Wheelchair Occupant Research Articles

Development and validation of rear impact computer simulation model of an adult manual transit wheelchair with a seated occupant

It has been shown that ANSI WC19 transit wheelchairs that are crashworthy in frontal impact exhibit catastrophic failures in rear impact and may not be able to provide stable seating support and thus occupant protection for the wheelchair occupant. Thus far only limited sled test and computer simulation data have been available to study rear impact wheelchair safety. Computer modeling can be used as an economic and comprehensive tool to gain critical knowledge regarding wheelchair integrity and occupant safety. This study describes the development and validation of a computer model simulating an adult wheelchair-seated occupant subjected to a rear impact event. The model was developed in MADYMO™ and validated rigorously using the results of three similar sled tests conducted to specifications provided in the draft ISO/TC 173 standard. Outcomes from the model can provide critical wheelchair loading information to wheelchair and tiedown manufacturers, resulting in safer wheelchair designs for rear impact conditions.

Use of power tilt systems in everyday life

Purpose. The goal of this study was to monitor and describe the use of power tilt systems in everyday life. Additionally, tilt measurements were used to determine if participants performed regular pressure reliefs.Methods. Wheelchair occupancy and seat position of 16 fulltime power wheelchair users were monitored regularly for 1–2 weeks. Daily wheelchair occupancy, typical position, time spent at different tilt angles, tilt frequency and pressure relieving tilt (PRT) frequency were described.Results. Participants used their tilt systems in many different ways, including subjects who typically sat at small (0–14°) tilt angles and subjects who typically sat at medium (15–29°) tilt angles. Few subjects tilted past 45°. Almost all subjects tilted throughout the day, with the median subject performing >3 tilts per hour of wheelchair occupancy. Despite the regular use, few subjects performed regular PRTs (median = 0.13/h)Conclusion. Differences in tilt-use illustrated the variability in function and activity among users, as well as the diverse benefits of a tilt system for different users. Further study into why subjects did not regularly achieve PRT magnitudes would be valuable to inform improved training, education and follow-up.

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.

Safety review of wheelchair users in road passenger vehicles

Over the last 20 years in France as well generally in Europe and also in North America the integration of disabled people into society has become a more and more pressing issue. This French research project RETENUE aims at increasing the safety level of wheelchair occupants up to becoming equivalent to that of able-bodied road vehicle occupants. Current world practices are that wheelchair occupants who are unable to transfer to a vehicle seat for transportation remain in their wheelchair which is secured to the vehicle floor using tie downs, and the occupant is restrained in the wheelchair. The main phases in the project are: bibliography, materials, sled tests and methods. The paper reviews existing devices, methods and current legislation and proposes sled tests matrices and preliminary results to analyse the crashworthiness of these devices.

Safety assessment of wheelchair occupants in paratransit buses

Safety assessment of passengers with disabilities travelling in their wheelchairs in paratransit buses is presented. Computational mechanics and LS-DYNA non-linear finite element code were used as tools in this study. All finite element models were partially validated using data available from experimental sled tests. The validated dummy-wheelchair-bus system, which was developed, allowed for quantitative assessment of injury criteria in several accident scenarios. Although backward seating was found beneficial in reducing severity of injuries during accidents, the outcome is sensitive to imperfect initial conditions during accidents. Material presented allows for detailed assessment of benefits and shortcomings of each configuration considered.

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.

The Safety Assessment of Wheelchair Occupants in Road Passenger Vehicles in a Frontal Crash: A Computer Simulation

With the increasing needs of the more convenient transportation, wheelchairs are often used by people with mobility disabilities and the elderly people. However, as wheelchairs are primarily designed for the mobility assistive devices, not for the vehicle seats, wheelchair users are exposed to risk factors for neck and upper body injury caused by automobile accidents. In this paper, in accordance with the ANSI/RESNA WC-19, a fixed vehicle mounted wheelchair occupant restraint system (FWORS), wheelchair integrated restraint system (WIRS), and wheelchair integrated x-bend restraint system (WIXRS) are evaluated using computer simulations for the case when a wheelchair is subjected to the frontal impact (20 g, 48 km/h).

Concept of a platform-based impact isolation system for protection of wheelchair occupants from injuries in vehicle crashes

To improve the protection of a wheelchair-seated person with disabilities traveling in a vehicle from injuries in a crash, it is proposed to attach the wheelchair to a movable platform separated from the vehicle body by means of a shock isolator. The control of the platform is designed to reduce the occupant's injury risk, as compared with the case of the attachment of the wheelchair directly to the vehicle. The isolator design is based on the minimization of the force transmitted to the wheelchair occupant, provided that the space allowed for the platform to move relative to the vehicle is constrained. The possibility of pre-acting control, when the isolator is engaged for a time prior to the crash, is discussed. Passive tiedown and restraint systems are studied, although it is recognized that active systems could provide even lower injury risks. A multibody model of the platform-based occupied wheelchair is utilized for full-scale simulation of the response of the system to a crash pulse. The simulation shows a noticeable reduction in the injury risk due to the platform and an even greater reduction of injury with pre-acting control.

Experimental evaluation of the wheelchair occupant protection under different impact conditions using commercial wheelchairs

Mobility is a necessity for the population and to guarantee the access to the transport for all people with a minimum safety level must be an objective for our society. When wheelchair users access a vehicle and are unable to transfer to a seat, even when they are helped by other people, the wheelchair itself turns into a vehicle seat. The problem arises in the event of an impact, because wheelchairs are designed as mobility technical aidswith low weight as amain objective, butmost of themwithout specific safety requirements that allow wheelchairs to withstand the loads generated during an impact and to protect the wheelchair occupant. This work evaluates different commercial wheelchairs regarding its behaviour under three impact conditions (front, rear, and side) using different wheelchair tie-down and occupant-restraint systems (WTORS). In these conditions, the aspects that have more influence on the wheelchair occupant safety during an impact in a motor vehicle are analysed. Impact tests, mainly in rear and side directions, showed a very low level of occupant protection, due to the insufficient wheelchair structure strength and, in some cases, due to the inefficiency of a type of WTORS. In frontal impacts, submarining and dummy neck loads are the most critical parameters to achieve a good level of protection. The low strength of the wheelchair backrest is the main factor that increases the occupant injury risk in rear impacts, while the collapse of the wheelchair structure occurred in side impacts.

Evaluation of wheelchair occupant safety in frontal & side impact of wheelchair loaded vehicle by Computer Simulation Analysis Method (Adams+Lifemod)

Evaluation of wheelchair occupant safety in frontal & side impact of wheelchair loaded vehicle by Computer Simulation Analysis Method (Adams+Lifemod)

Development of models of scoliosis for crash safety analysis of wheelchair occupants

Development of models of scoliosis for crash safety analysis of wheelchair occupants

시뮬레이션 기법을 이용한 차량내 전동휠체어 탑승자의 전방 충돌시 안전에 관한 연구

With increasing need of transportation services for people with disabilities and the aged, wheelchairs are used as their assistive devices to participate in daily and recreational activities and as seats of motor vehicle. However, as wheelchairs are primarily designed for mobility assistive devices, not for vehicle seats, wheelchair users may experience serious injury when they meet car crashes. To date, neither engineering guidance for a wheelchair mounting system on the vehicle floor nor safety assessment analysis by a car crash has been studied for the domestic users. In this paper, in accordance with the ANSI/RESNA WC-19, a fixed vehicle mounted wheelchair occupant restraint system (FWORS), wheelchair integrated restraint system (WIRS), and wheelchair integrated x-bend restraint system (WIXRS) subjected to frontal impact (20 g, 48 ㎞/h) were analyzed using computer simulations for domestic users. We present surrogate wheelchair occupant safety by head injury criteria (HIC), motion criteria (MC), and combined injury criteria (CIC).

Pilot Study of Safety Belt Usability for Vehicle Occupants Seated in Wheelchairs

This study investigates the usability of wheelchair occupant restraint systems (WORS) that are used for crash protection of individuals seated in wheelchairs during motor vehicle transit. Ten independent adults with significant functional limitations who use wheelchairs for primary mobility were observed and interviewed while performing reach and manipulation tasks associated with WORS usage. Participants' opinions on ease of use and comfort-related factors were obtained for four occupant restraint scenarios. The study results show evidence of user problems with common WORS designs for use by wheelchair-seated individuals with significant functional limitations. Results from this pilot study suggest redesign of latch plates and buckles used in WORS to enable wheelchair-seated individuals with functional limitations to don and buckle belt restraints more easily and independently. Additionally, this study provides guidance to occupant-restraint manufacturers and wheelchair designers regarding belt-restraint usability. Improved WORS usability will complement other efforts to increase frequency of safety belt usage and lead to improved occupant safety.

Wheelchair integrated occupant restraints: feasibility in frontal impact

Individuals often use their wheelchair as a motor vehicle seat when traveling in motor vehicles. The current use of fixed vehicle-mounted wheelchair occupant restraint systems (FWORSs) often results in poor belt fit and discomfort. Additionally, satisfaction, usability and usage rate of FWORSs during transit use are often low. The automotive industry has shown improved occupant restraint usage, belt fit and injury protection when integrating the upper torso and pelvic restraint in a motor vehicle seat. This study compared occupant injury measures of a FWORS to a concept wheelchair integrated restraint system (WIRS) using a 20 g frontal sled impact test with a 30 mph change in velocity. Neck loads, neck moments, head, pelvis and chest acceleration, sternum compression and knee and head excursion data were recorded from the wheelchair seated 50th percentile male hybrid III anthropomorphic test dummy (ATD). The WIRS resulted in a lower head injury criteria (HIC) value, lower sternum compression and a lower upper-torso restraint load than the FWORS. Compared with the FWORS, increased head, knee and wheelchair excursions and higher neck loads and moments were measured in the WIRS test. Both restraint scenario injury parameters were complied with occupant injury criteria based on General Motors Injury Assessment Reference Values (GM-IARVs) and occupant kinematic requirements defined by the Society of Automotive Engineers (SAE) voluntary standard, J2249. A higher motion criteria index was calculated for the WIRS scenario and a comparable combined injury criteria index was calculated for both restraint scenarios. The sled impact test showed WIRS concept feasibility, facilitating further development by industrial manufacturers who might further want to pursue this restraint principle to increase wheelchair occupant safety and comfort during transport in motor vehicles.

Development of a wheelchair occupant injury risk assessment method and its application in the investigation of wheelchair securement point influence on frontal crash safety

To promote proper wheelchair securement in transportation, the proposed ANSI/RESNA Standard on Wheelchairs Used as Seats in Motor Vehicles will require that all transit wheelchairs be equipped with four securement points compatible with strap-type tiedowns. Through computer simulations, the location of these securement points has been found to influence wheelchair user response to a frontal crash. This study develops and employs an injury risk assessment method to compare the crashworthiness of various securement point configurations. The comparative injury risk assessment method is designed to predict the risk associated with internalized crash forces, as well as risk associated with secondary occupant impact with the vehicle interior. Injury criteria established by Federal Motor Vehicle Safety Standards and General Motors, along with excursion limitations set by the Society of Automotive Engineers (SAE) J2249 Wheelchair Tiedowns and Occupant Restraint Systems (WTORS) Standard were used as benchmarks for the risk assessment method. The simulation model subjected a secured commercial powerbase wheelchair with a seated 50th percentile male Hybrid III test dummy to a 20 g/30 mph crash. The occupant was restrained using pelvic and shoulder belts, and the wheelchair was secured with four strap-type tiedowns. Results indicated that securement points located 1.5 in to 2.5 in above the evaluated wheelchair's center of gravity provide the most effective occupant protection.

Physical Properties of a New Orthopaedic Supporting Material for Posture Control in Wheelchairs

Providing a support surface with an even pressure distribution for wheelchair occupants is one of the primary objectives in clinical practice. Consequently a new warp-knit fabric has been developed with the aim to provide a more ideal orthopaedic support. The fabric, which has been described in a US patent, comprises a lock-knit stitch with a laid-in yarn and is made by using three guide bars with nylon and elastic yarns. In a clinical trial it was observed that users found this new fabric system to be more comfortable than a conventional wheelchair material. The relationship between relevant fabric properties (including the supporting characteristics of the fabric) and the findings of the clinical trial were investigated. Comparisons of interface pressure were made on 5 nondisabled subjects sitting on a hard surface, a conventional wheelchair seat and the new fabric under different pre-stressed tension loading. Preliminary results indicated that the average pressure under the ischial tuberosities was red...

Wheelchair-related accidents

This study set out to determine the prevalence of wheelchair-related accidents, the circumstances in which they occur, the nature of injuries sustained, and to identify types of accident which are potentially avoidable. A postal questionnaire was sent to a random sample of 250 of the 4334 wheelchair users in the Leeds Eastern Health District. Those reporting accidents to themselves or their attendant were then interviewed by telephone. Of the 174 wheelchair users who completed the postal questionnaire, 48 reported accidents to themselves or others. Of wheelchair occupants 18% had had wheelchair-related accidents, falls being the most frequently reported with five users sustaining a fracture. Accidents involving wheelchair attendants were reported by 15.5% of users. It is concluded that wheelchair-related accidents are not uncommon and whilst most are minor, serious injuries can result. There is scope for prevention of many of these accidents for both wheelchair users and attendants.

Wheelchair occupant restraints in motor vehicles

The issue of safety for wheelchair users in motor vehicles has been raised in Australia by parents of young people with disabilities. Investigations revealed that wheelchair users were not covered by any legislated safety requirements, and each case received special dispensation from compliance with regulations covering the able-bodies population. Dynamic testing of restraint systems at the University of Michigan had revealed that existing systems were unsafe. Dynamic tests confirmed those findings on systems used at that time in Australia. Testing led to the design, development and marketing of a new wheelchair occupant and restraint system which remains a system of choice for use by organisations where the same people use the same buses in the same position each day. Australian Standard 2942-1987, Wheelchair Occupant Restraint Assemblies for Use in Motor Vehicles, has since been developed. It establishes design and performance requirements for these restraints and includes details of dynamic testing procedures. This paper describes the development of the above restraint system and the subsequent Australian Standard.