Occupant Restraint System Research Articles

Study on the Difference of Frontal Impact Response among People of Different Sizes

In this article, seven frontal impact simulation models with same restraint system and different human body models were established through the use of multi-body kinematics software MADYMO. The injuries in head, chest and femurs of different human models and the differences of these injuries were analyzed in detail. The weighted injury criterion was adopted to evaluate the overall injuries of different human body models. The results shows that the injury risk of smaller human body is much higher than the taller human body, and existing occupant restraint system that protects the 50th percentile American occupant well protects other size occupant poorly.

Data mining application on crash simulation data of occupant restraint system

This article presents an application of data mining method on finite element data and crashworthiness result data of an occupant restraint system. According to the characteristics of the CAE (Computer-Aided Engineering) data, a framework for data preparation is developed based on object-oriented programming concepts. Training sets are built from data recorded in 98 crash simulations that adhere to FMVSS208, the America occupant crash protection testing standard. Relationship between design parameters and system effectiveness is implied in these data sets. Decision tree using C4.5 algorithm and attribute selection method based on attribute’s estimated importance are introduced to perform data mining on the building of training sets. The result yielded by data mining endows us with a deeper insight into the interrelations between the key design parameters and the performance of the occupant restraint system in crash simulations. Finally, the learned rules are tested on the real crash simulation data sets. The result of the testing shows that these rules are proper, and can been used as a guidance for the design of the occupant restraint system.

Wheelchair tiedown and occupant restraint loading associated with adult manual transit wheelchair in rear impact

Proper securement of wheelchairs in motor vehicles is vital to providing wheelchair users an adequate level of safety in a crash. Thus far, wheelchair tiedown and occupant restraint systems (WTORS) loading has mostly been examined under frontal impact conditions. Because of the inherent crash dynamic differences, rear-impact loading of WTORS is expected to differ greatly. In this study, three identical, reinforced, manual, folding, X-braced ANSI/RESNA WC19 wheelchairs were subjected to an International Organization for Standardization-proposed rear-impact crash pulse. WTORS loads (front tiedowns, rear tiedowns, lap belt, and shoulder belt) were measured and compared with frontal impact WTORS loading. Rear impact produced substantially higher loads (up to 7,851 N) in the front tiedowns than frontal impact. The rear tiedowns experienced relatively negligible loading (up to 257 N) in rear impact, while rear-impact dynamics caused the lap belt (maximum load of 1,865 N) to be loaded substantially more than the shoulder belt (maximum load of 68 N). Considering differences in frontal and rear impact WTORS loading is important to proper WTORS design and, thus, protection of wheelchair-seated occupants subjected to rear-impact events.

Robustness Design of Occupant Restraint System Based on Kriging Model

Design variables have some uncertainties during the design process of occupant restraint system.Conventional optimization design,however,neglects uncertainties,it always leads to optimal object beyond constraints or object function very sensitive to the fluctuation of design variables,thus resulting in design failure.Aiming at a minibus,by means of the occupant injury analysis software,a simulation model of occupant restraint system for frontal impact of the minibus is built and the verification of the model is carried out.Based on the model,through the applications of experimental design,Kriging models and Monte Carlo simulation technique,a 6σ robustness optimization method based on product quality engineering is constructed.The method not only searches the optimum results for the design object,but also improves the reliability of the design parameters and the robustness of objective function.Engineering example indicates this method has stronger engineering practicability in the design of occupant restraint system.

Orion Crew Member Injury Predictions during Land and Water Landings

A review of astronaut whole body impact tolerance is discussed for land or water landings of the next generation manned space capsule named Orion. LS-DYNA simulations of Orion capsule landings are performed to produce a low, moderate, and high probability of injury. The paper evaluates finite-element (FE) seat and occupant simulations for assessing injury risk for the Orion crew and compares these simulations to whole body injury models commonly referred to as the Brinkley criteria. The FE seat and crash dummy models allow for varying the occupant restraint systems, cushion materials, side constraints, flailing of limbs, and detailed seat/occupant interactions to minimize landing injuries to the crew. The FE crash test dummies used in conjunction with the Brinkley criteria provides a useful set of tools for predicting potential crew injuries during vehicle landings.

Characterization of pediatric wheelchair kinematics and wheelchair tiedown and occupant restraint system loading during rear impact

This study characterizes pediatric wheelchair kinematic responses and wheelchair tiedown and occupant restraint system (WTORS) loading during rear impact. It also examines the kinematic and loading effects of wheelchair headrest inclusion in rear impact. In two separate rear-impact test scenarios, identical WC19-compliant manual pediatric wheelchairs were tested using a seated Hybrid III 6-year-old anthropomorphic test device (ATD) to evaluate wheelchair kinematics and WTORS loading. Three wheelchairs included no headrests, and three were equipped with slightly modified wheelchair-mounted headrests. Surrogate WTORS properly secured the wheelchairs; three-point occupant restraints properly restrained the ATD. All tests used a 26 km/h, 11 g rear-impact test pulse. Headrest presence affected wheelchair kinematics and WTORS loading; headrest-equipped wheelchairs had greater mean seatback deflections, mean peak front and rear tiedown loads and decreased mean lap belt loads. Rear-impact tiedown loads differed from previously measured loads in frontal impact, with comparable tiedown load levels reversed in frontal and rear impacts. The front tiedowns in rear impact had the highest mean peak loads despite lower rear-impact severity. These outcomes have implications for wheelchair and tiedown design, highlighting the need for all four tiedowns to have an equally robust design, and have implications in the development of rear-impact wheelchair transportation safety standards.

Development and validation of a computer crash simulation model of an occupied adult manual wheelchair subjected to a frontal impact

Wheelchairs are primarily designed for mobility and are not necessarily intended for use as motor vehicle seats. However, many wheelchairs serve as vehicle seats for individuals unable to transfer to a vehicle seat. Subjecting wheelchairs to sled testing, in part establishes the crashworthiness of wheelchairs used as motor vehicle seats. Computer simulations provide a supplemental approach for sled testing, to assess wheelchair response and loading under crash conditions. In this study a nonlinear, dynamic, computer model was developed and validated to simulate a wheelchair and occupant subjected to a frontal impact test (ANSI/RESNA WC19). This simulation model was developed utilizing data from two frontal impact 20 g/48 km/h sled tests, which consisted of identical, adult manual wheelchairs secured with 4-point tiedowns, occupied with a 50th percentile adult male anthropomorphic test device (ATD), restrained with a 3-point occupant restraint system. Additionally, the model was validated against sled data using visual comparisons of wheelchair and occupant kinematics, along with statistical assessments of outcome measures. All statistical evaluations were found to be within the acceptance criteria, indicating the model's high predictability of the sled tests. This model provides a useful tool for the development of crashworthy wheelchair design guidelines, as well as the development of transit-safe wheelchair technologies.

Analysis on the Influence for the Protection on Frontal Impact by Vehicle Seat Cushion Obliquity

An assumption is brought, that is, by using seat cushion to make effective restraint in front of occupants’ center of gravity, and adding seat cushion obliquity adjusting instrument to increase the angle between seat cushion and floor of car body before or during front collision, occupants’ injury can be reduced. Therefore, based on the correlation size of a certain car and performance parameter of driving region, MADYMO analysis software is used to establish the simulation model of automobile front collision, and which is verified by tests. After simulation analysis by using different seat cushion obliquity, the result indicates that when 25° tilting angle of seat cushion is used, head injury declines 21.4% , chest injury drops 16.6% , but hip trauma only increases 8.2% , and the leg wound is still low. That is to say, adding seat cushion obliquity adjusting instrument in Occupant Restraint System can effectively reduce occupants’ injury.

Transportation Safety Standards for Wheelchair Users: A Review of Voluntary Standards for Improved Safety, Usability, and Independence of Wheelchair-Seated Travelers

Safe transportation for wheelchair users who do not transfer to the vehicle seat when traveling in motor vehicles requires after-market wheelchair tiedown and occupant restraint systems (WTORS) to secure the wheelchair and provide crashworthy restraint for the wheelchair-seated occupant. In the absence of adequate government safety standards, voluntary standards for the design and performance of WTORS, and for wheelchairs used as seats in motor vehicles, have been developed. The initial versions of these standards qualify equipment for use in all types and sizes of motor vehicles using a 30-mph (48-kph), 20-g frontal sled-impact test. The wheelchair standard requires four accessible, crash-tested securement points on wheelchairs so they can be more easily and effectively secured using a four-point strap-type tie-down system. Future voluntary standards are aimed at reducing injury risk for wheelchair-seated occupants in rear impacts and at providing a method for evaluating the crashworthiness of wheelchair seating systems independent of wheelchair base-frames. They also address improved usability and independence for wheelchair-seated travelers using public transportation by specifying universal docking interface geometry for wheelchairs and design and performance requirements for rear-facing wheelchair passenger stations for use in the very low-g environments of large fixed-route transit buses.

Occupant Restraint Preferences of Individuals Traveling in Motor Vehicles While Seated in Their Wheelchairs

A survey among 127 wheelchair users was conducted to characterize wheelchair occupant restraint usage patterns, restraint deficiencies, user characteristics, and essential wheelchair occupant restraint design parameters for when individuals travel in motor vehicles while seated in their wheelchairs. Survey respondents value independent travel and seem generally interested in the use of an occupant restraint system that is attached to the wheelchair frame and that can be used independently by the wheelchair user without caregiver or vehicle driver assistance. Results of the survey further indicate that despite the relatively high percentage of respondents who are attempting to travel safely (78.8%), almost half of these wheelchair users have experienced injury or compromised wheelchair balance while traveling in motor vehicles.

Child Passenger Safety: Direction, Selection, Location, Installation

The most significant risk factor for death and serious injury in a car crash is the failure to use a size-appropriate restraint system. Providing accurate car safety seat anticipatory guidance to families is the standard of care. Guiding families on the best car seat for best protection can be done with the four messages, direction, selection, location, and refer, if needed, to community resources for correct installation. Addressing special issues that impact use of a car seat on each and every ride, including challenging behaviors and obesity, will transfer to many other situations. Data support a new recommendation that children stay rear-facing in size-appropriate car seats until they reach the highest weight and height allowed for rear-facing by the manufacturer of the convertible seat. Premature graduation to the next seat type/size/position increases risk of injury. A driver who is distracted by a cell phone, food, or something else, becomes a risk factor for a car crash. State laws may lag behind best practices. Advocacy for stronger laws, better enforcement, and best practices at the local, state, and national levels is a critical role for the pediatric professional community.

A two-stage multi-objective optimisation of vehicle crashworthiness under frontal impact

Crashworthiness is one of the most important criteria in vehicle design, which often requires large-scale design analysis for a full-vehicle model consisting of many structural parts and special safety elements. The design typically involves a large number of design variables and sometimes leads to a prohibitively high computing cost. To solve this problem, this paper presents a two-stage procedure to cope with crashworthiness design of a structural frame and occupant restraint system. In the first stage, a multi-objective optimisation is carried out for structural parameters in the frontal parts without considering the details of the occupant restraint device. In the second stage, the parameters of the occupant restraint system are optimised based on an optimised structure system. In these two stages, explicit finite element and multi-body dynamics methods are employed to respectively construct response surface and Kriging model with various designs-of-experiment techniques. A full-scale vehicle model is developed to demonstrate the capability of the present two-stage design method.

Influence of occupant restraint system on traumatic brain injuries

The influence of occupant restraint system on traumatic brain injuries in a front crash was computationally investigated using multibody and finite element methods in a loosely-coupled manner. A multibody dynamic analysis that includes a crash dummy and vehicle model with/without restraint system was performed. Based on the kinematic characteristics of the dummy's head obtained from the multibody dynamic analysis, two different finite element analyses with a human head model were performed. The first approach was simply to drive the finite element head model with an initial velocity and deceleration calculated from the multibody analysis. The second approach was to reconstruct the complicated crash scenario using simple head impact to a stationary wall, in which the head yielded almost identical kinematic characteristics obtained from the multibody analysis. Through the two approaches, strain-, pressure-, and motion-based brain injury metrics were assessed for three different settings of occupant restraint system.

A new optimisation approach for the driver restraint system for the frontal impact of a mini-bus

Occupant restraint system design is very important for passenger vehicles to improve passive safety performance. In this paper, an optimisation approach using MADYMO simulation is put forward for occupant restraint system design. Based on multi-body dynamics theory and the finite element method, an occupant restraint system model is built for the driver protection in a mini-bus subject to frontal impact. The model validation is also considered against the full size impact test. Then, a new parameter optimisation approach, called the three-step optimisation method, is proposed and applied to the model established. Simulations are conducted to investigate the system performance. The results indicate significant safety performance improvements for the mini-bus occupant restraint system.

Wheelchair Tiedown and Occupant Restraint System Issues in the Real World and the Virtual World: Combining Qualitative and Quantitative Research Approaches

The Americans with Disabilities Act requires that transit providers accommodate passengers who use “common wheelchairs” when traveling in a motor vehicle. Wheelchair tiedown and occupant restraint systems are commonly used to secure wheelchairs and restrain occupants in fixed-route and demand route transit vehicles. Throughout the 17 years since the Americans with Disabilities Act has been in effect, transit providers have complained about the usability of wheelchair tiedown and occupant restraint systems, and improper securement has been linked to injuries among wheelchair users during “nonimpact incidents.” This research study explored the use of wheelchair tiedown and occupant restraint systems in actual practice and the potential risks of misuse to wheelchair-seated individuals. The qualitative research conducted in this study revealed that improper wheelchair securement (i.e. using less than four tiedown straps) can be fairly common practice in fixed-route transit. In addition, preliminary computer simulations show that improper wheelchair securement in emergency driving conditions may place wheelchair occupants at a greater risk of injury. It should be noted, however, that this is a pilot study and has its limitations. For example, qualitative data were gathered from one metropolitan area transit provider across a limited range of vehicle and wheelchair types. Additionally, the computer simulation model used in this study was originally validated for impact situations.

Riding a Bus While Seated in a Wheelchair: A Pilot Study of Attitudes and Behavior Regarding Safety Practices

A total of 283 wheelchair-seated bus riders responded to a 35-item Web-based survey investigating their experiences on public, fixed-route buses. The survey addressed the use of wheelchair tiedowns and occupant restraint systems (WTORS), the attitudes and behaviors of wheelchair users toward the use of this equipment, and the transit experience. Results indicate that consistent use of four-point tiedown and occupant restraint systems is fairly low. Only 33.2% of the participants reported always securing their wheelchair, and 62.2% reported using occupant restraints consistently. A preference for fixed-route over paratransit was related to larger city size. Implementation of transit agency policy regarding WTORS was found to be inconsistent. Easier-to-use WTORS and improved operator training in larger transit agencies would likely increase the correct use of safety equipment and improve wheelchair users' bus-riding experiences.

Human Factors Evaluation of Restraint Systems for Military Vehicles

Three configurations of occupant restraint systems were evaluated for use in military vehicles. Restraint configurations consisted of a 23 (lap and two shoulder belts), 3+2 (standard 3-point lap/shoulder belt plus secondary shoulder belt) and 5-point (two shoulder, two lap, and one crotch belt). All systems had a single point release feature. Human factors evaluation entailed assessing ingress/egress, functional operation (control reach) and accommodation (fit). Testing included with and without full gear. Eleven soldiers with military vehicle driving experience participated in the evaluation. Results for egress testing showed that the 5-point was slightly faster than the 3+2 and the 23. Results for the ingress testing showed that ingress time was directly related to the number of connections with the 3+2, 23 and the 5-point reflecting fastest to slowest times. Wearing full gear significantly increased ingress time but had minimal effects on egress times. No major accommodation issues were noted.

Renal Injury Mechanisms of Motor Vehicle Collisions: Analysis of the Crash Injury Research and Engineering Network Data Set

Injury prevention requires efficient diagnosis and management, and knowledge of collision kinematics may allow first responders to triage victims earlier based on crash scene assessment. We identified possible collision patterns and vehicle interior components that may have a role in kidney injury following motor vehicle collision. A total of 115 cases (131 renal injuries) were identified in the multicenter Crash Injury Research and Engineering Network database. For each case a crash investigation was performed, identifying vehicle kinematic characteristics, vehicle damage profile and an assessment of the interior compartment to determine points of occupant contact and restraint system use. A multidisciplinary team reviewed each case to establish a probable mechanism for all injuries sustained. Review of the medical record was performed to identify subject demographics and injury characteristics. Cases were analyzed based on frontal vs side impact. Of the subjects 52% were male. Mean age was 36.1 years and median injury severity score was 33. Overall injuries were low grade in 72.5% of patients, 30% were unrestrained and 47.6% of collisions were side impact. No difference was observed between frontal and lateral collisions with respect to renal injury severity. For frontal impact the seat belt was the source in 26 of 29 renal injuries (90%) and 12 of 15 unrestrained cases (80%) were due to direct impact with the steering column. Of 131 side impact injuries 62 were attributable to impact with lateral compartment elements. Side impact injuries were associated with lateral door panel impact (41 of 61) with the armrest accounting for 22. The mean lateral compartment intrusion was 29.6 cm. No grade V injuries occurred when vehicle intrusion was less than 30 cm. The mean change in velocity for frontal and lateral collisions was 24.0 and 31.5 mph, respectively (p <0.05). In frontal collisions the change in velocity for kidney injuries sourced to the steering wheel vs seat belt injuries was statistically greater (41.5 vs 28.4 mph, p = 0.05). Renal injury in frontal and side impact collisions appears to occur after direct impact from objects in the vehicle compartment. For frontal crashes occupant acceleration into the seat belt or steering wheel seems to result in renal injuries. Side impact injuries occur when the vehicle side panel intrudes into the compartment, striking the occupant. Further collision evaluation in larger data sets is required to substantiate our findings.

Trends in Crash Detection and Occupant Restraint Technology

In the past two decades, occupant restraint systems for automobiles have made considerable progress globally. There has been a tremendous increase in the complexity and sophistication of functional requirements. Particularly significant in the overall evolution of restraint systems is the growth in electronics content, which is concurrent with similar phenomena in the automotive world, as well as in many other technology-related fields. In conjunction with this trend, the shift to digital components and subsystems expanded, while the design of restraint systems has become more diversified with enhanced adaptability and flexibility. In addition to the airbags that are standardized for passenger vehicles, there has been a whole spectrum of emerging safety features that provide additional safety improvements. For example, rollover and occupant sensing are being added onto an integrated occupant protection system. Global positioning systems are coupled with crash sensors into emergency notification services. Increasingly, vehicles are now being equipped with active safety systems. The availability of both passive restraints and active safety functions will allow an additional layer of synergistic integration across safety systems. Research and developments in vehicular safety can be expected to remain active in the foreseeable future. This paper describes the system-level design trends that have occurred in the past and offers a perspective of future design transition in automotive restraint systems

Motor Vehicle Restraint System Use and Risk of Spine Injury

Objective. Motor vehicle collision (MVC)-related spinal injury is a severe and often permanently disabling injury. In addition, strain injuries have been reported as a common outcome of MVCs. Although advances in automobile crashworthiness have reduced both fatalities and severe injuries, the impact of varying occupant restraint systems (seatbelts and airbags) on thoracolumbar spine injuries is unknown. This study examined the relationship between the occurrence of mild to severe cervical and thoracolumbar spine injury and occupant restraint systems among front seat occupants involved in frontal MVCs. Methods. A retrospective cohort study was conducted among subjects obtained from the 1995–2004 National Automotive Sampling System. Cases were identified based on having sustained a spine injury of ≥1 on the Abbreviated Injury Scale (AIS), 1990 Revision. Risk risks (RRs) and 95% confidence intervals (CIs) were computed comparing occupant restraint systems with unrestrained occupants. Results. We found an overall incidence of AIS1 cervical (11.8%) and thoracolumbar (3.7%) spinal injury. Seatbelt only restraints were associated with increased cervical AIS1 injury (RR = 1.40, 95% CI 1.04–1.88). However, seatbelt only restraints showed the greatest risk reduction for AIS2 spinal injuries. Airbag only restraints reduced thoracolumbar AIS1 injuries (RR = 0.29, 95% CI 0.08–1.04). Seatbelt combined with airbag use was protective for cervical AIS3+ injury overall (RR = 0.29, 95% CI 0.14–0.58), cervical neurological injury (RR = 0.19, 95% CI 0.05–0.81), and thoracolumbar AIS3+ injury overall (RR = 0.20, 95% CI 0.05–0.70). Conclusions. The results of this study suggest that seatbelts alone or in combination with an airbag increased the incidence of AIS1 spinal injuries, but provide protection against more severe injury to all regions of the spine. Airbag deployment without seatbelt use did not show increased protection relative to unrestrained occupants.