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Technical Paper

Fatal and Severe Injuries in Rear Impact; Seat Stiffness in Recent Field Accident Data

2008-04-14
2008-01-0193
A decade ago, James, et.al. published a detailed study of the available NASS data on severe rear impacts, with findings that “… stiffened or rigid seat backs will not substantially mitigate severe and fatal injuries in rear impacts.” No field accident study has since been advanced which refutes this finding. Advocates of rigidized seat backs often point to specific cases of severe rear impacts in which MAIS 4+ injuries are associated with seat back deformation, coupled with arguments supporting stiffer seatback designs. These arguments are generally based upon laboratory experiments with dummies in normal seating positions. Recent field accident data shows that generally, in collisions where the majority of societal harm is created, yielding seats continue to provide benefits, including those associated with whiplash associated disorders (WAD).
Technical Paper

Derivation of Vehicle-to-Vehicle Frontal Crash Pulse Estimates from Barrier Crash Data

2008-04-14
2008-01-0174
The BSAN crash pulse model has been shown to provide useful information for restraint sensing evaluation and for structural force-displacement studies in flat fixed rigid barrier (FFRB) crashes. This paper demonstrates a procedure by which the model may be extended for use with central and offset vehicle to vehicle (VTV) crashes through appropriate combinations of vehicle parameters.
Technical Paper

Pulse Shape and Duration in Frontal Crashes

2007-04-16
2007-01-0724
Understanding of events within the history of a crash, and estimation of the severity of occupant interior collisions depend upon an accurate assessment of crash duration. Since this time duration is not measured independently in most crash test reports, it must usually be inferred from interpretations of acceleration data or from displacement data in high-speed film analysis. The significant physical effects related to the crash pulse are often essential in reconstruction analyses wherein the estimation of occupant interior “second collision” or airbag sensing issues are at issue. A simple relation is presented and examined which allows approximation of the approach phase and separation phase kinematics, including restitution and pulse width. Building upon previous work, this relation allows straightforward interpretation of test data from related publicly available test reports.
Technical Paper

Occupant Injury in Rollover Crashes: A Reexamination of Malibu II

2007-04-16
2007-01-0369
The original Malibu II study, conducted by Bahling et al, found that neck compression loading in rollover crashes is caused by the occupant moving toward the ground and therefore, roof crush was not causally related to the loading. Some have disputed this finding claiming that the occupant does not “dive toward the roof,” but rather, the roof “moves in” toward the occupant, and that roof deformation is the primary cause of cervical spine injuries in rollover crashes. The original study included a detailed analysis of film and force transducer data for 10 Potentially Injurious Impacts (PII's). This paper presents an independent analysis of these 10 PII's and one additional PII. This analysis uses the film and transducer data to evaluate the timing of roof deformation and neck loading, the magnitude of roof deformation at the time of peak neck load, and the motion of the vehicle and occupants in the inertial reference system.
Technical Paper

Performance of Rear Seat Belt Restraints

2003-03-03
2003-01-0155
Field experience has consistently indicated that lap-only belts and lap-shoulder belts perform well and about equally in prevention of fatalities and serious injuries in the rear seating positions. Analyses based on overall usage and injury figures from the Fatal Analysis Reporting System (FARS), double-pair analysis of FARS data, and still older data bases have shown that, in the rear outboard seating positions, injury rates are about the same for lap-only and lap-shoulder belted crash occupants. Although sparse, recently available field data from the 1988-2001 National Analysis Sampling System / Crashworthiness Data System (NASS/CDS) files confirm the finding that, when used by rear seat occupants, lap-only belts perform about equally with lap-shoulder belts as countermeasures for serious and fatal injury in severe frontal crashes.
Technical Paper

Occupant Protection in Rear-end Collisions: II. The Role of Seat Back Deformation in Injury Reduction

1991-10-01
912914
The National Highway Traffic Safety Administration (NHTSA) has recently opened a rulemaking docket seeking comments on the design of automobile seats and their performance in rear Impacts. There are two philosophies of seat design: one advocates rigid seats, the other advocates seats which yield in a controlled manner. A review of the legislative history of seat back design standards indicates that yielding seats have historically been considered a better approach for passenger cars. The design characteristics of current production automobile seats are evaluated and show no significant changes over the past three decades. Concerns about the performance of rigid seat backs in real world rear impacts are discussed, specifically increased injury exposure due to ramping, rebound and out-of-position occupants.
Technical Paper

Force/Deflection and Fracture Characteristics of the Temporo-parietal Region of the Human Head

1991-10-01
912907
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.
Technical Paper

The Assessment of the Societal Benefit of Side Impact Protection

1990-02-01
900379
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.
Technical Paper

A Perspective on Side Impact Occupant Crash Protection

1990-02-01
900373
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.
Technical Paper

Crash Protection in Near-Side Impact - Advantages of a Supplemental Inflatable Restraint

1989-02-01
890602
Collision Safety Engineering, Inc. (CSE), has developed a test prototype system to protect occupants during lateral impacts. It is an inflatable system that offers the potential of improved protection from thoracic, abdominal and pelvic injury by moving an impact pad into the occupant early in the crash. Further, it shows promise for head and neck protection by deployment of a headbag that covers the major target areas of B-pillar, window space, and roofrail before head impact. Preliminary static and full-scale crash tests suggest the possibility of injury reduction in many real-world crashes, although much development work remains before the production viability of this concept can be established. A description of the system and its preliminary testing is preceded by an overview of side impact injury and comments on the recent NHTSA Rule Making notices dealing with side-impact injury.
Technical Paper

Facial Impact Response — A Comparison of the Hybrid III Dummy and Human Cadaver

1988-10-01
881719
Results indicate the need for a redesigned Hybrid III face capable of accurate force and acceleration measurements. New instrumentation and methods for facial fracture detection were developed, including the application of acoustic emissions. Force/ deflection information for the human cadaver head and the Hybrid III ATD were generated for the frontal, zygomatic, and maxillary regions.
Technical Paper

Interaction of Human Cadaver and Hybrid III Subjects with a Steering Assembly

1987-11-01
872202
Nineteen sled impact tests were conducted simulating a frontal collision exposure for an unrestrained driver. The deceleration sled buck configuration utilized the passenger compartment of a late model compact passenger vehicle, a rigid driver's seat, and a custom fabricated energy-absorbing steering column and wheel assembly. Sled impact velocities ranged from 24.1 to 42.6 km/hr. The purpose of the study was to investigate the kinematic and kinetic interaction of the driver and the energy-absorbing steering assembly and their relationship to the thoracic/abdominal injuries produced. The similarities and differences between human cadaver and anthropomorphic dummy subjects were quantified.
Technical Paper

A Repeated-Crash Test Technique for Assessment of Structural Impact Behavior

1986-02-24
860208
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.
Technical Paper

Crush Energy in Accident Reconstruction

1986-02-24
860371
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.
Technical Paper

A Load Sensing Face Form for Automotive Collision Crash Dummy Instrumentation

1986-02-24
860197
This paper summarizes the development of an Instrumented faceform which can record time histories of impact-related pressures at fifty-two locations over the entire face of a Hybrid 2 crash dummy skull. Pressures are measured by using piezo-electric, thin-plastic films; a high-speed, multiplex data acquisition system; signal conditioning; a software-controlled computerized data reduction and recording scheme; and a submergence calibration technique. The construction of the modified dummy face and the calibration gear are discussed. Examples of preliminary laboratory impact test results are presented. Theory and techniques relating to signal processing software, microprocessor controlled random-access-memory data-retrieval system and system calibration are also discussed. It is hoped that this tool, now undergoing final development and verification testing, will find extensive use in the evaluation and safety-related design of vehicle interiors and occupant restraints.
Technical Paper

Inaccuracies in the CRASHS Program

1985-02-25
850255
The CRASH3 computer program, a well known and useful tool in accident reconstruction, is shown to be innaccurate by comparison with car-to-car crash test data. Claims for accuracy of about 10 percent cannot be validated. Both the impact model and the damage only model yield results which are in error. Cases involving error well in excess of 20 percent are demonstrated. These inaccuracies are due primarily to the omission of terms in the formulation of the energy equation and to the sensitivity of the solution to the input estimate of principle-direction-of-force.
Technical Paper

The VTS Single-Vehicle Trajectory Simulation

1985-02-25
850252
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.
Technical Paper

A Perspective on Automobile Crash Fires

1985-02-25
850092
The relatively rare occurrence of injury or fatality in fuel-fed fires has received considerable attention in automotive safety rulemaking and products liability litigation. The literature related to fatalities associated with fire is confirmed by recent FARS data, and there are no reliable field data which confirm a need for further injury-reducing effect related to FMVSS 301. NHTSA has acknowledged this by removing crash fire rulemaking from its priorities plan. The police-reported crash fire data now available must be supplemented with in-depth investigation by trained teams before informed judgements can be made regarding further safety improvements with respect to crash fire injury.
Technical Paper

Design, Development and Testing of a Load-Sensing Crash Dummy Face

1984-02-01
840397
This project covers one facet of a program to develop a mechanical model for characterizing the time history of local forces on the zygomatic, maxillary and mandible regions of the human face during a frontal collision. Two mechanical devices to measure the forces on crash dummies during testing were designed, constructed and tested. The devices employed cantilever beams equipped with strain gauges. Both devices were subjected to a series of drop tests onto various materials. Time histories were compared to those obtained from cadaver experiments. While the data obtained from this testing appears to be similar to the cadaver data, further improvements and modifications will make the model much more useful.
Technical Paper

Injury and Intrusion in Side Impacts and Rollovers

1984-02-01
840403
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.
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