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Rear impacts in the crash test data base compiled by the NHTSA are analyzed and compared to the CRASH3 rear stiffness coefficients. The CRASH3 values do not represent the test data adequately. This is because the values were derived from limited data, and because some of the rear moving barrier test data were miscoded as fixed barrier tests. A review of the larger NHTSA data base does not support the CRASH3 assumption that vehicles of similar size (wheelbase) have similar rear stiffness characteristics. Therefore, it is important when reconstructing individual accidents to use crash test data specific to the vehicles involved. Repeated rear fixed barrier test data on four vehicles are analyzed to study the data trend at speeds below and above the NHTSA test data. Constant stiffness and constant force models are compared and a combination of the two is shown to fit available test data.

The appropriateness of the set of eight frontal stiffness coefficients used by the CRASH3 program to estimate vehicle deformation energy (and to subsequently derive estimates of vehicle delta-V) is examined. This examination consists of constructing so-called CRASH energy plots based on 402 frontal fixed barrier impact tests contained in the NHTSA's Vehicle Test Center Data Base (VTCDB) digital tape file. It is concluded that the use of category coefficients within the CRASH3 program can result in large delta-V errors, reaffirming the inappropriateness of this program for use in individual accident reconstructions. The use of the CRASH3 category stiffness coefficients is seen to generally overestimate vehicle energy absorption for vehicles with small amounts of frontal crush and to underestimate vehicle energy absorption for vehicles sustaining large crush.

This paper summarizes work relating to the assessment of societal benefits of side impact protection. National Crash Severity Study (NCSS) and National Accident Sampling System (NASS) accident data technigues were reviewed with respect to the reliability of output information concerning the distribution of side impact accidents by impact severity and relationships between injury and impact severity. NCSS and NASS are confounded by errors and inadequacies, primarily as a result of improper accident reconstruction based upon the CRASH computer program. Based on review of several sample cases, it is believed that the NCSS/NASS files underestimate Lower severities and overestimate higher severities in side impact, with delta-V errors probably overestimated by 25-30 percent in the case of the more serious accidents. These errors cannot be properly quantified except on a case-by-case basis. They introduce unknown biases into NCSS/NASS.

A follow-up study on rollover testing was conducted along a section of a remote rural highway using six full-size sport utility vehicles (SUVs) of differing makes and models. The vehicles were instrumented and towed to highway speeds before being released, at which point an automated steering controller steered the vehicles through a series of maneuvers intended to result in rollover. A total of eight tests were conducted and documented, six rollovers and two non-rollover events. The six rollover events provide trip and tumbling conditions for each vehicle. The two non-rollover attempts produced cornering tire marks and allowed for the documentation of near roll conditions for the two out-of-control vehicles. All eight tests presented are instrumented real-world type tests that were later correlated based upon the data obtained.

Frontal, side, rear, pole and offset car to car data sets are examined using familiar damage analysis models: constant stiffness, bilinear stiffness, and force saturation. In addition to these, a non-linear power-law formulation is introduced and compared to the others. The power-law provides a nonlinear stiffness coefficient that transitions between a constant force model and constant stiffness model as the power goes from 0 to 1. It also provides a continuous, single valued function that is easily integrated and used in the analysis. Power-law nonlinearity can be used to smoothly fit low through high crush data. Geometric integral parameters are developed which represent irregular crush profiles. These permit graphical comparison of tests with non-uniform crush data (such as offset, side, and narrow object) with uniform crush test data. They also provide a means for comparison of accident damage with the test data set.

The data from a set of 45 reference cases, involving the collision of two generic automobile models, is presented as a basis for comparing collision algorithms used in motor vehicle accident investigation. The set was generated by the SMAC algorithm.

Performance and operational characteristics of several prototype containers for storing hydrogen are described. A cryogenic vessel and three metal hydride containers of similar design but different size have been used in automotive service. Hydrogen release rates were controlled to match with engine demand. All prototypes were able to sustain a steady state flow rate sufficient for vehicle operation at normal cruise speed. In order to illustrate the principle of hydride operation, a pressure--temperature history for recharge of a small portable hydride tank is given along with several discharge curves with and without heating.

A vehicle trajectory simulation called VTS has been developed as an aid for reconstruction of automobile accidents. The two dimensional vehicle has longitudinal, lateral and yaw degrees of freedom, a point mass at the center of gravity) yaw inertia about the center of gravity and four contact points (“tires”) which can be arbitrarily positioned. No collision or aerodynamic forces are modeled. The traction surface is represented as a flat plane with a specified nominal friction coefficient. Several quadrilateral “patches” may be applied to the surface to change the friction coefficient in specific regions. User vehicle control consists of timewise tables for steering angle and traction coefficient for each of the four wheels. When used individually or in conjunction with other computer modules, VTS provides a convenient, accurate modular tool for trajectory simulation.

The “IMPAC” collision algorithm is a comparatively simple application of momentum conservation in a collision. This 2-D model may be used in a number of applications: to reconstruct car to car collisions, to study car to barrier collisions, to evaluate proposed crash test conditions, to refine and check reconstruction calculations made using the “damage” option of “Crash3”, or as a predictor for the “SMAC” program to reduce the number of runs required to obtain a reconstruction. The program also provides a means of rapidly evaluating questions of sensitivity of results to changes in input. The essential features of the model are reviewed herein and two collision configurations are examined. The most recent version of the program provides output for purposes of comparison with the method employed by the “Damage” option of the “Crash3” program.

Three full-size sedans were towed to highway speeds along a section of a remote rural highway. Upon release, an automated steering controller steered the vehicles through a series of maneuvers intended to result in rollover. Repeated attempts to roll each vehicle were made until rollover resulted. Non-rollover attempts produced cornering tire marks by the out-of-control vehicle. Out of numerous runs, 3 rollover and 2 non-rollover tests were selected for documentation and analysis. One additional steer-induced rollover test is presented that was conducted along a simulated road section at a closed test-track facility. All six tests presented are instrumented real-world type tests that were later reconstructed based upon the data obtained from on-board instrumentation, videotape, survey measurements, and still photographs obtained of each respective test.

Crash behavior in narrow object impacts was examined for the perimeter of a 4-door full size sedan. Additional test data was obtained for this vehicle by impacting four sedans with a rigid pole mounted to a massive moving barrier (MMB) in the front, right front oblique, right side, and rear. The vehicles were stationary when impacted by the MMB. Two of the four cars were repeatedly impacted with increasing closing speeds in the front and side, respectively. Each test was documented and the resulting deformation accurately measured. The stiffness characteristics were calculated for the perimeter of car and were presented using the power law damage analysis model. The vehicle's crash performance in these pole tests was compared to that of NHTSA's flat fixed barrier tests (deformable and non-deformable) for the front, side, and rear of this vehicle.

Vehicle accident reconstruction methods based on deformation energy are argued to be an increasingly valuable tool to the accident reconstructionist, provided reliable data, reasonable analysis techniques, and sound engineering judgement accompany their use. The evolution of the CRASH model of vehicle structural response and its corresponding stiffness coefficients are reviewed. It is concluded that the deformation energy for an accident vehicle can be estimated using the CRASH model provided that test data specific to the accident vehicle is utilized. Published stiffness coefficients for vehicle size categories are generally not appropriate. For the purpose of estimating vehicle deformation energy, a straight-forward methodology is presented which consists of applying the results of staged crash tests. The process of translating crush profiles to estimates of vehicle deformation energies and velocities is also discussed.