Much of the improvement in motor-vehicle safety for drivers and passengers over the past thirty to forty years has been achieved through improved vehicle crashworthiness and restraint-system technologies that are, in large part, due to improvements in safety regulations and restraint system performance requirements set forth by the NHTSA in federal motor vehicle safety standards (FMVSS). In addition, significant contributions to reductions in occupant injury risks have also been achieved through the implementation of seatbelt laws by states and by federal education campaigns, such as “Click-It-or-Ticket,” that have resulted in significant increases in seatbelt use by adults and in the use of safety seats and booster seats by children. However, during the same time that injury risks for people using vehicle manufacturer’ seats and occupant-protection systems have been dramatically reduced, increasing numbers of people with physical and/or cognitive disabilities have been traveling in motor vehicles while seated in wheelchairs, and available evidence suggests that these travelers are at significant greater risk of serious-to-fatal injuries in crash and even non-crash events. For this population of vehicle occupants, safe transportation and effective occupant crash protection depends on the ability to use and effectively secure crashworthy wheelchairs, and the ability to properly use complete belt-restraint systems consisting of both upper and lower torso belts, all or part of which are aftermarket products installed by vehicle modifiers. Upon recognizing the transportation safety problem for travelers seated in wheelchairs and the fact that federal motor vehicle safety standards generally do not apply to the aftermarket restraint systems required by most occupants seated in wheelchairs, or to wheelchairs and wheelchair securement systems, national and international industry standards have been developed for these products relative to their use in motor vehicles. While these voluntary industry standards are critical to improving transportation safety for travelers seated in wheelchairs, it is equally important to make sure that vehicle modifiers and other key stakeholders are aware of these standards so that compliant products are made available and used. It is also important that all parties involved in the transportation of occupants seated in wheelchairs (i.e., in wheelchair transportation safety, or WTS) are knowledgeable about “best practice” in transporting people in wheelchairs safely. In this project, work was conducted on five Subtasks with the goal of improving transportation safety for occupants of motor vehicles seated in wheelchairs. While the project addressed transportation safety for both passengers and drivers seated in wheelchairs, a primary focus of the project was on drivers who operate personal vehicles (primarily vans and minivans) while seated in their wheelchair. In Subtask 1, results of investigations and analyses of crash and non-crash events involving one or more occupants seated in wheelchairs indicate that a primary reason for these occupants sustaining serious-to-fatal injuries, even in minor to moderate crashes and non-crash events such as sudden braking, is a lack of use and/or proper positioning of a crashworthy lap/shoulder-belt restraint system. Although statistical analyses of injury factors for people seated in wheelchairs during frontal crashes in the UMTRI wheelchair-occupant crash injury database are currently limited by the relatively small sample size (n = 74 wheelchair occupants), the results suggest that current belt restraints are not as effective in preventing serious-to-fatal injuries for this population of travelers as they are for people seated in vehicle seats. This may be because drivers and passengers seated in wheelchairs have lower injury tolerance than the average vehicle occupant using vehicle seats. However, it is also known that vehicle occupants who remain seated in their wheelchairs when traveling in motor vehicles often have difficulty achieving proper or optimal positioning of lap/shoulder belt restraints due to interference by wheelchair arm supports with proper positioning of vehicle-anchored lap belts by wheelchair components, and especially interference of lap-belt positioning in contact with the lower pelvis. In addition, positioning of occupants in wheelchairs further from the side of the vehicle compared to outboard occupants using vehicle seats often causes the shoulder belt to be position off the side of the shoulder rather than near the center of the shoulder, thereby reducing the effectiveness of shoulder belts in reducing chest and head excursions in frontal crashes. A study of twenty-one people who drive a personal vehicle while seated in their wheelchairs confirmed that these drivers are often using poorly positioned and/or incomplete lap/shoulder belt restraints that would offer relatively little protection in frontal crashes, and would be more likely to cause abdominal and chest injuries than a properly positioned lap/shoulder belt. In many cases, this is because the driver requires a pre-buckled (i.e., passive) lap/shoulder belt due to the lack of manual dexterity required to buckle and unbuckle a standard seat belt, combined with a wheelchair having closed-front arm supports that prevent the proper placement of a passive lap belt low on the pelvis and in contact with the body when the driver moves forward into the driving position. In Subtask 2, an effort to improve seat-belt restraint systems for frontal crash protection of drivers seated in wheelchairs evaluated several design approaches and prototype systems. The most promising system is referred to as the seat-belt deployment system, or SBDS. This design provides add-on vehicle components that allow drivers seated in wheelchairs to use the vehicle manufacturer’s (OEM) lap/shoulder belt restraint in a nearly passive mode (pre-buckled seat belt activated by an accessible button), while eliminating obstacles on the vehicle floor that can interfere with maneuvering a wheelchair into the driver space. A prototype SBDS has been successfully evaluated in a static minivan laboratory buck and in several 48-kph, 20-g frontal impact sled tests. Efforts to improve rear-impact protection for drivers seated in wheelchairs include the development and successful sled-impact testing of a deployable head-and-back restraint system developed by a Biomedical Engineering (BME) senior design team under the supervision of UMTRI faculty and staff. However, the primary focus was on the evaluation and improvement of a commercially available vehicle-anchored head-and-back restraint system that the driver deploys behind his/her wheelchair or moves into the stored position against the side of the vehicle by means of an accessible button. Several changes to the design and performance of the head-and-back restraint system received from the inventor were made by UMTRI based on sledtest results, and have been conveyed to the manufacturer so that improvements to the commercially available equipment can also be made. The goal of Subtask 3 was to determine the potential benefits of steering-wheel air bags for drivers seated in wheelchairs versus the risks of being seriously injured by deploying air bags. Forty-eight kph frontal sled tests and MADYMO computer simulations of small-female and midsize-male drivers (i.e., crash-test dummies) seated in wheelchairs in the driver space were conducted with and without deployment of an advanced steering-wheel airbag. All sled tests and simulations used a range of seat-belt configurations, including good and poor (loose) seat-belt positioning, as well as no belt restraint. The computer models were validated using results from frontal sled-impact tests with steering-wheel air bag deployments, and the validated models were used in simulation matrices to investigate the protective benefits and injury risks associated with allowing steering-wheel airbags to deploy or deactivating the steering-wheelchair airbag in 48- kph frontal crashes. Simulation matrices included angled frontal crashes at 15- and 30-degrees to 12 o’clock, midsize-male and small-female drivers in wheelchairs positioned in close proximity (125 mm and 25 mm) to the air-bag module at the onset of frontal-crash deceleration, and small-female drivers seated in a surrogate wheelchair versus a minivan driver seat. The results of these tests and simulations show little basis for concern that the energy of deploying “advanced” steering-wheel air bags in today’s vehicles will cause serious-to-fatal injuries to drivers seated in wheelchairs. Rather, the steering-wheel air bag almost always reduces the risk of head, neck, and chest injuries due to contact with the steering wheel that can occur when the air bag is deactivated. Also, in angled frontal impact, deployment of the side curtain airbag offers additional protection to drivers in wheelchairs. The results of this study therefore indicate that steering-wheel air bags will generally offer tangible safety and crash protection benefits for a wide range of drivers seated in wheelchairs just as they do for drivers in vehicles seats, and should only be deactivated on rare occasions. The only situation when consideration should be given to deactivating a steering-wheel air bag for a driver seated in a wheelchair is when the driver is positioned with their chest or chin located 8 inches or less from the air-bag module during normal operation of the vehicle, which is the same as the recommendation for when to deactivate airbags for short drivers in vehicle seats. In this regard, using a lap/shoulder belt with a fixed B-pillar anchor point rather than a retractor-based anchorage may offer several potential benefits to drivers seated in wheelchairs. In addition to providing for greater torso stability in the driver’s optimal posture for operating the vehicle, and removing seat-belt retractor forces that can pull drivers away from their preferred driving posture, a properly adjusted seat belt with a fixed shoulder-belt anchor point would prevent the wheelchair driver’s head and torso from moving closer to the airbag module during pre-impact braking and prior to airbag deployment during a frontal crash. Implementing fixed shoulder-belt anchor points on B-pillars should, however, be done in a manner that does not compromise seat-belt load limiters and/or seat-belt pre-tensioners. If efforts toward improving transportation safety for occupants seated in wheelchairs such as those performed in this study and through development of voluntary wheelchair transportation safety standards, are to have to have a meaningful impact in the real world, there is a need to inform and educate key stakeholders regarding the existence of products that comply with voluntary industry standards and of best practice in providing safe transportation to travelers seated in wheelchairs. Toward this end, “Safety Tip Sheets” targeted to vehicle modifiers and other key stakeholder groups have been developed in Subtask 4, and a DriveSafe brochure is nearly ready for printing and distribution. The latter provides key steps to safe transportation and optimal crash protection for drivers who remain seated in wheelchairs, and is similar to the widely distributed and successful RideSafe brochure that is targeted primarily for passengers seated in wheelchairs. In Subtask 5, a new Wheelchair Transportation Safety (WTS) website was developed that provides a wide range of educational materials for vehicle modifiers and other key WTS stakeholders. The website includes articles on WTS written for various consumer magazines over the past decade, downloadable sled-test videos that show the potential negative consequences of several wheelchair-tiedown and occupant-restraint misuse scenarios, answers to many frequently asked questions regarding wheelchair transportation safety, and summaries of the latest WTS standards for wheelchairs, WTORS, and wheelchair seating systems. The website provides access to the RideSafe brochure and will soon include access to the DriveSafe brochure as well as to several sets of Safety Tip Sheets for different stakeholder groups. An important aspect of the website is frequently updated lists of products that comply with WTS standards so that clinicians and consumers can find compliant products in one location. While significant progress has been made during this project toward improving transportation safety and crash protection for occupants seated in wheelchairs, and particularly for drivers of personal vehicles who remain seated in their wheelchairs, there is a need for additional work. To a large extent, this involves implementing the results of the work completed to date, such as commercialization of the seat-belt deployment device. There is also a critical need to continue efforts to educate vehicle modifiers, their clients, and other key stakeholder groups with regard to implementing best practice in wheelchair transportation safety, and to prescribing and using products that have been tested to, and that fully comply with, WTS standards. It would also be beneficial to continue to investigate, analyze, and document, crash and non-crash events involving drivers and passengers seated in wheelchairs to increase the sample size of cases available for statistical analyses to clarify the reasons why “optimal” restraint use and occupant age were not found to be significant predictors of injury for occupants in wheelchairs and to determine comparative injury risk and risk factors for occupants in wheelchairs who are involved in side impacts, rear impacts, and rollover crashes. Finally, there are many questions that continue to be posed by professionals who work with wheelchair users and who train people with disabilities to drive for which there are currently no clear evidence-based answers. To answer these questions, additional research and testing are required. (Author/publisher)
Abstract