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Snowmobile acceleration, braking and cornering performance data are not well developed for use in accident reconstruction. Linear acceleration and braking data published by D'Addario[1] gives results for testing on 4 snowmobiles of various make and model. This paper presents the results of on-snow tests performed in 2014 which include acceleration and cornering maneuvers that have not been published previously. Maximum and average cornering speeds and corresponding lateral accelerations are presented for turns of radius 20, 35 and 65 feet (6.1, 10.7 and 19.8 meters) on level, packed snow. Performance values for acceleration, braking, and cornering are determined in tests with and without a passenger. Results of linear acceleration and braking tests were found to be comparable to the previously published work. The data are useful in snowmobile accident reconstruction for certain types of snowmobile motion analyses.

Recent detailed field accident data are examined with regard to injuries associated with rear impacts. The distribution of “Societal Harm” associated with various injury mechanisms is presented, and used to evaluate the performance of current seat back and restraint system designs. Deformation associated with seat back yield is shown to be beneficial in reducing overall Societal Harm in rear impacts. The Societal Harm associated with ejection and contact with the vehicle rear interior (the two injury mechanisms addressed by a rigid seat approach), is shown to be minimal. The field accident data also confirm that restraint usage in rear impacts has a substantial injury-reducing effect. Laboratory tests and computer simulations were run to investigate the mechanism by which seat belts protect occupants in rear impacts.

In reconstruction of on-roadway vehicle accidents, roadway surface gouges and the forces and energy attributed to the related vehicle components become important keys to resolving accurate accident reconstructions. Accounting for the forces applied to vehicle components and the energy dissipated from such forces can be helpful where supporting data exists. Roadway gouge forces vary depending upon such factors as road surface temperature and the velocity of the gouging mechanism. Other factors that may affect roadway gouges are road surface age, differing gouge tooth geometry, and road surface construction but these factors are not addressed in this paper. Calculation and summation of individual contact forces and contact energies can be significant in the accounting of accident vehicle motion reconstruction. This paper expands upon findings presented in SAE 2008-01-0173.

Development of a seat with an active adjustable seatback stiffness for enhanced safety during a rear impact is demonstrated. Review of literature suggests that there is not a single value for seatback stiffness to optimize occupant protection. An automobile seat whose stiffness can be actively adjusted based on EDR input and other factors can potentially enhance occupant safety during some rear impact crashes. Static pull tests were performed using a prototype seat demonstrating how seatback stiffness can be modified, and deformation limited, using electromechanical means. Research and development of this technology is ongoing.

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.

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.

This paper presents results of full-scale instrumented rollover testing on ROV type recreational vehicles. Five tests were conducted using two instrumented side-by-side ROVs at speeds between 20 and 32 mph on unpaved surfaces. Each test vehicle was brought to speed and released, allowing remote steering inputs to initiate turn sequences resulting in rollover. Accelerations were determined using x, y, and z axis accelerometers mounted at the vehicle CG and recorded using a robust data acquisition system. Roll rates were measured using a rotation rate sensor. Roll rates and key acceleration events are presented for each test. Mapping and measurement of the test site includes photography and digital survey of resulting tire marks, impact marks and gouging. Documentation and reconstruction of test roll sequences includes roll rates, vehicle positions and velocities, peak accelerations by impact, and scratch mark and damage examination. These are included in the appendix .

Rollover crashes involving side-by-side ATVs and injuries related to these crashes represent an increasing percentage of the total population of ATV injury crashes. Unlike traditional ATVs, side-by-side ATVs are designed to carry two passengers abreast and usually include roll bars and seat belts. Most side-by-side ATVs are also designed to carry a limited payload in a rear cargo bed. Primary target uses for these vehicles include a combination of utilitarian tasks and recreational activities. Modifications by consumers often incorporate additional equipment that can change the mass balance and handling characteristics of the vehicle. This paper explores the resistance of these vehicles to roll as affected by the variables commonly applied to automotive crashes. Static Stability Factor (SSF) and Critical Sliding Velocity (CSV) are calculated and compared to findings from previously published work on roll resistance.

Impact tests were conducted on thirty-one unembalmed human cadaver heads. Impacts were delivered to the temporo-parietal region of fixed cadavers by two, different sized, flat-rigid impactors. Yield fracture force and stiffness data for this region of the head are presented. Impactor surfaces consisted of a 5 cm2 circular plate and a 52 cm2 rectangular plate. The average stiffness value observed using the circular impactor was 1800 N/mm, with an average bone-fracture-force level of 5000 N. Skull stiffness for the rectangular impactor was 4200 N/mm, and the average fracture-force level was 12,500 N.

Gouges and scratches to rollover protection structures are informative to the reconstruction and analysis of real-world vehicle rollover crashes. Variations in ground surface composition can be correlated with accompanying witness marks on the vehicle rollover protection structure. This paper presents the results of rollover protection structure specimen tests using a variety of test speeds and surface compositions. The test results and analyses that follow are displayed for use in comparison to similar damage on subject crash vehicles. In addition, impact of steel rollover protection structures with various opposing ground surface materials can produce visible sparks in low light conditions. Tests were performed to show the ability of these structures to produce sparks from various surface impacts.

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.

The NHTSA notices of proposed rulemaking on side impact protection have focused worldwide attention on one of the most difficult and frustrating efforts in automobile crash safety. Traditional vehicle design has evolved obvious structural contrasts between the side of the struck vehicle and the front of the striking vehicle. Protection of near-side occupants from intruding door structure is a most perplexing engineering challenge. Much useful and insightful engineering work has been done in conjunction with NHTSA's proposed rulemaking. However, there are many major engineering issues which demand further definition before reasonable side impact rulemaking test criteria can be finalized. This paper reviews recent findings which characterize the human factors, biomechanics, and occupant position envelope of the typical side impact crash victim.