstruction books have been available to insurance carriers for decades that can be used for training their claims persons. Most certainly these insurance carriers frequently hire defense reconstructionists who have been properly trained in the photographic standards and what is required to make accurate speed calculations from crush analysis. These reconstruction texts have clearly set the standards for taking photographs of vehicles involved in collisions. Either the majority of claims adjusters are trained to take lousy photos or they are not motivated to take views useful for reconstructionists. In vehicles that are towed away and totaled, the speedy sale to contracted companies does not allow time for photographs to be taken in most cases. If the crashed vehicle is in a storage facility, often the owner is either not allowed or strongly urged to not take photos by the persons managing the facility. To provide information for the case, the owner should insist on a photo session of his or her own vehicle. If an attorney is involved at the onset, the defendant’s insurance carrier can be notified that photographs must be taken of the vehicle before any repairs are made or the vehicle is sold.

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