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Tire-roadway frictional drag, an important consideration for transportation accident reconstruction, is dependant on vehicle, roadway and environmental factors. Vehicle factors include vehicle specific properties such as geometry and inertial parameters, braking system type, tire size, and tire properties. Roadway factors include grade, pavement type, construction, pavement age, and other parameters. Environmental factors include temperature and inclement weather. In order to control these (and other) vehicle, roadway, and environmental factors, the determination of tire-roadway frictional drag is done through staged testing using an instrumented vehicle. Staged testing is typically performed with an exemplar vehicle on a similar roadway under comparable environmental conditions. Engineering instrumentation includes acceleration and velocity sensors as well as a brake gun to directly measure total braking distance.

For many years, crash testing performed for the US Department of Transportation National Highway Traffic Safety Administration (NHTSA) has been used to analyze and study trends in the measured Anthropomorphic Test Device (ATD) test responses in 48 kph (FMVSS 208) and 56 kph (NCAP) frontal barrier crash tests. Although many variables must be controlled in these tests, the initial seated position of the dummy has been found to significantly affect the measured dummy parameters (head acceleration, chest acceleration, femur loads). Data generated from the NHTSA sponsored testing is archived in the NHTSA Vehicle Crash Test Database (VCTDB). The present study is performed to analyze the driver ATD positions in frontal crash tests. First, a publication review was performed from which selected related seating position literature is discussed. The resulting relationships to design guidelines (e.g. SAE J standards) are also discussed.

Impact induced vehicle residual deformation serves as a basis for the reconstruction engineer to make a determination of the energy absorbed during the impact phase of a collision. Many impact phase reconstruction algorithms assume a linear relation between an absorbed energy function and residual crush in order to derive collision severity (Delta V, BEV, etc.). This is done through the assumption of a constant spring stiffness value to describe the vehicle frontal impact stiffness. However, some recent rigid barrier impact test data has demonstrated non-linear trends between crash energy and residual crush. The total body of available crash test data indicates that vehicle frontal stiffness cannot be precisely modeled through the use of a single linear spring stiffness for all vehicles. This paper will explore stiffness trends and make comparisons to the previously assigned linear assumption for a diverse sample of vehicles and test speeds into frontal fixed barriers.

The reconstruction of motor vehicle collisions requires an analysis and quantification of the impact phase of the vehicular collision. In order to study the dynamics and velocity dependence of the impact phase, a series of four rigid barrier impact tests were designed and conducted. These tests were structured to bracket publicly available government compliance test data for a specific make and model vehicle and to define the vehicle frontal crash response over a broad range of impact speeds. These tests also provide a basis for the analysis and comparison of the results of a common damage energy reconstruction technique. A car to car, front to rear, impact test using the same make and model vehicles, was conducted to allow the comparison of crush incurred in two different collision environments at similar Delta V (AV) exposure levels.

The accuracy of an accident reconstruction depends on the quality and quantity of the data available from which to make an evaluation. With the majority of ground transportation accidents, by the time a reconstruction is sought the only available data consists of the police report and photographs of the scene and involved vehicles. This paper addresses techniques developed for extracting the maximum information from the accident scene photographs. Principles of perspective drawing are explained and their relationship to photography is illustrated. Methodologies for perspective analysis of photographs to determine skid positions and lengths, vehicle positions of rest, etc. are explained with numerous actual photographic examples. A mathematical method of relating points on a photograph to a plan view drawing of the same scene is presented.

Eight full-scale collision experiments were conducted and 73 collision fire case studies were investigated to provide data relating to fuel system failure modes and susceptibility of fuel system designs to collision fires. Data regarding impact speeds, nature of injuries, and climatic conditions are included. Results of extensive laboratory experiments provide specific ignition conditions for common fuels and define ignition hazards of exhaust systems and electrical and lighting circuitry. The physics of crash fire atmospheres is described, including air quality, radiant and convective heat transfers, and the relationship between burn physiology and occupant escape time. Design concepts are suggested for limiting fuel spillages, ignition sources, and thermal stress to motorists.