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The objective of this study is to analytically model the fatality risk in frontal vehicle-to-vehicle crashes of the current vehicle fleet, and its sensitivity to vehicle mass change. A model is built upon an empirical risk ratio-mass ratio relationship from field data and a theoretical mass ratio-velocity change ratio relationship dictated by conservation of momentum. The fatality risk of each vehicle is averaged over the closing velocity distribution to arrive at the mean fatality risks. The risks of the two vehicles are summed and averaged over all possible crash partners to find the societal mean fatality risk associated with a subject vehicle of a given mass from a fleet specified by a mass distribution function. Based on risk exponent and mass distribution from a recent fleet, the subject vehicle mean fatality risk is shown to increase, while at the same time that for the partner vehicles decreases, as the mass of the subject vehicle decreases.

Forward Collision Warning (FCW) is a system intended to warn the driver in order to reduce the number of rear end collisions or reduce the severity of collisions. However, it has the potential to generate driver annoyances and unintended consequences due to high ineffectual (false or unnecessary) alarms with a corresponding reduction in the total system effectiveness. The ineffectual alarm rate is known to be closely associated with the “time to issue warning.” This results in a conflicting set of requirements. The earlier the time the warning is issued, the greater probability of reducing the severity of the impact or eliminating it. However, with an earlier warning time there is a greater chance of ineffectual warning, which could result in significant annoyance, frequent complaints and the driver's disengagement of the FCW. Disengaging the FCW eliminates its potential benefits.

Reliable testing of a mechanical system requires the procedures used for the evaluation to be repeatable and reproducible. However, it is never possible to exactly repeat or reproduce the tests that are used for evaluation. To overcome this limitation, a statistical evaluation procedure can generally be used. However, most of the statistical procedures use scalar values as input without the ability to handle vectors or time-histories. To overcome these limitations, two numerical/statistical methods for determining if the impact time-history response of a mechanical system is repeatable or reproducible are evaluated and elaborated upon. Such a system could be a vehicle, a biological human surrogate, an Anthropometric Test Device (ATD or dummy), etc. The responses could be sets of time-histories of accelerations, forces, moments, etc., of a component or of the system. The example system evaluated is the BioRID II rear impact dummy.

This paper reports a study undertaken by the Crash Safety Working Group (CSWG) of the United States Council for Automotive Research (USCAR) to determine generic acceleration pulses for testing and evaluating advanced batteries subjected to inertial loading for application in electric passenger vehicles. These pulses were based on characterizing vehicle acceleration time histories from standard laboratory vehicle crash tests. Crash tested passenger vehicles in the United States vehicle fleet of the model years 2005-2009 were used in this study. Crash test data, in terms of acceleration time histories, were collected from various crash modes conducted by the National Highway Traffic Safety Administration (NHTSA) during their New Car Assessment Program (NCAP) and Federal Motor Vehicle Safety Standards (FMVSS) evaluations, and the Insurance Institute for Highway Safety (IIHS).

The statistical analysis of vehicle crash accident data is generally problematic. Data from commonly used sources is almost never without error and complete. Consequently, many analyses are contaminated with modeling and system identification errors. In some cases the effect of influential factors such as crash severity (the most significant component being speed) driver behavior prior to the crash, etc. on vehicle and occupant outcome is not adequately addressed. The speed that the vehicle is traveling at the initiation of a crash is a significant contributor to occupant risk. Not incorporating it may make an accident analysis irrelevant; however, despite its importance this information is not included in many of the commonly used crash data bases, such as the Fatality Analysis Reporting System (FARS). Missing speed information can result in potential errors propagating throughout the analysis, unless a method is developed to account for the missing information.

A data processing algorithm is presented for determining the spatial orientation and position of a rigid body in impact tests based on an instrumentation scheme consisting of a triaxial angular rate sensor and a trialaxial linear accelerometer. The algorithm adopts the unit quaternion as the main parameterized representation of the spatial orientation, and calculates its time history by solving an ordinary differential equation with the angular rate sensor reading as the input. Two supplemental representations, the Euler angles and the direction cosine matrix, are also used in this work, which provide an intuitive description of the orientation, and convenience in transforming the linear accelerometer output in the instrumentation frame to the global frame. The algorithm has been implemented as a computer program, and a set of example impact tests are included to demonstrate its application.

Developing an effective side impact ATD for assessing vehicle impact responses requires a method for evaluating that ATD's bio-fidelity. ISO/TR9790 has been in existence for some years to serve that purpose. Recently, NHTSA sponsored a research project on the post-mortem human subjects (PMHS) responses subjected to side impact conditions. Based on those newly available PMHS data, Maltese generated a new approach for creating bio-fidelity corridors for human surrogates. The approach incorporates the time factor into the evaluation equation and automates the process (Maltese et al. 2002). This paper serves as the first attempt to look closely at the new bio-fidelity corridor generation process (hereafter referred as the Maltese approach) with respect to its validity, effectiveness, as well as its practicality. The effect of mass scaling was first examined in order to ensure the integrity of the data. The time alignment scheme and the formation of the corridors were then tested.

The effects of vehicle “stiffness” and mass on the occupant response during a crash may be determined by evaluation of accident data. However, “stiffness” and mass may be correlated, making it difficult to separate their effects. In addition, a single-valued “stiffness”, although well defined for linear case, is not well defined for non-linear systems, such as in vehicle crash, making the separation task even more difficult. One approach to addressing the lack of a clear definition of stiffness is to use multiple definitions. Each stiffness definition can then be correlated with mass to look for trends. In this study, such an approach was taken, and the different stiffness definitions were given and their values were obtained from rigid barrier crash test data. No clear relationship between mass and stiffness appears to exist. All the stiffness measures reviewed show, at best, only a weak correlation with mass. A stiffness analysis among different vehicle types was also carried out.

This paper presents an energy relationship between vehicle impact pulses and restraint systems and applies the relationship to formulations of response factors for linear and nonlinear restraints. It also applies the relationship to derive optimal impact pulses that minimize occupant response for linear and nonlinear restraints. The relationship offers a new viewpoint to impact pulse optimization and simplifies the process mathematically. In addition, the effects of different vehicle impact pulses on the occupant responses with nonlinear restraints are studied. Finally, concepts of equivalent pulses and equal intensity pulses are presented for nonlinear restraints.

A simple spring-mass model of the impact response of the side impact dummy (SID) is established. The spring and mass constants of the model are established through system identification methodology based on data from impact tests. The tests are performed in laboratory with hydraulically driven impactors impacting the chest and pelvis of the SID. The input data to the model consist of measured contact force or impactor velocity time histories, and the output data are accelerations on the rib, spine, and pelvis of the SID. The established model appears to predict the test results with reasonable accuracy. The main purpose of this study, however, is to use this simple model to carry out parametric studies of the response of the dummy with changing impact parameters, the result of which would be useful in understanding vehicle crash tests using the SID.

The response of the spine acceleration to rib and pelvis acceleration input of the side impact dummy (SID) is modeled using system identification methods. The basis for the modeling is a simplified representation of the SID by a 3-mass, 2-spring system. Based on this spring-mass representation, two types of response models are established. The first is a "gray-box" type with rib/pelvis-spine relationship modeled by Auto Regression with eXogeneous (or eXtra) input (ARX) type system models. The structure of these models is partially based on the spring-mass simplified representation, hence the notion "gray- box." The parameters of these models are identified through linear regression from test data. The second type of models is noted "physical model" here, since it is strictly a state- space form of the equation of motion of the simple spring-mass representation.

This paper outlines a method for estimating the probablistic nature of airbag crash sensor response and its effect on occupant position. Probability surfaces of airbag fire times are constructed for the impact velocities from 0 to 40 mph. These probability surfaces are obtained by using both frontal offset deformable barrier and frontal rigid barrier crash data. Another probability surface of displacement is constructed to estimate the occupant displacement time history before airbag deployment. This probability surface is constructed by using the initial occupant seating position data and the vehicle impact velocity and deceleration data. In addition, the probability of airbag firing at a given crash velocity is estimated from NASS-CDS, frontal offset and rigid barrier crash data.

The effects of stress in brain material was investigated with experimental and computational idealizations of the head. A water-filled cylinder impacted by a free traveling mass serves to give insight into what could happen to the brain during impact. Under an impact of sufficient velocity, cavitation can occur on the cylinder boundary opposite impact. Limited internal vaporization of the fluid may also occur during severe impact events. Cavitation occurred in these experiments at accelerations greater than 150 g's. Head forms of different sizing will experience an acceleration magnitude inversely proportional to the size difference to produce a similar pressure/cavitation response.

A comparison of the NHTSA advanced dummy and the Hybrid III is presented in this paper based on their performance in twenty four frontal impact sled tests. Various time histories pertaining to accelerations, angular velocities, deflections and forces have been compared between the two dummies in light of their design differences. This has lead to some understanding about the differences and similarities between the NHTSA advanced dummy and the Hybrid III. In general, the chest as well as the head motion in the NHTSA advanced dummy are greater. The lumbar moments in the NHTSA advanced dummy are lower than that in the Hybrid III. The upper and lower spine segments in the NHTSA advanced dummy, generally rotate more than the spine of the Hybrid III.

Supplemental airbag safety restraint systems are an integral part of today's vehicle package. This inflatable restraint technology relies heavily on woven fabrics and particularly on knowledge pertaining to a fabric's permeability as a function of pressure drop, inflation temperature of the gas and fabric weave. While fabric permeability can be quantified by actual experimental measurements, the number and non-linearity of the variables involved make the experiments time and cost intensive. Moreover, interpolations within a given data set yield questionable results. For these reasons a feed-forward artificial neural network (ANN) technique was utilized to predict fabric permeability. This is an interpretive procedure. An ANN routine must first be trained. During this training the ANN is introduced to actual cause and effect patterns with adjustments being made by changes in weighting factors until the errors in the output variables are minimized.

The response of the head to blunt impact was investigated using anesthetized live and repressurized- and unrepressurized-postmortem Rhesus. The stationary test subject was struck on the occipital by a 10 kg guided moving impactor. The impactor striking surface was fitted with padding to vary the contact force-time characteristics. A nine-accelerometer system, rigidly affixed to the skull, measured head motion. Transducers placed at specific points below the skull recorded epidural pressure. The repressurization of postmortem subjects included repressurization of both the vascular and cerebrospinal systems.

Mechanisms of thoraco-abdominal trauma were investigated utilizing unembalmed, repressurized human cadavers subjected to frontal impact with a steering wheel assembly. The focus of this research program was on trauma to the soft-tissue organs surrounded by the thoracic cage, as well as on the kinematic response of the thoracic cage. The results are compared to other thoraco-abdominal research programs conducted at the University of Michigan Transportation Research Institute (UMTRI) during the last eight years.

This paper discusses techniques developed and used by the Biosciences Group at the University of Michigan Transportation Research Institute (UMTRI) for measuring three-dimensional head motion, skull bone strain, epidural pressure, and internal brain motion of repressurized cadavers and Rhesus monkeys during head impact. In the experimental design, a stationary test subject is struck by a guided moving impactor of 10 kg (monkeys) and 25 or 65 kg (cadavers). The impactor striking surface is fitted with padding to vary the contact force-time characteristics. The experimental technique uses a nine-accelerometer system rigidly affixed to the skull to measure head motion, transducers placed at specific points below the skull to record epidural pressure, repressurization of both the vascular and cerebrospinal systems, and high-speed cineradiography (at 1000 frames per second) of radiopaque targets.

Heart-aortic trauma was investigated using live, anesthetized and postmortem canines subjected to frontal impact with a blunt impactor. The major focuses of this research program were: trauma to the heart aortic system, the kinematic response of the thoracic cage, and pressure in the ascending and descending aorta.

Head-to-knee interaction of the right front passenger dummy can occur in some 30-35 MPH crash barrier tests. The biofidelity and significance of these interactions as related to predicting human response was addressed in this study. In a series of laboratory experiments an instrumented headform was dropped on the dummy knee to simulate the barrier interactions. These test results were then related to the human by dropping the same headform on the cadaver leg. The instrumented headform was dropped from three heights to impact the Part 572 dummy knee at three velocities. Two impact sites and two impact angles were used. These test parameters bracketed the barrier conditions. Measurements from headform accelerometers permitted calculation of HIC value for comparison to barrier values. Comparable experiments were subsequently performed with three unembalmed cadaver subjects using the same headform and test procedures.