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Most rollover literature is statistical in nature, focuses on reconstructed field data and experiences, or utilizes a very broad pool of dissimilar test data. When test data is presented, nearly all of it involves hard surface rollover tests performed at speeds near 30 mph, with a mix of passenger cars, sport utility vehicles and minivans. Five full-scale dolly rollover tests on dirt of production sport utility vehicles (SUV) and multi-purpose vehicles (MPV) were performed with similar input parameters. The similarities included Federal Motor Vehicle Safety Standard (FMVSS) 208 rollover dolly initiated events, level dirt rollover surfaces, and initiation speeds over 40 mph. All tests were recorded with multiple high-speed and real-time cameras. Additionally, some of the tests included detailed documentation of the rollover surface and the resulting evidence and debris patterns, as well as onboard angular rate sensing instrumentation.

Recent cadaver studies have provided data for the development of force and stiffness characteristics of the side of the human head. A Hybrid III Anthropomorphic Test Dummy (ATD) head was modified to allow direct measurement of impact forces on the parietal and temporal regions by recasting the upper left half of the skull and installing triaxial piezoelectric force transducers. Dynamic impact tests of this modified head were conducted and force/stiffness characteristics for the temporal and parietal areas were compared to existing data on cadaver subjects. It was found that the existing Hybrid III vinyl skin satisfactorily represents the force/stiffness characteristics of the human head in these areas. This modified Hybrid III dummy head was also impacted against typical interior components likely to be contacted during a side impact. The force and acceleration test results are presented.

Much has been written about reconstruction techniques and testing methods concerning vehicle rollovers. To date, most of the literature describes rollovers as one-dimensional events. Rollovers account for a disproportionate fraction of serious injuries and fatalities among all motor vehicle accidents. The three-dimensional nature of rollover sequences in which a rolling vehicle experiences multiple ground contacts contributes to the environment where such injuries occur. An analytical technique is developed to model the airborne segments of a rollover sequence as a parabolic path of the vehicle center of gravity. A formulation for the center of gravity descent from maximum elevation to full ground contact is developed. This formulation contains variables that may be readily determined from a thorough reconstruction. Ultimately, this formulation will also provide a vertical ground impact velocity at contact.

Research focusing on automotive rollovers has garnered a great deal of attention in recent years. Substantial effort has been directed toward the evaluation of rollover resistance. Issues related to crashworthiness, such as roof strength and restraint performance, have also received a great deal of attention. Much less research effort has been directed toward a more detailed study of the rollover dynamics from point-of-trip to point-of-rest. The reconstruction of rollover crashes often requires a thorough examination of the events taking place between point-of-trip and point-of-rest. Increasing demands are placed on reconstructionists to provide greater levels of detail regarding the roll sequence. Examples include, but are not limited to, roll rates at the quarter-roll level, CG trajectory (horizontal and vertical), roll angle at impact, and ground contact velocity. Often the detail that can be provided in a rollover reconstruction is limited by a lack of physical evidence.

This paper presents a method of automobile collision analysis based on conservation of momentum. The analysis is applied to the collision of two two-dimensional bodies, either or both of which may be attached to a trailer. Newton's laws of motion are employed to determine changes in linear and angular velocities for the two-dimensional colliding bodies. Knowing the masses and rotational inertias and the initial velocities of all bodies at impact, the post-impact velocities can be calculated if appropriate constraints are applied to the bodies' post-collision motion. Various motion constraints, including lock-up, slip, and restitution are examined, and a methodology for modeling vehicle motion experienced during a collision is presented. The full set of basic equations characterizing this conservation-of-momentum analysis is presented with sufficient detail to allow their implementation on a programmable calculator or personal computer.

Accident data suggest that a significant percentage of rear impacts involve occupants seated in other than a “Normal Seated Position”. Pre-impact acceleration due to steering, braking or a prior frontal impact may cause the driver to move away from the seat back prior to impact. Nevertheless, virtually all crash testing is conducted with dummies in the optimum “Normal Dummy Seated Position”. A series of 7 rear impact sled tests, having a nominal AV of 21 mph, with Hybrid III dummies positioned in the “Normal Dummy Seated Position”, “Out of Position” and slightly “Out of Position” is presented. Tests were performed on yielding production Toyota and Mercedes Benz seats as well as on a much stiffer modified Ford Aerostar seat. Available Hybrid III upper and lower neck as well as torso instrumentation was used to analyze and compare injury potential for each set of test parameters.

Lean combustion in spark-ignition engines has long been recognized as a means of both improving engine efficiency and lowering carbon monoxide and oxides of nitrogen exhaust emissions. In this paper, the fundamentals of lean combustion are reviewed in terms of lean flammability and ignition, and lean misfire limit, from a compilation of research results. 125 references are included in the review. The effect of lean mixture on engine efficiency, performance and exhaust emissions is discussed. The effects of engine variables on lean combustion are presented, including mixture preparation, ignition, combustion chamber shape, compression rates and fuel additives. Techniques for lean burn engine control and emissions clean-up are also described.

Automobile racing engine performance has historically progressed with and aided the development of automotive technology. Racing engine performance has been improved in various applications with specialized liquid fuels, such as nitroparaffins, alcohol (methanol) and certain hydrocarbons used in racing gasolines. This paper presents physical and thermodynamic properties of commonly used racing fuels and selected additives, including nitrous oxide and hydrazine. Improving the antiknock properties of gasoline for racing purposes is also discussed. Engine operating characteristics and power output for each fuel are discussed in terms of appropriate fuel properties and engine parameters such as air/fuel ratio and compression ratio. Combustion of various fuels is discussed along with the effect of dissociation and heat loss on performance. Some experimental performance data are presented, and theoretical and practical considerations which effect fuel utilization are also discussed.

Single-cylinder engine tests, with computerized data aquisition, of several nitroparaffin and methanol fuel blends were conducted to identify engine operating conditions or fuel compositions which reduced combustion knock with no penalty to engine power. The effect of variation in equivalence ratio, nitromethane percentage in selected co-solvents, ignition timing and compression ratio was investigated at fixed engine speed and steady-state temperatures. Electronic filters were used to isolate the portion of the cylinder pressure signal containing combustion knock and a Fast Fourier Transform computer subroutine was used to characterize combustion severity in the frequency domain. The results verified the empirical racing engine practice that for a nitromethane/methanol mixture operating fuel-rich from stoichiometric, power is increased and knock is decreased.

The aerodynamic drag of rolling vehicles was studied by towing pairs of side-by-side identical small-scale models in rolling contact with the bottom of a water-filled trough. An instrumented towbar measured the difference in the models' overall drag forces in order to determine the effect of changes in a model's configuration on its aerodynamic drag. The effects of wheel-rim covers, axle fairings, and wheel-housing volume on vehicle drag were studied with the test apparatus. The magnitude of the effects were well outside the range of experimental error, and correlated well with published results of similar studies performed in wind tunnels. Testing indicated that lift-induced changes in vehicle rolling resistance would not significantly alter results of tow testing under normal circumstances. Advantages of the underwater tow test include the ability to inexpensively simulate rotating wheels and to study the interaction between rotating wheels on a moving vehicle and the ground plane.

An economical alternative technique is presented for obtaining vehicle frontal crush characteristics from a series of repeated low speed barrier crashes. Results were analyzed using a technique of linear correlation of residual crush depth with a defined crush energy parameter. The data compared closely with crashes reported in the literature, and suggested that the structure exhibits only a slight strain rate sensitivity. Crush energy is shown to correlate well with dynamic crush depth. Relations among dynamic and residual crush and recovery distance are reported, Velocity restitution is shown to be about constant at 15% over the impact velocity range employed. A force-deflection relation based on the offset force linear harmonic oscillator theory is suggested, shown to agree quite well with data. Repeated crash testing can be an effective method to obtain information needed for development of analytical and predictive tools useful in design and reconstruction.

The relationship between occupant crash injury and occupant compartment intrusion is seen in the perspectives of the velocity-time analysis and the NCSS statistical data for two important accident injury modes, lateral and rollover collisions. Restraint system use, interior impacts, and vehicle design features are considered. Side impact intrusion is analyzed from physical principles and further demonstrated by reference to staged collisions and NCSS data. Recent publications regarding findings of the NCSS data for rollovers, as well as the NCSS data itself, are reviewed as a background for kinematic findings regarding occupant injury in rollovers with roof crush.

A controlled experiment involving road marks was conducted to compare various photogrammetry practices currently in use in the accident investigation community. The experimental controls and results are discussed for three variations of one 2-D scheme and for six 3-D photogrammetric schemes applied to a similar set of road marks and points. For measurements related to the most frequent issues in traffic accidents, all of the methods are capable of providing usable data. The experimental photographs and corresponding data represent a reference set for developing skills and for comparison with other photogrammetry schemes.

Analytical reverse projection is introduced and is shown to offer an improvement in applicability and accuracy over other techniques of single-image photogrammetry, including plane-to-plane transformation and camera reverse-projection methods. A comparison of the methods is made on the basis of a single case of reconstructing missing tire tracks on a roadway intersection. Advantages and disadvantages of each method are discussed. THIS PAPER REVIEWS non-graphical techniques used to make measurements of features imaged in a single photograph. Two formulations of the plane-to-plane transformation method are re viewed, the camera reverse-projection technique is presented, and a third technique, called the analytical reverse-projection method, is introduced. Following a review of the various methods, including an indication of their advantages and disadvantages, each method is applied to the problem of relocating a set of tire tracks in an intersection.

The coefficient of restitution is an indicator of the elasticity of a collision. Restitution, or elastic rebound of a deformed surface, contributes to the change in velocity of collision partners, a common measure of injury severity in automobile collisions. Because of the complex nature of collisions between motor vehicles, the characterization of the expected magnitude of the coefficient in such collisions lacks detail and mechanisms influencing its value are not well understood. Using crash test data from the National Highway Traffic Safety Administration (NHTSA), this study investigates the expected magnitude of the coefficient of restitution and mechanisms influencing restitution in automobile collisions. Both vehicle-to-barrier and vehicle-to-vehicle tests are considered for all types of collisions. The influence of a variety of collision and vehicle parameters on restitution is also explored.

Among the several data recorded by a typical motor vehicle’s event data recorder (EDR) prior to, during and after a crash event, are sampled time histories of longitudinal and lateral components of delta-v. The delta-v components are not measured directly but are calculated by numerically integrating the outputs of two perpendicular accelerometers contained within the EDR box. As currently designed and implemented a typical EDR does not measure yaw velocity or track vehicle heading during the impulse phase of a crash. Without this yaw information to orient the accelerometers relative to the fixed ground, the delta-v values calculated by the EDR through direct integration of its measured acceleration components should not be interpreted as representing absolute changes in vehicle velocity, especially in cases where the yaw velocity is high. EDR-calculated delta-v components must be adjusted to account for the yaw motion that occurred during acquisition of the data.

The determination of appropriate friction coefficient values is an important aspect of accident reconstruction. Tire-roadway friction values are highly dependent on a variety of physical factors. Factors such as tire design, side force limitations, road surface wetness, vehicle speed, and load shifting require understanding if useful reconstruction calculations are to be made. Tabulated experimental friction coefficient data are available, and may be improved upon in many situations by simple testing procedures. This paper presents a technical review of basic concepts and principles of friction as they apply to accident reconstruction and automobile safety. A brief review of test measurement methods is also presented, together with simple methods of friction measurement to obtain more precise values in many situations. This paper also recommends coefficient values for reconstruction applications other than tire- roadway forces.