Investigation of wheelchair instability during transport in large accessible transit vehicles

Large accessible transit vehicles (LATVs, fixed-route intracity buses), generally considered safe, may not be as safe for wheelchair-seated passengers. Transit provider practices vary regarding use of wheelchair tiedown and occupant restraint systems (WTORSs), while recent research suggests high levels of WTORS disuse and misuse. We sought to better understand wheelchair and wheelchair passenger instabilities related to WTORS disuse and misuse on LATVs. This article presents a retrospective review of 295 video surveillance records of wheelchair passenger trips on LATVs. Wheelchair trips involving disuse and misuse of WTORS were quantified and categorized based on WTORS configurations. Cases of wheelchair and wheelchair passenger instability were categorized based on severity, type, and direction. Three adverse events involving severe wheelchair and/or passenger instability were examined in greater detail. Results showed 20.3% of records involved wheelchair-related adverse events (95% minor instabilities, 5% severe instabilities). Scooters were most likely to be unstable, followed by manual and power wheelchairs. In most instability cases, no tiedowns were used to secure the wheelchair and no lap belt was used to restrain the wheelchair passenger properly. In many instances, the lap belt was misused in an attempt to secure the wheelchair, whereas the shoulder belt was never used.

Assessment of injury potential in pediatric bed fall experiments using an anthropomorphic test device

Falls from beds and other furniture are common scenarios provided to conceal child abuse but are also common occurrences in young children. A better understanding of injury potential in short-distance falls could aid clinicians in distinguishing abusive from accidental injuries. Therefore, this study investigated biomechanical outcomes related to injury potential in falls from beds and other horizontal surfaces using an anthropomorphic test device representing a 12-month-old child. The potential for head, neck, and extremity injuries and differences due to varying impact surfaces were examined. Linoleum over concrete was associated with the greatest potential for head and neck injury compared to other evaluated surfaces (linoleum over wood, carpet, wood, playground foam). The potential for severe head and extremity injuries was low for most evaluated surfaces. However, results suggest that concussion and humerus fracture may be possible in these falls. More serious head injuries may be possible particularly for falls onto linoleum over concrete. Neck injury potential in pediatric falls should be studied further as limitations in ATD biofidelity and neck injury thresholds based solely on sagittal plane motion reduce accuracy in pediatric neck injury assessment. In future studies, limitations in ATD biofidelity and pediatric injury thresholds should be addressed to improve accuracy in injury potential assessments for pediatric short-distance falls. Additionally, varying initial conditions or pre-fall positioning should be examined for their influence on injury potential.

RESNA's position on wheelchairs used as seats in motor vehicles

This position paper is based on the premise that those who ride seated in wheelchairs are entitled to equivalent occupant safety when they are traveling in motor vehicles. The document summarizes research and best practice for safety and selection of crashworthy wheelchairs with the requisite features required by the WC19 safety standard when it is necessary for individuals to use a wheelchair as a seat in a motor vehicle. Recommendations are based on data from accident and injury databases, prior research and a synopsis of the design, testing, performance and labeling requirements of ANSI and ISO voluntary industry standards for wheelchair transportation safety. This paper is intended for an audience of consumers, rehabilitation and health care professionals, manufacturers of wheelchairs and wheelchair transportation equipment and those who make reimbursement and public policy decisions.

Wheeled mobility device transportation safety in fixed route and demand-responsive public transit vehicles within the United States

An overview of the current status of wheelchair transportation safety in fixed route and demand-responsive, non-rail, public transportation vehicles within the US is presented. A description of each mode of transportation is provided, followed by a discussion of the primary issues affecting safety, accessibility, and usability. Technologies such as lifts, ramps, securement systems, and occupant restraint systems, along with regulations and voluntary industry standards have been implemented with the intent of improving safety and accessibility for individuals who travel while seated in their wheeled mobility device (e.g., wheelchair or scooter). However, across both fixed route and demand-responsive transit systems a myriad of factors such as nonuse and misuse of safety systems, oversized wheeled mobility devices, vehicle space constraints, and inadequate vehicle operator training may place wheeled mobility device (WhMD) users at risk of injury even under non-impact driving conditions. Since WhMD-related incidents also often occur during the boarding and alighting process, the frequency of these events, along with factors associated with these events are described for each transit mode. Recommendations for improving WhMD transportation are discussed given the current state of

Pediatric short-distance household falls: biomechanics and associated injury severity

OBJECTIVES

Short-distance household falls are a common occurrence in young children, but are also a common false history given by caretakers to conceal abusive trauma. The purpose of this study was to determine the severity of injuries that result from accidental short-distance household falls in children, and to investigate the association of fall environment and biomechanical measures with injury outcomes.

METHODS

Children aged 0-4 years who presented to the Emergency Department with a history of a short furniture fall were included in the study. Detailed case-based biomechanical assessments were performed using data collected through medical records, interviews, and fall scene investigations. Injuries were rated using the Abbreviated Injury Scale (AIS). Each case was reviewed by a child abuse expert; cases with a vague or inconsistent history and cases being actively investigated for child abuse were excluded.

RESULTS

79 subjects were enrolled in the study; 15 had no injuries, 45 had minor (AIS 1) injuries, 17 had moderate (AIS 2) injuries, and 2 had serious (AIS 3) injuries. No subjects had injuries classified as AIS 4 or higher, and there were no fatalities. Children with moderate or serious injuries resulting from a short-distance household fall tended to have fallen from greater heights, have greater impact velocities, and have a lower body mass index than those with minor or no injuries.

CONCLUSION

Children aged 0-4 years involved in a short-distance household fall did not sustain severe or life-threatening injuries, and no children in this study had moderate or serious injuries to multiple body regions. Biomechanical measures were found to be associated with injury severity outcomes in short-distance household falls. Knowledge of relationships between biomechanical measures and injury outcomes can aid clinicians when assessing whether a child's injuries were the result of a short-distance fall or some other cause.

Injury biomechanics and child abuse

Child abuse is a leading cause of morbidity and mortality in young children and infants in the United States. Medical care providers, social services, and legal systems make critical decisions regarding injury and history plausibility daily. Injury plausibility judgments rely on evidence-based medicine, individualized experiences, and empirical data. A poor outcome may result if abuse is missed or an innocent family is accused, therefore evidence and science-based injury assessments are required. Although research in biomechanics has improved clinical understanding of injuries in children, much work is still required to develop a more scientific, rigorous approach to assessing injury causation. This article reviews key issues in child abuse and how injury biomechanics research may help improve accuracy in differentiating abuse from accidental events. Case-based biomechanical investigations, human surrogate, and computer modeling biomechanics research applied to child abuse injury are discussed. The goal of this paper is to provide an overview of key research studies rather than on review or commentary articles. Limitations and future research needs are also reviewed.

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.

State of the science workshop on wheelchair transportation safety

The Rehabilitation Engineering Research Center on Wheelchair Transportation Safety held a state-of-the-science workshop on wheelchair transportation. The workshop had three purposes: reviewing and documenting the status of wheelchair transportation safety, identifying deficiencies, and formulating, discussing, and prioritizing recommendations for future action. The final goal was to disseminate the workshop outcomes for utilization in formatting future research priorities. A nominal group technique was used to facilitate focused open discussion by knowledgeable persons, resulting in the identification and ranking of existing deficiencies according to priority. Participants then formulated potential short-term solutions and speculated what wheelchair transportation safety should be in the future. This document presents four white papers, prepared prior to the workshop and modified according to participant feedback, and summarizes the outcomes of the workshop. The results identify and prioritize recommendations for future action.

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 26km/h, 11g 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.

Annual risk of death resulting from short falls among young children: less than 1 in 1 million

OBJECTIVE

The objective of the work was to develop an estimate of the risk of death resulting from short falls of <1.5 m in vertical height, affecting infants and young children between birth and the fifth birthday.

METHODS

A review of published materials, including 5 book chapters, 2 medical society statements, 7 major literature reviews, 3 public injury databases, and 177 peer-reviewed, published articles indexed in the National Library of Medicine, was performed.

RESULTS

The California Epidemiology and Prevention for Injury Control Branch injury database yielded 6 possible fall-related fatalities of young children in a population of 2.5 million young children over a 5-year period. The other databases and the literature review produced no data that would indicate a higher short-fall mortality rate. Most publications that discuss the risk of death resulting from short falls say that such deaths are rare. No deaths resulting from falls have been reliably reported from day care centers.

CONCLUSIONS

The best current estimate of the mortality rate for short falls affecting infants and young children is <0.48 deaths per 1 million young children per year. Additional research is suggested.

Injury biomechanics and child abuse

Child abuse is a leading cause of morbidity and mortality in young children and infants in the United States. Medical care providers, social services, and legal systems make critical decisions regarding injury and history plausibility daily. Injury plausibility judgments rely on evidence-based medicine, individualized experiences, and empirical data. A poor outcome may result if abuse is missed or an innocent family is accused, therefore evidence and science-based injury assessments are required. Although research in biomechanics has improved clinical understanding of injuries in children, much work is still required to develop a more scientific, rigorous approach to assessing injury causation. This article reviews key issues in child abuse and how injury biomechanics research may help improve accuracy in differentiating abuse from accidental events. Case-based biomechanical investigations, human surrogate, and computer modeling biomechanics research applied to child abuse injury are discussed. The goal of this paper is to provide an overview of key research studies rather than on review or commentary articles. Limitations and future research needs are also reviewed.

Injury risk of a 6-year-old wheelchair-seated occupant in a frontal motor vehicle impact--'ANSI/RESNA WC-19' sled testing analysis

Children with disabilities are transported on a daily basis to schools and developmental facilities. When they travel, they often remain seated in their wheelchairs in vehicles. To study injury risk of pediatric wheelchair users in motor vehicle crashes, three of the same pediatric manual wheelchairs were sled impact tested with a seated Hybrid III 6-year-old ATD using a 20 g/48 km/h frontal crash pulse. The sled test results were compared to kinematic limitations and injury criteria specified in the ANSI/RESNA WC-19, FMVSS 213 and FMVSS 208. All sled test results were below the limits specified in the ANSI/RESNA WC-19 standard and FMVSS 213. All tests exceeded the N(ij) limit of 1 specified in FMVSS 208, and one test exceeded the limit of peak neck tension force. Chest deflection resulting from one of three tests was at the limit specified in FMVSS 208. Our results suggest that children with disabilities who remain seated in their wheelchairs in vehicles may be at risk of neck injury in a frontal impact motor vehicle crash. However, limitations in the biofidelity of the Hybrid III ATD neck raise concern as to the translatability of these findings to the real world. Additional studies are needed to investigate the influence of neck properties and ATD neck biofidelity on injury risk of children who travel seated in their wheelchairs.

Influence of wet surfaces and fall height on pediatric injury risk in feet-first freefalls as predicted using a test dummy

INTRODUCTION

Falls are a major cause of morbidity and mortality in children, but are also reported falsely in child abuse. Therefore, it is of interest to understand those factors which may lead to a higher likelihood of injury in a feet-first freefall.

METHODS

We used laboratory freefall experiments and a 3-year-old Hybrid III anthropomorphic test dummy (ATD) to assess head and femur injury risk. Wet and dry linoleum impact surfaces were used from three fall heights: 22, 35 and 47 in.

RESULTS

For a given fall height, dry surfaces were associated with higher head injury criteria (HIC) values than wet surfaces. Changes in fall height 22-47 in. did not significantly affect HIC values for falls onto either surface. Generally, compressive and bending femur loading increased significantly for wet as compared to dry linoleum.

CONCLUSIONS

In simulated feet first freefall experiments up to 47 in. using a 3-year-old test dummy, a low risk of contact type head injury and femur fracture was found. However, both fall height and surface conditions influenced femur loading and head injury measures. Future efforts should explore the risk of head injury associated with angular acceleration in freefalls.

The effects of wheelchair-seating stiffness and energy absorption on occupant frontal impact kinematics and submarining risk using computer simulation

Many wheelchair users must travel in motor vehicles while seated in their wheelchairs. The safety features of seat assemblies are key to motor vehicle occupant crash protection. Seating system properties such as strength, stiffness, and energy absorbance have been shown to have significant influence on risk of submarining. This study investigated the effects of wheelchair seat stiffness and energy absorption properties on occupant risk of submarining during a frontal motor vehicle 20 g/30 mph impact using a validated computer crash simulation model. The results indicate that wheelchair-seating stiffness and energy absorption characteristics influence occupant kinematics associated with the risk of submarining. Softer seat surfaces and relatively high energy absorption/permanent deformation were found to produce pelvis excursion trajectories associated with increased submarining risk. Findings also suggest that the current American National Standards Institute/Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/RESNA) WC-19 seating integrity may not adequately assess submarining risk.

Evaluation of wheelchair sling seat and sling back crashworthiness

Many wheelchairs are used as vehicle seats by those who cannot transfer to a vehicle seat. Although ANSI/RESNA WC-19 has been recently adopted as a standard to evaluate crashworthiness of the wheelchairs used as motor vehicle seats, replacement or after-market seats may not be tested to this standard. This study evaluated the crashworthiness of two specimens each of three unique sling backs and three unique sling seats using a static test procedure intended to simulate crash loading conditions. To pass the test, a sling back is required to withstand a 2290 lb load, and a sling seat should be capable of withstanding a 3750 lb load. All, but two sling back specimens which failed at 1567 lb and 1787 lb, withstood the test criterion load. Two of six tested sling seats failed to pass the test: one failed at 3123 lb and the other failed to sustain the load for 5 s although it reached the test criterion load. Most of the failures occurred at the seams of the side openings of upholsteries where the wheelchair frame inserts for attachment.

Experience with wood lamp illumination and digital photography in the documentation of bruises on human skin

Bruising is very common in children. Examination of bruising can guide the clinician in ordering radiographic imaging studies of children who have suffered trauma. Additionally, bruising in infants and patterns of bruising that do not match the injury scenario offered by caretakers can raise the suspicion of abuse. This article reports preliminary experience with Wood lamp enhancement of faint bruises and visualization of bruises that are not visible. It describes the method for digital photography of bruises visualized in this way. Finally, it suggests future applications and areas of further study.

Wheelchairs used as motor vehicle seats: seat loading in frontal impact sled testing

Wheelchairs are not typically designed to function as motor vehicle seats. However, many wheelchair users are unable to transfer to a vehicle seat and instead travel seated in their wheelchair. ANSI/RESNA WC19: Wheelchairs Used as Seats in Motor Vehicles provides design and testing requirements, but does not provide wheelchair manufacturers with design guidance related to expected loads imposed upon wheelchair components during a crash. To provide manufacturers with crashworthy design guidance, our study measured wheelchair seat loading during 20g/48kph frontal impact sled tests with a 50th percentile male test dummy. Loading conditions were assessed using two different rear securement point positions. Results of four sled impact tests revealed downward loads ranging from 17 019 to 18 682 N, depending upon rear securement point configuration. Maximum fore/aft shear loads ranged from 4424 to 6717 N across the tests.

Evaluation of wheelchair drop seat crashworthiness

Wheelchair seating crash performance is critical to protecting wheelchair users who remain seated in their wheelchairs during transportation. Relying upon computer simulation and sled testing seat loads associated with a 20 g/48 kph (20 g/30 mph) frontal impact and 50th percentile male occupant were estimated to develop test criteria. Using a static test setup we evaluated the performance of various types of commercially available drop seats against the loading test criteria. Five different types of drop seats (two specimens each) constructed of various materials (i.e. plastics, plywood, metal) were evaluated. Two types of drop seats (three of the total 10 specimens) met the 16650 N (3750 lb) frontal impact test criteria. While additional validation of the test protocol is necessary, this study suggests that some drop seat designs may be incapable of withstanding crash level loads.

Evaluation of wheelchair seating system crashworthiness: "drop hook"-type seat attachment hardware

OBJECTIVE

To evaluate the crashworthiness of commercially available hardware that attaches seat surfaces to the wheelchair frame.

DESIGN

A low cost static crashworthiness test procedure that simulates a frontal impact motor vehicle crash.

SETTING

Safety testing laboratory.

SPECIMENS

Eleven unique sets of drop-hook hardware made of carbon steel (4), stainless steel (4), and aluminum (3).

INTERVENTIONS

Replicated seat-loading conditions associated with a 20g/48 kph frontal impact. Test criterion for seat loading was 16,680 N (3750 lb).

MAIN OUTCOME MEASURES

Failure load and deflection of seat surface.

RESULTS

None of the hardware sets tested met the crashworthiness test criterion. All failed at less than 50% of the load that seating hardware could be exposed to in a 20g/48 kph frontal impact. The primary failure mode was excessive deformation, leading to an unstable seat support surface.

CONCLUSIONS

Results suggest that commercially available seating drop hooks may be unable to withstand loading associated with a frontal crash and may not be the best option for use with transport wheelchairs.

Evaluation of wheelchair back support crashworthiness: combination wheelchair back support surfaces and attachment hardware

Automotive seats are tested for compliance with federal motor vehicle safety standards (FMVSS) to assure safety during impact. Many wheelchair users rely upon their wheelchairs to serve as vehicle seats. However, the crashworthiness of these wheelchairs during impact is often unknown. This study evaluated the crashworthiness of five combinations of wheelchair back support surfaces and attachment hardware using a static test procedure simulating crash loading conditions. The crashworthiness was tested by applying a simulated rearward load to each seat-back system. The magnitude of the applied load was established through computer simulation and biodynamic calculations. None of the five tested wheelchair back supports withstood the simulated crash loads. All failures were associated with attachment hardware.

Proposed test method for and evaluation of wheelchair seating system (WCSS) crashworthiness

Safety of motor vehicle seats is of great importance in providing crash protection to the occupant. An increasing number of wheelchair users use their wheelchairs as motor vehicle seats when traveling. A voluntary standard requires that compliant wheelchairs be dynamically sled impact tested. However, testing to evaluate the crashworthiness of add-on wheelchair seating systems (WCSS) independent of their wheelchair frame is not addressed by this standard. To address this need, this study developed a method to evaluate the crash-worthiness of WCSS with independent frames. Federal Motor Vehicle Safety Standards (FMVSS) 207 test protocols, used to test the strength of motor vehicle seats, were modified and used to test the strength of three WCSS. Forward and rearward loads were applied at the WCSS center of gravity (CGSS), and a moment was applied at the uppermost point of the seat back. Each of the three tested WCSS met the strength requirements of FMVSS 207. Wheelchair seat-back stiffness was also investigated and compared to motor vehicle seat-back stiffness.

Wheeled mobility device database for transportation safety research and standards

To address the issue of safely accessing and securing wheeled mobility devices in motor vehicles, more information characterizing current-production devices was needed. In a recent effort, frame characteristics of wheeled mobility devices were defined and a database developed for recording characteristics relevant to access and securement. A representative number of devices have been surveyed to measure key characteristics, and these measures have been recorded in the database. This paper details the development of the database and frame characterization scheme, the methods used to survey currently available wheeled mobility devices, and some descriptive statistics resulting from an analysis of the data. A discussion of how this information is being used in research aimed at developing technology and safety standards to ensure vehicle access and safe transportation, as well as other potential uses, is also included.