Wheelchair Transportation Safety
Frequently Asked Questions
The answers to FAQs provided in this document are intended for people who use wheelchairs, parents, practitioners, clinicians and medical personnel, physical and occupational therapists, transit providers, school-bus transportation companies and personnel, transportation systems administrators, and the manufacturers of wheelchairs, wheelchair seating systems, and after-market wheelchair tiedown and occupant restraint systems who are concerned with transportation safety for children and adults who remain seated in their wheelchair when traveling in a motor vehicle. These answers have been developed in response to questions arising from the voluntary standards for designing and testing:
- devices used for wheelchair securement (tiedown) and belt-type occupant restraints,
- wheelchairs intended for use as seats in motor vehicles, and
- wheelchair seating systems intended for occupancy in motor vehicles.
Some questions and answers apply to transportation safety in general. Others are related to specific issues that have been raised or for which there has been misunderstanding about what the standards say or mean.
The questions and answers have been arranged into the following four groups:
A. General (Transport safety principles and issues)
B. Wheelchair Tiedown and Occupant Restraint Systems (RESNA WC18 and ISO 10542-1 standards)
C. Transport Wheelchairs (RESNA WC19 and ISO 7176-19 standards)
D. Wheelchair Seating (RESNA WC20 and ISO-16840-4 standards)
Acronyms and Abbreviations: Use this resource to translate the terms and acronyms used throughout documents related to wheelchair and occupant transportation safety.
Note: If you do not find an answer to your question below, please send your question to:
- Larry Schneider at firstname.lastname@example.org
- Miriam Manary at email@example.com
We will do our best to respond. If appropriate, your question and our response will be added to this FAQ forum without identifying you.
Group A Questions: General
(click on the question and it will take you to the answer)
A-1: What are the main safety concerns and issues for someone seated in a wheelchair while in a motor vehicle?
First, let's think about some of the primary occupant-protection features that are used in family vehicles, i.e. cars, vans and SUVs. The seats are firmly anchored to the vehicle floor, and they are designed without rigid sharp edges that could cause injury. The seats are also designed and dynamically tested to ensure that they will provide effective support for the occupant. A properly designed three-point belt restraint will provide effective upper and lower torso restraint by applying forces to the skeletal structures of the body. The vehicle seat and belt restraint system work together to prevent occupant ejection and minimize the potential for occupant contact with the vehicle interior, which causes injury.
Since the early 1990s, all passenger vehicles have been equipped with airbag restraints that deploy rapidly in frontal crashes to provide additional protection to the heads, faces, necks, and chests of front-seat occupants. In this way, the seat and occupant restraints (belts plus airbags) work with the vehicle structure's ability to withstand a crash, to form a safety system that allows the occupant to “ride-down” or gradually absorb the vehicle deceleration. This would reduce contact with vehicle interior structures, thereby minimizing the possibility of serious injury.
In contrast to the seats come standard as a part of the vehicle, most wheelchairs have not been designed for use as seats in motor vehicles. The wheelchair frames and seats are generally not strong enough to withstand the thousands of pounds of impact forces that can result under crash conditions. For many wheelchairs, it is difficult to find suitable places on the wheelchair frame for attaching wheelchair tiedowns. Even when it is possible to find usable attachment points, it is unlikely that those places are strong enough to hold up under a significant crash. In many cases, tiedown straps are attached to the most accessible places on the wheelchair, which are often the weakest places. For example, if tiedown straps are attached to footrests or armrests that are detachable, the wheelchair will not withstand even a relatively minor crash event. If the wheelchair is not effectively secured, the mass of the wheelchair, which can exceed 250 lb, will add to the belt-restraint forces on the occupant’s body in a crash situation.
In addition, for effective occupant protection, belt restraints must fit over the pelvis and shoulders. However, the design of most wheelchairs makes positioning of vehicle-anchored restraints difficult and often prevents a good fit of the occupant restraint due to the location of arm rests, push wheels and seat frame panels.
Injury biomechanics research and crash investigation data show that the orientation of the occupant in the vehicle relative to the impact direction also has significant safety implications. In many cases, wheelchair occupants are placed facing sideways in the vehicle, since this is easiest for getting wheelchair occupants in and out of the vehicle. When facing sideways, the occupants are in the least-safe orientation for enduring a frontal crash, which is the direction of impact that accounts for in excess of 50% of injury accidents. While occupants who face rearward can be provided with effective frontal impact protection if they are backed closed up to a high-backed padded structure, this is difficult to achieve in practice and is often not acceptable in many transportation situations. In the absence of properly designed back and head support structures, all occupied wheelchairs should be oriented facing forward during transit in a vehicle.
Trays and tray-mounted accessories, such as laptop computers or communication devices, are rarely fixed to wheelchairs in a manner necessary to minimize the chance of injury. It is therefore recommended that these devices be stowed elsewhere during transit. If they must remain on the wheelchair, they should be attached with stronger mechanisms or tethers to prevent them from breaking loose in a crash.
Clearly, the years of automotive crash safety research that has made our motor vehicles safer over time is only now being extended to people who use motor vehicle transportation while seated in their wheelchairs. In most cases, transfer to the vehicle seat will offer the highest level of occupant protection since the occupant can then use seats and restraint systems that comply with federal motor vehicle safety standards, and other consumer-rating tests. Those wheelchair users who remain seated in their wheelchairs while traveling in motor vehicles will be at increased risk of injury in a collision for the reasons outlined above, unless some additional steps are taken to implement the proven safety features.
For more information on the biomechanics of injury prevention and wheelchair transport safety see:
- WTORS-RP-J2249-Application Guidelines (June, 1999)
A-2: What steps are being taken to improve injury prevention for wheelchair-seated vehicle users?
Because the federal safety standards administered by the National Highway Traffic Safety Administration (NHTSA) generally only apply to the original vehicle manufacturer, after-market vehicle add-on equipment used in the transportation of wheelchair-seated drivers is not regulated by these standards. Until recently, this equipment had not been designed to hold up under the forces that are typically generated by the wheelchair and occupant in crash situations, and hadn't been designed with basic principles of occupant protection in mind. As indicated in the answer to Question A-1, the level of occupant safety and protection available to wheelchair-seated occupants has been far below that available to able-bodied travelers. Able-bodied travelers use seating and restraint systems that are regulated by federal motor vehicle safety standards and numerous consumer ratings tests.
In recognition of this problem and the fact that government standards were not going to be developed for these after-market vehicle products in the foreseeable future, the Restraints Task Force was formed within the Society of Automotive Engineers (SAE’s) Adaptive Devices Subcommittee. The purpose of the task force was to establish a Recommended Practice (RP) of design and performance requirements for wheelchair tiedown and occupant restraint systems (WTORS) that are used by wheelchair-seated occupants. SAE RP J2249 Wheelchair Tiedowns and Occupant Restraint Systems for Use in Motor Vehicles was completed and published in 1996. Today there are many WTORS on the market that comply with the requirements of this RP.
As the SAE Restraints Task Group was nearing completion of SAE J2249, and as WTORS manufacturers began to market equipment that complies with this Recommended Practice, it became obvious that the primary remaining obstacle to providing safe transportation for wheelchair-seated occupants is the wheelchair. Not only were wheelchairs not designed and tested for use as a seats in motor-vehicles, which is a use that is mandated by federal legislation, but many wheelchair manufacturers had begun labeling their wheelchairs with statements such as “Not for use in motor vehicles” or words to that effect. Clearly this is not a reasonable option for thousands of wheelchair users, and was being done by wheelchair manufacturers in an attempt to defray liability in the event that a wheelchair-seated occupant was injured in a motor-vehicle accident.
In response to this situation, in 1995 a new Working Group was formed under the Wheelchair Standards Subcommittee of ANSI/RESNA to develop a voluntary wheelchair standard that addresses design and performance issues of wheelchairs that will offer more suitable and safer seating in motor vehicles. ANSI (American National Standards Institute) is a well recognized standards-setting organization in the U.S. ANSI also serves as the U.S. representative on committees of the International Standards Organization (ISO), which sets technical standards on a world-wide scale. Within the U.S., ANSI has assigned standards development authority for wheelchairs and related equipment to the Rehabilitation Engineering and Assistive Technology Society of North America (RESNA).
The results of efforts by the ANSI/RESNA Standards Committee on Wheelchair Transportation (SOWHAT) is Section 19 ANSI/RESNA WC/Volume 1 Wheelchairs for Use in Motor Vehicles, or simply WC19, which was completed and approved in May 2000. ANSI/RESNA WC19 is a fairly comprehensive standard that addresses many issues of wheelchair design and performance. To summarize, however, the two most important requirements are:
- that a wheelchair provide four easily accessible securement points (or tiedown points) with very specific geometry (Sections 4.5 - 4.8), and
- that the wheelchair is successfully crash tested at 30 mph when secured by a four-point strap-type tiedown, and loaded with an appropriate size anthropomorphic test dummy representing the intended size and mass of wheelchair user (Section 5.3 and Annex A).
Wheelchairs that comply with this standard are referred to as WC19-compliant wheelchairs, or wheelchairs with the transit option. (See FAQ: Question A-13 for information on how to purchase complete standard).
More recently, RESNA’s SOWHAT became
a RESNA committee and is now referred to as RESNA COWHAT. One of the most
important activities completed by COWHAT is the publication of Volume 4 of the
ANSI/RESNA Wheelchair Standards: Wheelchairs and Transportation. Volume 4 brings all standards and supporting
documents related to wheelchair transportation safety into one published
document. Volume 4 was published in
December 2012 and contains the following standards:
- WC18 - a revised and updated version
of SAE J2249, Wheelchair Tiedown and Occupant Restraint Systems for Use in
- WC19, Wheelchairs for Use as Seats
in Motor Vehicles
- WC20, Wheelchair Seating Systems for
Use in Motor Vehicles
It also contains documents that
provide specifications and engineering drawings for equipment used in the test
methods of these standards, including the surrogate wheelchair used for WTORS
testing, the surrogate wheelchair tiedown and occupant restraint (SWTORS) used
for wheelchair testing, and the surrogate wheelchair frame (SWCF) used for
seating system testing. To download these drawing packages, click here.
For more information on products that comply with these U.S. standards, and with comparable ISO standards, contact your local wheelchair supplier or wheelchair manufacturer. For more information on manufacturers that have participated in the development of industry safety standards or market products that conform to the standards requirements see FAQ: Question A-4.
A-3 What is the overall goal of the WC19 compliant wheelchair and WTORS standards?
The overall goal of the RESNA Volume 4 standards is to provide the wheelchair user with the opportunity and the option to use equipment (i.e., a wheelchair seat, a wheelchair, a wheelchair securement system, and an occupant restraint) that is comparable in design and performance to seats and restraint systems available to able-bodied travelers in motor vehicles. It is not necessarily the goal of these standards to provide a comparable level of injury risk prevention for wheelchair occupants to that of the able-bodied population. Injury risk is a function of many biomechanical factors such as: body size, body condition and occupant age. When varying levels of disability are added to these factors, it is most likely that the wheelchair occupant will be at higher risk of injury then a person without a disability. It is also not the goal of WC19 to regulate or require the use of WC19-compliant wheelchairs in the real world. While there is little doubt that the use of WC19 wheelchairs, along with WC18-compliant WTORS and recommended transportation procedures, will increase the level of occupant safety and crash protection available to wheelchair users during transit, the decision to purchase and use a standards compliant wheelchair is at the discretion of the wheelchair user and other consumers.
A-4 What is the basis for these RESNA wheelchair, seating system, and WTORS standards?
The requirements and provisions of the RESNA Volume 4 standards are based on some fundamental principles of occupant protection. These include the following:
- The most common cause of serious and fatal injuries is occupant contact with vehicle interior components, or with objects outside of the vehicle following or during ejection.
- The majority of serious injury-producing crashes occur during frontal impact, or when the principal direction of vehicle deceleration is in the direction of vehicle travel, or toward the front of the vehicle.
- Effective occupant protection requires effective occupant restraint by a belt-type restraint system that includes a lower-torso or pelvic/lap belt and an upper-torso shoulder belt or harness.
- Restraint belts must be positioned so that the forces applied to the occupant in a crash are primarily to the skeletal structures of the shoulders and pelvis.
- Effective occupant restraint requires that the vehicle seat is effectively secured in the vehicle seat and that it has sufficient strength to support the occupant in a seated posture during impact. These are necessary to prevent the mass of the seat from transferring to the occupant in a crash, and to enable the belt restraints to remain in their preferred locations on the pelvis and shoulders.
In addition to these fundamental principles of occupant crash protection, these standards are based on provisions, requirements, and methods in current federal safety standards, such as FMVSS 213 Child Restraint Systems and FMVSS 209 Seat Belt Assemblies. The standards are also based on a desire to minimize the costs involved in testing to the standards.
A-5 Why is it important to secure my wheelchair if other vehicle occupants are not restrained?
It has been proposed by some wheelchair users that their wheelchairs should not have to be secured in the vehicle when other able-bodied travelers are not using belt restraints. The primary flaw in this argument lies in the distinction between seat securement and occupant restraint. While it is true that occupants of some vehicles, such as transit buses and larger school buses, are not provided with belt-type restraints, or rarely use them if they are provided, it is not true that their seat is not anchored to the vehicle. Thus, the fact that occupants are not restrained does not support the position that wheelchairs should not be secured. In a crash situation, an unsecured wheelchair is an injury hazard to both the wheelchair user and other occupants of the vehicle, just as an unanchored seat would be a hazard. This is especially true for power wheelchairs that can weigh well in excess of 200 lb.
With regard to the issue of wheelchair-seated occupants and occupant restraint systems in the school bus environment, it is also important to recognize that able-bodied students in large school buses are provided frontal crash protection through "compartmentalization," which is achieved through the use of closely spaced, high-backed padded seats. Since the wheelchair-seated student is generally not provided with compartmentalization and may, in fact, be surrounded by other wheelchairs with rigid protruding components, it can easily be argued that there is a need for wheelchair-seated students to use belt-type occupant restraints to achieve a comparable level of crash protection as that available to the able-bodied student. Fortunately, FMVSS 222 now addresses the safety of the wheelchair-seated student by requiring forward-facing wheelchair stations equipped with four-point, strap-type tiedowns and three-point belt-type occupant restraint systems. (See FAQ: Question A-9 for more information on FMVSS 222)
A-6 Why is it safer to travel in larger vehicles?
The simple answer is that it is safer to travel in larger vehicles because larger vehicles tend not to be involved in higher-severity crashes. As previously noted, crash severity is typically measured as the change in speed that the vehicle experiences during an impact event. This change in speed is often referred to as the crash "delta V" and is a measure of the kinetic energy that generates the forces on the occupant that can result in injury. In fact, the energy that an occupant must deal with is proportional to delta V to the second power, or to delta V squared, so that the energy in a 30-mph delta-V crash is more than twice that of a 20-mph delta V crash (i.e., 900 is more than twice 400).
The delta V that a vehicle experiences in a crash is not only a function of how fast it is moving but it's also a function of the mass of the vehicle or object that it strikes. If two vehicles of equal mass impact head on, then both will experience essentially the same delta V, which will be close to the speed of each vehicle at the time of impact. However, when a large vehicle impacts with a smaller vehicle, the smaller vehicle will experience a greater delta V than the larger vehicle - i.e., the small vehicle may actually reverse direction during the impact whereas the larger vehicle will continue to move in the same direction at a somewhat lower speed. For these reasons of physics, and the mix of large and small vehicles on the roadways, the distributions of real-world crash severities for large vehicles is significantly different and lower from that of smaller passenger-size vehicles. For these reasons, it is generally considered safer to travel in larger vehicles. Using larger vehicles to transport heavier occupants and heavy wheelchairs is a good countermeasure to concerns about the disparity between WTORS strength and forces generated by higher wheelchair and occupant masses.
A-7: Does WC19 apply to all mobility devices and motor vehicles?
Yes. WC19 requires that wheelchairs be crash tested in frontal-impact conditions that are applicable to a passenger-size vehicle - i.e., 30 mph, 20 g. Therefore, wheelchairs that comply with WC19 can be considered suitable for occupancy in all types of motor vehicles. The standard also applies to all types of wheelchairs, as long as the wheelchair allows the wheelchair user to attain a seated position, as defined by a seatback angle of 30 degrees or less to the vertical and a seat angle of 30 degrees or less to the horizontal. If these conditions are met, any child or adult wheelchair that complies with the requirements of the standard can be labeled and marketed as a WC19 wheelchair, including manual wheelchairs, powered wheelchairs, scooters, strollers and tilt-in-space wheelchairs. For wheelchairs designed only for children under 22 kg (about six years old), additional requirements are being developed for wheelchair-anchored belt restraints that must be anchored to (i.e., integrated into) the wheelchair.
A-8: If I have a specific disability will I be at greater risk?
It is important to recognize that tolerance to injury in motor-vehicle crashes varies widely across the population. Thus, elderly people are more likely to be injured or killed in a crash than are young people, and females are often more susceptible to injury than are males. It is therefore likely that people with certain disabilities will sustain certain types of injuries more often in a crash than people without those disabilities. However, regardless of the variation in injury tolerance, all people are less likely to be injured if they are provided with effective and properly positioned belt restraints and supportive and properly secured seating.
A-9: Where can I get information about the requirements for school buses related to wheelchair transport?
The federal regulations governing the design and construction of yellow school buses are contained in Federal Motor Vehicle Safety Standard (FMVSS) 222. FMVSS 222 is administered by the National Highway Transportation Safety Administration (NHTSA). Section S5 of FMVSS-222 deals with transportation of wheelchair-seated students in school buses, and includes the following statements:
S5.4 Each school bus having one or more locations designed for carrying a person seated in a wheelchair shall comply with S5.4.1 through S5.4.4 at each such wheelchair location.
S5.4.1 Wheelchair securement anchorages. Each wheelchair location shall have not less than four wheelchair securement anchorages complying with S5.4.1 through S126.96.36.199.
S188.8.131.52 Each wheelchair securement anchorage shall have a wheelchair securement device complying with S5.4.3 attached to it.
S184.108.40.206 The wheelchair securement anchorages at each wheelchair location shall be situated so that:
- a wheelchair can be secured in a forward-facing position.
- the wheelchair can be secured by wheelchair securement devices at two locations in the front and two locations in the rear.
- the front wheel of a three-wheeled wheelchair can be secured.
S220.127.116.11 Each wheelchair securement anchorage shall be capable of withstanding a force of 13,344 Newtons applied as specified in paragraphs (a) through (d) of this section. When more than one securement device shares a common anchorage, the anchorage shall be capable of withstanding a force of 13,344 Newtons multiplied by the number of securement devices sharing that anchorage.
- The initial application force shall be applied at an angle of not less than 30 degrees, but not more than 60 degrees, measured from the horizontal. (see figure 4)
- The horizontal projection of the force direction shall be within a horizontal arc of +45 degrees relative to a longitudinal line, which has its origin at the anchorage location and projects rearward for an anchorage whose wheelchair securement device is intended to secure the rear of the wheelchair. (see figure 4)
- The force shall be applied at the onset rate of not more than 133,440 Newtons per second.
- The 13,344 Newton force shall be attained in not more than 30 seconds, and shall be maintained for 10 seconds.
S5.4.2 Wheelchair securement devices. Each wheelchair securement device shall:
- If incorporating webbing or a strap
- comply with the requirements for Type 1 safety belt systems in S4.3, S4.3, and S4.4(a) of FMVSS No. 209, Seat Belt Assemblies; and
- provide a means of adjustment to remove slack from the device.
- If not incorporating webbing or a strap, limit movement of the wheelchair through either the equipment design or a means of adjustment.
S5.4.3 Wheelchair occupant restraint anchorages share S18.104.22.168 Each wheelchair location shall have:
- not less than one anchorage for the upper end of the upper torso restraint; and
- not less than two floor anchorages for wheelchair occupant pelvic and upper torso restraints.
S22.214.171.124 Each wheelchair occupant restraint floor anchorage shall be capable of withstanding a force of 13,344 Newtons applied as specified in paragraphs (a) through (d). When more than one wheelchair occupant restraint share a common anchorage, the anchorage shall be capable of withstanding a force of 13,344 Newtons multiplied by the number of occupant restraints sharing that anchorage.
- The initial application force shall be applied at an angle of not less than 45 degrees nor more than 80 degrees, measured from the horizontal (see Figure 5).
- The horizontal projection of the force direction shall be within a horizontal arc of +45 degrees relative to a longitudinal line, which has its origin at the anchorage and projects forward. (see Figure 5.)
- The force shall be applied at an onset rate of not more than 133,440 Newtons per second.
- The 13,344 Newton force shall be attained in not more than 30 seconds, and shall be maintained for 10 seconds.
- When a wheelchair securement device and an occupant restraint share a common anchorage, including occupant restraint designs that attach the occupant restraint to the securement device or the wheelchair, the loads specified by
S126.96.36.199 and S188.8.131.52 shall be applied simultaneously, under the conditions specified in S54.3.2 (a) and (b). (see Figure 6.)
S184.108.40.206 Each anchorage for a wheelchair occupant upper torso restraint shall be capable of withstanding a force of 6,672 Newtons applied as specified in paragraphs (a) through (d).
- The initial application force shall be applied at a vertical angle of not less than zero degrees, but not more than 40 degrees below a horizontal plane, which passes through the anchorage. (see Figure 7.)
- The projection of the force direction onto the horizontal plane shall be between zero and 45 degrees as measured from a longitudinal line with its origin at the anchorage and projecting forward. (see Figure 7.)
- The force shall be applied at the onset rate of not more than 66,720 Newtons per second.
- The 6,672 Newton force shall be attained in not more than 30 seconds, and shall be maintained for 10 seconds.
S5.4.4 E Wheelchair occupant restraints
- Each wheelchair location shall have wheelchair occupant pelvic and upper torso restraints attached to the anchorages required by S5.4.3.
- Each wheelchair occupant restraint shall comply with the requirements for Type 2 safety belt systems in S4.2, S4.3, and S4.4 (b) of FMVSS No. 209, Seat Belt Assemblies.
A-10: What does ADA say about wheelchair transport on public transit vehicles?
The Americans with Disabilities Act (ADA), signed into law in 1990 by President George Bush Sr., does contain requirements specific to wheelchair access, location, and the strength of wheelchair tiedown devices. An excerpt from the ADA follows:
(d) Securement devices
(1) Design load. Securement systems on vehicles with GVWRs of 30,000 pounds or above, and their attachments to such vehicles, shall restrain a force in the forward longitudinal direction of up to 2,000 pounds per securement leg or clamping mechanism and a minimum of 4,000 pounds for each mobility aid. Securement systems on vehicles with GVWRs of up to 30,000 pounds, and their attachments to such vehicles, shall restrain a force in the forward longitudinal direction of up to 2,500 pounds per securement leg or clamping mechanism and a minimum of 5,000 pounds for each mobility aid.
(2) Location and size. The securement system shall be placed as near to the accessible entrance as practicable and shall have a clear floor area of 30 inches by 48 inches. Such space shall adjoin, and may overlap, an access path. Not more than 6 inches of the required clear floor space may be accommodated for footrests under another seat provided there is a minimum of 9 inches from the floor to the lowest part of the seat overhanging the space. Securement areas may have fold-down seats to accommodate other passengers when a wheelchair or mobility aid is not occupying the area, provided the seats, when folded up, do not obstruct the clear floor space required.
(3) Mobility aids accommodated. The securement system shall secure common wheelchairs and mobility aids and shall either be automatic or easily attached by a person familiar with the system and mobility aid and having average dexterity.
(4) Orientation. In vehicles in excess of 22 feet in length, at least one securement device or system required by paragraph (a) of this section shall secure the wheelchair or mobility aid facing toward the front of the vehicle. In vehicles 22 feet in length or less, the required securement device may secure the wheelchair or mobility aid either facing toward the front of the vehicle or rearward. Additional securement devices or systems shall secure the wheelchair or mobility aid facing forward or rearward. Where the wheelchair or mobility aid is secured facing the rear of the vehicle, a padded barrier shall be provided The padded barrier shall extend from a height of 38 inches from the vehicle floor to a height of 56 inches from the vehicle floor
with a width of 18 inches, laterally centered immediately in back of the seated individual. Such barriers need not be solid provided equivalent protection is afforded.
(5) Movement. When the wheelchair or mobility aid is secured in accordance with manufacturer's instructions, the securement system shall limit the movement of an occupied wheelchair or mobility aid to no more than 2 inches in any direction under normal vehicle operating conditions.
(6) Stowage. When not being used for securement, or when the securement area can be used by standees, the securement system shall not interfere with passenger movement, shall not present any hazardous condition, shall be reasonably protected from vandalism, and shall be readily accessed when needed for use.
(7) Seat belt and shoulder harness. For each wheelchair or mobility aid securement device provided, a passenger seat belt and shoulder harness, complying with all applicable provisions of 49 CFR part 571, shall also be provided for use by wheelchair or mobility aid users. Such seat belts and shoulder harnesses shall not be used in lieu of a device which secures the wheelchair or mobility aid itself.
For more information see: http://www.access-board.gov/transit/html/vguide.htm
A-11: Where can I get more detailed information about the activities of the standards working groups (draft standards, meeting minutes, reference documents, etc.)?
A-12: How can I help move this effort forward more quickly?
Many manufacturers of wheelchairs, seating systems, and WTORS have actively participated in the development of the standards as well as in testing their products to the standards. This has been a significant financial investment by the manufacturers to improve the transport safety of their products. Since compliance with the standards is voluntary, there are unfortunately still products that are being marketed that are clearly intended for use in motor vehicles that have not been tested to the standards. The single most effective way to rectify this problem is for consumers, parents, caregivers and prescribers to request, and whenever possible, purchase only products that have been tested to one or more of the appropriate transport standards. If the product is in compliance, it should be so labeled on the product.
For those interested in becoming more directly involved in the standards development process, there is a way that you can be added to the e-mail lists or working groups. The standards working groups are always open to manufacturers, researchers, transporters, consumers and clinicians who wish to contribute their experiences and participate in the research, testing, discussions, and debates that move the work forward. Although several of the key standards have now been completed, all standards are reviewed at least every five years, and are modified more frequently, if necessary. Secondly, new areas of standards development are now underway to in the initial development effort. For more information on how to become involved:
- For the RESNA Committee on Wheelchairs and Transportation (COWHAT) in the USA, contact Miriam Manary, Chair, RESNA COWHAT at firstname.lastname@example.org
- For International (ISO) Working Group or WG-6, contact the chair, Aleid Hekstra at email@example.com
A-13: Where can I get a complete copy of the current industry standards?
In the United States:
Download the order form from the RESNA website here or contact RESNA using the information below.
Source: RESNA: 1700 North Moore Street, Suite 1540, Arlington, VA 22209-1903
- Z604: Transportable Mobility Aids - (Feb. 1997)
- Z605: Mobility Aid Securement and Occupant Restraint Systems – (Feb. 1997)
As of March 2002, both Z604 and Z605 are under revision, which should align them more closely with the U.S. and ISO counterparts.
International Standards or ISO:
For a complete description of the ISO wheelchair transportation safety standards, click here.
Purchase Standards at: http://www.iso.org/iso/home.htm
A-14: Where can I get more information about products that conform to the industry standards related to wheelchair transport safety?
For more information on the products from specific manufacturers, see the listing of compliant wheelchairs, seating systems, and WTORS products here. The Ride Safe brochure also lists product manufacturers who have participated in standard development and/or successfully crash tested products.
A-15: What is the Rehabilitation Engineering Research Center (RERC) on Wheelchair Transportation Safety (WTS)?
This Rehabilitation Engineering Research Center (RERC) was a five-year project (November 2006 to October 2011) funded by the National Institute of Disability and Rehabilitation Research (NIDRR). It focused solely on the issues of transportation safety for occupants of motor vehicles who remain seated in their wheelchair. The RERC on WTS was a partnership between the University of Michigan Transportation Research Institute, the University of Louisville's Speed School of Engineering, the University of Pittsburgh's Department of Rehabilitation Science and Technology and the University of Colorado's Assistive Technology Partners.
In addition to focusing on research and development activities concerned with occupant protection for wheelchair travelers in side and rear impacts, the RERC also addressed issues of improved restraint systems and wheelchair seating systems. In addition, however, the RERC expended considerable effort on the development and implementation of additional standards and on the dissemination of information related to these standards. Its goal was to focus its resources on the issues surrounding providing safer transportation and improved crash protection for wheelchair-seated travelers. The funding period for the RERC on WTS is over and the RERC is no longer conducting research, but much of the information on this UMTRI website is carried over and updated from the RERC on WTS website: http://www.rercwts.org.
Group B. Questions: Wheelchair Tiedown and Occupant Restraint Standards (WTORS)
B-1: What are the requirements for tiedown and occupant restraint products to comply with the wheelchair tiedown and occupant restraint standards (WC18 and ISO 10542)?
Although there are some differences between the US WC18 and the ISO 10542-1 standards, the general requirements and test methods are essentially identical and may be summarized as follows:
The standards apply to WTORS:
- that include all different types of wheelchair securement systems,
- with belt-type occupant restraint systems,
- for both passengers and drivers (adults only-ISO),
- for use in both public and private vehicles,
- for use with all wheelchairs including scooters, and
- for use with forward-facing wheelchairs in the vehicle.
The standards require that:
- pelvic and shoulder restraints be used in the tests and recommend use of both belts during transport, especially in vehicles that have occupant restraint belts normally installed,
- a dynamic 30 mph (48kph) frontal-impact test be used to confirm the performance of the WTORS,
- the end fittings on tiedown straps meet a specific design so that the end fitting will readily latch to the mating receptacle on the transport-compliant wheelchair,
- the product be permanently labeled as to the test passed,
- instruction and warnings be provided for both installers and users.
B-2 What is the difference between an integrated and an independent occupant restraint system?
An independent occupant restraint system is a vehicle-anchored belt restraint system that is anchored "independent" of the occupant’s seat or wheelchair to the vehicle structures. In an integrated restraint system, the anchor points for the restraint system are on the seat or wheelchair - i.e., it is a seat- or wheelchair-integrated restraint system. Integrated restraint systems are becoming more common in automobiles because the belts generally fit and perform better when they are anchored closer to the occupant on the vehicle seat. It is also possible to have a partially integrated restraint system, where only the pelvic belt is anchored to the wheelchair or vehicle seat, but the upper end of the shoulder belt is anchored to the side-wall of the vehicle. This, in fact, is what is required as an option on all WC19 wheelchairs. If a wheelchair user chooses this option, he/she can have a pelvic/lap belt installed on the wheelchair that will include hardware for a standard interface connection to the lower end of a vehicle-anchored shoulder belt.
It is also possible to have a totally integrated belt restraint system where the anchor points for both the upper and lower torso belts are on the wheelchair. However, the upper anchor points will place high forces on the upper part of a wheelchair backrest in a frontal crash, and most wheelchair backrests would not be able to withstand these forces without significant design modifications. The totally integrated restraint system is probably most feasible and most important for smaller children, but the partially integrated pelvic/lap belt should be feasible for most wheelchair users and will improve pelvic belt performance, reduce the tendency for lap-belt "submarining" (i.e., going under the lap belt), and reduce interference with the wheelchair user's personal space when installing a belt restraint in a motor vehicle. For these reasons, WC19 requires wheelchairs to provide the wheelchair user with the option of using a wheelchair-anchored pelvic belt.
Beginning in December 2015 (three years after publication of WC18), WTORS for general use will be required to perform an additional crash test where the ATD is restrained by a surrogate pelvic (lap) belt anchored to the test wheelchair, thereby increasing the frontal-impact loads on the rear tiedown straps of four-point, strap-type tiedown systems, or on other types of securement devices.
Note: The term restraint is used exclusively in reference to the wheelchair occupant and the term tiedown or securement is used exclusively in reference to the wheelchair. A wheelchair is not restrained but is tied down or secured. An occupant is not secured, but is restrained in a motor vehicle.
B-3 What do I do with a very heavy wheelchair? Will the wheelchair tiedowns be strong enough?
WC18 requires dynamic testing of wheelchair securement systems in a 30-mph frontal impact using a rigid surrogate wheelchair that weighs 187 lb. Clearly, the static mass of some commercial wheelchairs is greater than this surrogate wheelchair. In addition, if wheelchair occupants use seatbelt restraints that anchor to the wheelchair (i.e., integrated) or even wheelchair-attached postural belts, the forces on the wheelchair securement system may be higher in a 30-mph crash than those to which the securement system has been tested.
What this means is that, under some relatively severe crash conditions, the user of a very heavy wheelchair may be at somewhat greater risk than the user of a lighter wheelchair. However, in considering this apparent disparity between WC18-required WTORS strength and potential real-world loading scenarios, it is important to remember that the likelihood of a 30-mph crash is low even in vans and minivans. The likelihood is even lower in larger vehicles such as school buses and transit buses. Thus, for the large majority of frontal crashes, the user of a very heavy wheelchair that meets WC19 will still be provided with effective wheelchair securement. If the desire is to reduce the risk to the wheelchair occupant in higher severity crashes when traveling in vans and minivans, then additional tiedown straps can be installed for use with a heavier WC19-compliant wheelchair.
Remember that WC19 requires that wheelchairs with a mass up to 400 lb be successfully crash tested at 30 mph. Thus, heavy WC19-compliant wheelchairs, regardless of their mass, have demonstrated that they can deal with the forces generated by their own mass in a 30-mph frontal crash using the securement points provided and specified in the manufacturers literature. Therefore, the use of a heavy wheelchair that has been tested to the WC19 standard will reduce the risk of ineffective wheelchair securement for most real-world crashes.
Finally, the disparity between the dynamic strength of wheelchair tiedowns and the potential loads imposed by heavy wheelchairs continues to be concern. It is useful to realize that there has been, and continues to be, a much greater disparity between the strength of WC18-compliant tiedowns and most non-WC19-compliant wheelchairs that are secured in vehicles by these tie-downs. In these situations, the wheelchair is the weak link in the system. This issue of disparity in strength between wheelchair and securement system is much more prevalent and a much greater concern in occupant safety for wheelchair-seated travelers than is the disparity between the potential loads imposed on wheelchair tiedowns by heavy wheelchairs in high-severity crashes. Thus, while the concern for strength limitations of wheelchair tiedowns should be a consideration when transporting occupants in heavy wheelchairs, it needs to be kept in the proper perspective with regard to the overall merits and benefits of using wheelchairs that comply with WC19.
B-4: If I use a very heavy wheelchair that may exceed the capacity of existing tiedown devices, when should I use additional tiedown straps?
The question of when and whether to use additional tiedown straps is up to the wheelchair user, the transit provider, etc. and depends on a number of factors. The answer probably also depends on whether the wheelchair complies with a transport standard (WC19), as will be explained shortly. For heavy wheelchairs that do NOT comply with the transport standard, the more straps the better. However, finding four suitable securement points (much less, more than 4!) is problematic on many wheelchairs, and of course none of these additional securement points have been dynamically tested.
The need for additional straps also depends on the type of vehicle and transit mode. For large city buses and large school buses, more than four straps is probably not warranted, especially for transport-tested wheelchairs, since this type of vehicle is very unlikely to ever experience a 30-mph crash to which tiedown straps that comply with tiedown standards have been tested.
Another factor that could influence the decision about whether and when to use additional tiedowns is whether the occupant is restrained by belts that anchor to the wheelchair (i.e., integrated restraints) or restraint belts that anchor directly to the vehicle. In other words, when the occupant restraint loads are combined with the heavy wheelchair loads, the combination may exceed the capacity of only two rear tiedown straps.
For a WC19 compliant wheelchair, the standard allows wheelchairs that weigh more than 275 lbs. to provide for more than four securement points (e.g., 3 or 4 in the back). It also requires that the manufacturer's presale literature indicate the number of securement points and tiedown straps used in the frontal impact test, if the number is greater than the minimum of four. Note that wheelchairs weighing less than 275 lb must pass the test with only four securement points and that wheelchairs weighing more than 275 lbs don't have to provide more than four securement points.
However, whether or not a wheelchair has been tested with four, or more than four tiedown straps, the decision of whether to use four or more tiedowns in the real world may be different. For example, if a 280 lb wheelchair is tested using five securement points with three of these for rear securement, a transit provider for large city buses or large school buses might decide to use only two of these rear securement points, since a large vehicle is extremely unlikely to ever experience anything close to a 30 mph impact. Similarly, if a 200 or 250 lb wheelchair is used in a van-sized vehicle that travels the highways, the user or transit provider might decide to use four rear tiedown straps instead of just two, particularly for occupants with a pelvic belts anchored to their wheelchairs. This can be done because the geometry of the securement points required by the standards will allow two tiedown straps to be attached to each of the rear securement points.
In summary, the questions about whether to use more than four tiedown straps for heavier wheelchairs and for situations with wheelchair-integrated restraints, and at what wheelchair mass to implement additional tiedowns do not have simple answers. The answers depend not only on the type of vehicle and travel mode, but also on how much additional risk you are willing to trade off for the convenience of using only four tiedown straps instead of more than four straps. If you are very conservative and don't want any additional risk, and are willing to put up with additional time and effort to secure a wheelchair, then you might decide to use four rear tiedown straps in a van-sized vehicle whenever the wheelchair mass exceeds 250 lbs. However, if you are willing to take some additional risk (maybe not protect the wheelchair occupant quite as well in 25 - 30 mph impacts, because reduced time and effort is very important) then you might not use more than two rear tiedown straps for wheelchairs that weigh as much as 250 lb in a van-sized vehicle. At no time, however, should one use less than four transport-tested tiedown straps, two in the rear and two in the front.
B-5: If I have a wheelchair with a tilting (tilt-in-space) seat frame, what is the best way to secure the wheelchair to the vehicle?
The answer to this question depends somewhat on whether you are dealing with a WC19-compliant wheelchair or a non-WC19 wheelchair. For non-WC19 wheelchairs that do not have designated securement points it is generally recommended that both the front and rear securement points be either on the front and back of the seat or on the front and back of the wheelchair frame or base (presuming it is possible to find four relatively strong attachment points on the wheelchair frame on either part of the wheelchair). This is done to minimize the chance of extreme slack developing in the tiedown system which would occur if the seat tilt angle changes, resulting in large changes in distance between points on the wheelchair base at one end of the wheelchair and points on the wheelchair seat at the other end. In addition, it is recommended that these four points be on the seat, since these points will usually provide slightly steeper tiedown strap angles that increase wheelchair stability and reduce upward movement of the wheelchair in a crash situation.
For WC19-compliant wheelchairs, however, it is not as important for all four securement points to be on the seat or on the base. This is because a WC19-compliant tilt-in-space wheelchair will have been dynamically strength tested using the securement points provided by the manufacturer, wherever they are. It is, however, still preferable for the securement points to be located high on the wheelchair base or seat frame, rather than down low near the floor (note the minimum height allowed by WC19 is 100 mm = 4”) to increase wheelchair stability during transit and reduce upward motion and pivoting of the wheelchair in a frontal crash. However, even though manufacturers are placing securement points lower on some WC19-compliant wheelchair frames than is preferred, these wheelchairs have complied with the WC19 test and have therefore demonstrated effective crash performance with these locations.
Group C. Questions: Transport Wheelchair Standards (RESNA WC19, ISO 7176-19)
C-1 What is WC19 and what is its purpose?
The WC19 standard establishes the minimum wheelchair design and performance requirements that improve the safety and security of wheelchair-seated occupants of motor vehicles during normal transportation, but especially in the event of a vehicle crash. A wheelchair that complies with WC19 is also referred to as a WC19 wheelchair or as a wheelchair with the transit option. There is a complete section of information on wheelchairs that meet this standard on this website here, as well as a frequently updated listing of crash-tested wheelchairs and seating systems here.
There are other RESNA standards that address the issues of wheelchair design and performance such as strength, durability, stability, etc. This body of work is currently managed by Peter Axelson, Chair of the RESNA Technical Standard Board. The development of standards requires significant work from a groups of dedicated individuals who represent the viewpoints of consumers, engineers and manufacturers. Wheelchair Standards Volume I (1998) includes all wheelchairs and Volume II (1998) contains additional standards that apply to wheelchairs with electrical systems.
These are "voluntary" standards in that they are not mandated by federal or state laws, and compliance of a product with the requirements of each standard is "self certified" by the wheelchair manufacturer. WC19, or more correctly, Section 19 of RESNA Wheelchair Standards, Volume 4: Wheelchairs and Transportation: Wheelchairs for Use in Motor Vehicles (Section 19, RESNA WC-4:2012) is the first and, so far, only RESNA wheelchair standard that addresses issues of wheelchair design and performance that are related to the use of a wheelchair for seating in a motor vehicle.
The original version of WC19, Section 19 ANSI/RESNA WC/Volume 1: Wheelchairs for Use in Motor Vehicles, was published as a supplement to Volume I in April 2000 because it was not ready when Volume I and II were originally published.
In general, wheelchair standards have been reorganized so they will exist within the following volumes.
- Volume I: Manual Wheelchairs
- Volume II: Powered Wheelchairs
- Volume III: Wheelchair Seating
- Volume IV: Wheelchairs and Transportation (published Dec 2012).
Unlike other wheelchair standards, WC19 is not perfectly harmonized with the ISO wheelchair transportation standard because it was developed before the ISO equivalent. They are however moving toward harmonization. See Question C23 for more information on this topic.
C-2 Why is WC19 needed?
Providing a safe ride for motor-vehicle occupants, including their protection in a vehicle crash, is a "systems" problem. The "system" involves the vehicle, the occupant, the seat, the seat anchorage, and the occupant restraint system. For vehicle occupants who remain seated in a wheelchair in a motor vehicle, the wheelchair becomes the vehicle seat and the seat anchorage is the wheelchair tiedown or securement system.
With the completion of SAE J2249 Wheelchair Tiedowns and Occupant Restraint Systems (WTORS) for Use in Motor Vehicles (now revised and updated as RESNA WC18), the wheelchair became the primary "weak link" in this system and the primary obstacle to providing wheelchair-seated occupants safer transportation and a reasonable level of occupant protection in a crash. If the seat or wheelchair is not effectively secured to the vehicle and does not offer the occupant effective support in a frontal crash, then the occupant-restraint system cannot provide effective restraint and, in fact, is much more likely to cause injury to the occupant by applying restraining forces on soft and vulnerable parts of the body, such as the abdomen.
C-3 What is the scope of WC19 and what does it require?
WC19 addresses a number of wheelchair design and performance issues related to protection of forward-facing occupants in frontal crashes. Most importantly, it requires that wheelchairs provide four easily accessible securement or attachment points for anchoring the wheelchair in place, facing forward in the vehicle using a WC18-compliant four-point, strap-type tiedown system. It further requires that an appropriately-sized crash dummy (i.e., anthropomorphic test device or ATD) sit in the wheelchair and that it be dynamically crash tested in a 30-mph frontal impact sled test.
However, the standard also addresses several other wheelchair design and performance issues, including requirements that:
- a WC19-compliant wheelchair shall provide the wheelchair user with the option of using a wheelchair-anchored pelvic/lap restraint belt, and shall be crash tested with such a belt restraining the lower torso of the ATD,
- the wheelchair shall be tilt tested and rated for lateral stability, and rating of good, acceptable, or poor shall be disclosed in the wheelchair manufacturer's presale literature and user instructions,
- the wheelchair structure shall allow clear paths between securement points and typical vehicle anchor points,
- the wheelchair shall be tested and receive a rating of at least 'acceptable' for the ease of applying a vehicle-anchored belt
restraint on the occupant and the degree to which proper belt positioning is
- the wheelchair and wheelchair-anchored belt restraints shall be labeled as complying with WC19 with the symbol below,
- wheelchair-anchored postural belts provided by the manufacturer shall be labeled as "not for use as an occupant restraint in a motor vehicle," and
- the wheelchair manufacturer shall provide information and warnings on proper securement and restraint procedures in product literature.
C-4 What is the benefit to purchasing a wheelchair that complies with WC19?
Purchase and use of WC19-compliant wheelchairs will greatly enhance the ease and ability to secure the wheelchair in a motor vehicle using a four-point, strap-type tiedown system and, most importantly, will reduce the risk of injury to both the wheelchair user and other vehicle occupants in the event of a frontal crash. Although WC19 does not yet specifically address wheelchair crash performance for rear or side impacts, or for vehicle rollovers, use of a WC19 wheelchair is expected to significantly reduce injury risk for these crash modes as well.
C-5 What is different about WC19 wheelchairs?
Other than the addition of four easily accessible securement points on the wheelchair frame, the wheelchair-anchored pelvic belt restraint, and the WC19-required labeling on the wheelchair frame and belts, these wheelchairs are not noticeably different from non-WC19-compliant wheelchairs. In many cases, the changes needed to redesign a non-WC19-compliant wheelchair so that it can become a WC19-compliant wheelchair are minor and involve modifications to structural design and changes in materials that will not be apparent to the wheelchair user or an observer.
The 30-mph frontal impact specified in Annex A of WC19 imposes significant forces on the wheelchair and its securement points. These forces are functions of the wheelchair mass, the locations of occupant-restraint anchorages, the locations of the securement points on the wheelchair, and the size of the wheelchair occupant. However, it is important to know that wheelchairs do not need to be "built like a tank" to comply with the crashworthiness requirements of WC19. In fact, some of the lightest-weight stroller-type wheelchairs perform the best in the 30-mph frontal impact crash test, and fully comply with the frontal-impact performance requirements of WC19.
C-6 Does designing a wheelchair to comply with WC19 transport standards conflict with the other features and functions of wheelchairs that are important to wheelchair users on a daily basis?
This question is prompted by the fact that some individuals are beginning to express concern that producing a WC19-compliant wheelchair means sacrificing some other features of a wheelchair that may be more important to the wheelchair user on a daily basis. The concern is that they will need to trade off safety in a motor vehicle for functionality during everyday living.
There is no evidence to support such concerns or claims. Other than having four easily visible and accessible dynamically tested securement points, having less injury producing protrusions, and being more compatible with occupant restraints, wheelchairs that are WC19 compliant should be little different in design and function than non-WC19 compliant wheelchairs. The features that give the wheelchair improved dynamic strength should be essentially invisible to the user, and should also improve overall wheelchair durability of the wheelchair. However, for ultralight designs there will be a slight increase in weight that may prove important to an active user. Many users of ultralight wheelchairs are able to transfer out of the wheelchair and into the vehicle seat with its great protection.
Perhaps another requirement of WC19 that might conflict with other wheelchair design features and functions is the backrest height. Wheelchairs with very low or very weak backrests may not comply with the rebound-loading requirement of WC19, which requires that wheelchair backrests provide effective support for the ATD when it rebounds from loading the belt restraints in the frontal-impact test. However, most users of low-back wheelchairs, such as sport or ultralight wheelchairs, are capable of transferring to the vehicle's standard seats. These individuals should make this transfer and not remain seated in their wheelchairs when traveling in a motor vehicle. In this case, it would not be necessary for the user to have a WC19 compliant wheelchair.
C-7: What is the basis for the 30-mph frontal-impact requirement of WC19?
As indicated above, the WC19 wheelchair and WTORS standards are based on existing federal safety standards for passenger vehicles. Although a dynamic side-impact test was implemented as a federal safety standard a few years ago, the frontal crash test has historically been the US government's first and primary priority in occupant protection because more than half of all serious and fatal injuries occur in frontal crashes. Thus, FMVSS 208 Occupant Crash Protection requires that vehicles are barrier crash tested at 30 mph. In addition, FMVSS 213 Child Restraint Systems requires that child safety seats are sled-impact tested at 30 mph. Following the precedents set by these federal safety standards, both national and international standards for wheelchairs designed for use in transportation and WTORS have used a 30-mph crash pulse.
It should be noted that 30 mph refers to the change in vehicle speed or "delta V" experienced by the vehicle in a crash, and not to the speed of the vehicle prior to the crash. While vehicles typically travel at speeds considerably in excess of 30 mph, a 30-mph delta-V impact test represents about a 95th-percentile crash severity in terms of real-world frontal crashes for passenger cars. That is, about 95% of real-world frontal crashes of passenger cars, minivans, and sport utility vehicles are less than 30 mph in severity. For larger vehicles, such as buses and school buses, a 30-mph frontal impact is an even less likely event. However, the test requirements of these wheelchair and WTORS standards are based on the assumption that wheelchair users will, at sometime, be seated in van-size vehicles and that most types of WTORS could be installed in smaller passenger vehicles. The standards therefore require that products be tested for this "worst-case" crash-severity situation of 30-mph, with the understanding that some, but relatively few, real-world crashes will be more severe.
C-8: Why does WC19 require that wheelchairs be designed for securement using a four-point, strap-type tiedown?
In addition to making wheelchair securement more effective and to ensuring a reasonable level of seat integrity and occupant support in a 30-mph frontal crash, the members of the ANSI/RESNA Subcommittee on Wheelchairs and Transportation (SOWHAT) who developed WC19 believed that it was equally important to ensure compatibility between the method of wheelchair securement provided on the wheelchair and the securement system available in the vehicle. Without compatibility, there is little value to having a WC19 wheelchair. For public transportation environments, including school buses, the four-point, strap-type tiedown system is currently the only system that can adapt to the wide variety of wheelchair types and sizes that are transported in a given vehicle each day. It is, in fact, today's only "universal" wheelchair securement system. The four-point, strap-type tiedown is also a securement system that has proven to be effective in securing a wide range of wheelchair makes and models in 30-mph frontal impact crashes. It is for these reasons that WC19 requires a wheelchair to provide for securement in vehicles using the four-point, strap-type tiedown.
C-9: Where should wheelchair securement points be located?
"Securement point" is the terminology used in WC19 to identify those places on the wheelchair where the tiedown straps or another type of tiedown system are attached. In general, it is preferable that the securement points be located high enough so that the rear tiedown straps form an angle of about 30 to 45 degrees to the horizontal and the front tiedown straps are between 30 and 60 degrees. However, what is more important than the height of the securement points, is the strength of the securement points or the parts of the frame to which the tiedowns are attached. Thus, if stronger securement points can be found on the lower portions of the frame than on the upper frame or seat, the lower securement points may be preferable.
In this regard, some people have become concerned that wheelchair manufacturers are placing the securement points too low on WC19-compliant wheelchairs. In developing WC19, the ANSI/RESNA Subcommittee agreed to allow securement points to be as low as 100 mm (about 4 inches) from the ground so that wheelchairs with relatively low frame structures could be modified to comply with relatively few changes in structural design. While wheelchair stability during normal transit (and especially in a crash) will generally be better with higher securement points, the low securement points provided on a WC19-compliant wheelchair must have provided effective wheelchair securement under relatively severe frontal impact conditions. At least this should be true when tested with an independent, vehicle-anchored, belt restraint system. Thus, even lower securement points on WC19 wheelchairs should represent a significant reduction in injury risk over any securement points on non-WC19-compliant wheelchairs. However, with the requirement for testing wheelchairs using a wheelchair-anchored belt restraint, it is likely that the rear securement points will need to be raised higher on some wheelchairs in order to comply with the dynamic strength requirements of WC19.
C-10: Are there special considerations for locating securement points on wheelchairs with tilt-in-space seating systems?
The answer to this question is somewhat dependent on whether one is referring to a WC19-compliant wheelchair or to a non-WC19-compliant wheelchair. For non-WC19-compliant tilt-in-space wheelchairs that do not have four securement points and that have not been crash tested to WC19, it has always been recommended that all four (i.e., two front and two rear) securement points be either attached to the seat or attached to the base of the wheelchair frame. This recommendation is made to minimize the chance for significant slack developing in the tiedown straps during a crash, which would result in large wheelchair movements, or possibly in the wheelchair coming free from one or more of the tiedown straps. This slack could develop, for example, if the securement points at the front are on the base and those at the back are located on the seat behind the pivot point. In a frontal crash, the forces on the back of the seat would be likely to cause the seat to tilt further rearward, thereby reducing the distance between the rear securement points and the rear anchor points, resulting in slack in a tiedown system that depends on tension to function effectively.
If four securement points are available on the seat such that the two front securement points are forward of the seat pivot point and the two rear securement points are rearward of the seat pivot point, this approach is generally recommended, over using four securement points on the base. Securement points on the seat are likely to be higher and thereby result in more optimal tiedown strap angles between 30 and 45 degrees to the horizontal. More importantly, the tension between the front and rear tiedown straps will stabilize the seat about the seat pivot point and maintain the orientation of the seat without depending on the strength of the tilt locking mechanism.
If four suitable securement points cannot be found on the tilt-in-space seat, then all four should be located on the strongest available points on the frame of the wheelchair base. Although the rotational stability of the seat will be completely dependent on the tilt-in-space locking mechanism when the base is secured, there is less chance for movement between securement points on the base and anchor points in the vehicle, and therefore a better chance for effective wheelchair securement.
For WC19-compliant wheelchairs, it is not as important that all four securement points are on the seat or on the base. This is because WC19-compliant wheelchairs are dynamically tested in a 30-mph frontal impact using the securement points provided by the manufacturer. Thus, whether the securement points are on the base or the seat, the wheelchair will have demonstrated that it can be effectively secured in a severe frontal crash test.
There is, however, a potential problem if all four securement points are not located on either the base or the seat, even for WC19-compliant wheelchairs. If, after securing the wheelchair and adding tension to the tiedown straps, the seat tilt angle is manually adjusted, the tension in the tiedown straps may be lost. This would be the case, for example, if the rear securement points are on the seat and the front securement points are on the base, and the seat is tilted rearward after the four-point strap system has been tightened. Unless the attendant notices the reduced tension, and readjusts the tiedown straps, this additional slack will reduce the tiedown effectiveness and could potentially result in the wheelchair being released from one or more tiedown straps during transit.
C-11 Should wheelchair manufacturers set special limits on the weight of occupants who can use WC19 wheelchairs?
To clarify the basis for this question, WC19 specifies that the size and weight of the crash dummy used in the 30-mph frontal impact test be representative of the size and mass of the largest person for which the wheelchair is designed. Thus, if a wheelchair is designed only for use by children, then either the three-year-old (36 lb), six-year old (47 lb), or ten-year-old (80 lb) crash dummy or the 100-lb, small-adult, crash dummy would be recommended for use in the sled impact test. However, if the wheelchair is designed for use by a wide range of adults, the test specifies that a 170-lb or 50th-percentile adult male crash dummy be used. The manufacturer can also choose to use a larger 95th percentile adult male dummy that weighs about 225 lb, but this heavier dummy is not required, even though the wheelchair may be designed for and capable of being used by a person who weighs 300 lbs. or more. However, some wheelchair manufacturers seem to be saying in their literature that wheelchair users who weigh more than the crash dummy used in the frontal crash test (or in some cases more than 150 lb) may not purchase a WC19-compliant wheelchair.
The reasonable answer to this question is that the weight limit for users of WC19 wheelchairs should be no different than the weight limit for the wheelchair in general. If placing special weight limits on WC19-compliant wheelchairs (based on the mass of the crash dummy used in dynamic testing) were a reasonable approach, then General Motors and Ford should limit the sale and use of their vehicles to people who don't weigh more than the crash dummies used in federal motor-vehicle safety testing (currently about 170 lb).
This issue of placing limits on the weight of occupants who can use WC19-compliant wheelchairs raises an important and more general issue about injury risk that needs to be understood when using and applying safety standards. It is a fact of physics that the forces needed to restrain occupants with a total body mass greater than that of the crash dummy will produce higher forces in a 30-mph impact than those produced by the crash dummy in the 30-mph test of WC19. These additional forces will be imposed primarily on the occupant restraint system, and perhaps on the wheelchair securement system, and to a lesser extent on the wheelchair. Thus, the strength limits of an occupant restraint system will be reached at lower crash severities for heavier occupants than for lighter occupants, thereby placing heavier occupants at somewhat greater risk of injury in severe crashes. However, the large majority of crash situations occur at less than 30 mph, and even heavy occupants will be at much less risk of injury in the large majority of crashes if they are in a WC19 wheelchair than if they are using a wheelchair that has not been crash tested and/or provided with the WC19 option features.
Product standards usually require designing for, and testing to, a set of reasonable, but somewhat worst-case conditions that may be experienced in the real world. It is rare that a standard requires products to be tested at the absolute extreme conditions of potential real-world exposure, especially when the likelihood of that exposure is very remote, as is the case with very high-severity motor-vehicle crashes. A 170-lb crash dummy represents about a 50th percentile adult by height and weight, and the 225-lb crash dummy represents a 95th percentile male by weight or about a 97.5 percentile adult by weight. Similarly, a 30-mph frontal crash test represents about a 95th percentile frontal crash pulse for a passenger-size vehicle, such as a van or minivan, and a much higher percentile for larger vehicles. In the real world, people who ride in vehicles are exposed to a wide range of conditions and circumstances that can increase the risk of injury beyond that covered by safety testing. Impact severities can be greater than 30 mph and they can come from different directions. Older occupants are at higher risk of injury than younger occupants. Heavier occupants are at greater risk than lighter-weight occupants. People in smaller vehicles traveling at higher speeds are at greater risk of injury in a crash than people in larger vehicles and/or vehicles traveling at slower speeds. A standard cannot, and does not, provide everyone with the same risk of injury in a crash.
The bottom line is that, although the level of injury risk varies widely depending on a wide range of occupant, vehicle, and crash variables, all wheelchair users who cannot transfer from their wheelchair when traveling in a motor vehicle will be at reduced risk of injury if they are seated in a WC19-compliant wheelchair that complies with WC19, and if they are using an WC18-compliant WTORS. Heavier persons can benefit from using a WC19-compliant wheelchair just as much as people who weigh less than the crash dummy. Wheelchair manufacturers should not limit the sale of WC19-compliant wheelchairs to consumers who weigh the same or less than the crash dummy used in the tests. Weight restrictions for WC19-compliant wheelchairs should be the same as those for the design capacity of the wheelchair for normal everyday use.
C-12 Do I always need to replace a WC19 wheelchair following a crash or sudden stop?
No. Apparently some wheelchair manufacturers are putting statements in their literature that the wheelchair must be replaced if it is involved in a crash, or even if it is involved in a "sudden stop." A good rule of thumb is that components of a wheelchair may need to be replaced if the wheelchair is involved in a crash that results in the need to tow the motor vehicle from the crash scene - i.e., in a "tow-away crash." However, this does not mean that the complete wheelchair must be replaced, and it may not mean that any components need to be replaced. In fact, if the wheelchair complies with WC19, the need to replace all or part of the wheelchair following a crash is much less likely than if it is not a crash-tested WC19 wheelchair.
It is, however, important that the wheelchair manufacturer and/or wheelchair prescriber be consulted following a tow-away crash to determine the extent of structural damage, if any. In a recent University of Michigan Transportation Research Institute (UMTRI) investigation of a modified van, a 300-lb power wheelchair with WC19-like securement points was secured using a four-point, strap-type tiedown during a 20-to-25 mph frontal crash into the side of a truck. The wheelchair was effectively secured by a four-point tiedown system that complies with WC18 and sustained relatively little structural damage. In fact, a detailed inspection of the wheelchair following the crash by the wheelchair prescriber revealed that a linkage on one side of the power reclining seat back was the only component that needed to be replaced.
It is also important to understand that WC19 is currently silent on the issue of replacing a wheelchair or its components following a crash, although a future version will probably include more specific requirements for manufacturer instructions and warnings on this issue. Furthermore, even if all or part of a wheelchair needs to be replaced following a severe crash, the costs involved should be considered a small price to pay if the wheelchair performed well enough to allow the restraint system to protect the wheelchair user from serious or fatal injuries.
C-13: What tilt and recline angles are acceptable in motor-vehicle transportation and what are the potential negative consequences of reclining an occupant too much?
First of all, it should be noted that WC19 does not place any requirements on the backrest recline or seat tilt angles used to transport persons in wheelchairs. WC19 only places requirements on tilt and recline angles provided for in the wheelchair design, and on preferred and recommended tilt and recline angles that must be specified in the manufacturer's instructions and warnings to the user .
The only design requirement that WC19 places on the wheelchair is that the backrest frame is capable of being tilted to within 30 degrees of vertical and that the seat frame can be positioned within 30 degrees of horizontal. That is, WC19 requires that the wheelchair allow the wheelchair user to attain a seated posture. Stretchers, beds, and other devices that might be used with some disabled persons will therefore not comply with WC19.
WC19 also requires manufacturers of wheelchairs designed for use in transportation to provide instructions and warnings in the wheelchair literature that the wheelchair backrest should not be reclined more than 30 degrees to the vertical. This maximum ”recommended” recline angle is intended to help maintain effective performance of belt-type restraint systems by having the shoulder belts in close proximity to, and preferably in contact with, the chest and shoulders. When the torso is reclined, the distance between the shoulder belt and the occupant increases, and this results in increased forces on the occupant in a frontal crash. In addition, with a more reclined torso posture, the chest will tend to take more of the load than the shoulders, thereby increasing the probability of belt-induced thoracic injuries.
It is also preferable for the lap angle to be between 45 and 75 degrees relative to the horizontal, and at an angle of 30 degrees or more to the occupant’s thigh angle. These angles will help ensure that the lap belt remains low on the pelvis in a frontal crash, and that the potential for lap-belt induced injuries to the relatively soft abdomen is minimized.
Note that WC19 does not require the manufacturer to make a recommendation about the maximum tilt or incline angle of the seat of tilt-in-space wheelchairs. This is because limiting the backrest angle also limits the seat incline angle. While inclining a forward-facing seat has some benefit in a frontal crash in that the seat provides additional restraint for forward movement of the pelvis in a frontal crash, too much seat incline increases the possibility of the lap belt loading the softer abdomen. However, 30 degrees of seat incline relative to the horizontal is considered acceptable.
In some situations it may be necessary to recline a backrest and tilt a seat more than these recommended limits. This may result in some reduction in the performance of the belt restraint system, but it is sometimes a trade off that must be made for reasons of postural stability. In these situations, it is still desirable to keep the lap angle steep and the shoulder belt as close to the upper torso as possible, perhaps by adjusting the locations of the belt anchor points more rearward in the vehicle.
It is also important to clarify the difference between seat recline and tilt angles used in the WC19 frontal impact test, and the wheelchair design and user instruction requirements noted above. When a wheelchair is tested on an impact sled according to the requirements of WC19 as specified in Annex A, the seat tilt angle and back-support angle are usually set between 5 and 15 degrees to the horizontal and vertical, respectively. Wheelchair manufacturers know that these test angles are recorded in the test report. However, just because a wheelchair has been tested with the seat adjusted to an angle of 5 to 15 degrees does not mean that these are the maximum acceptable recline or tilt angles for use in transportation. While wheelchair manufacturers may recommend recline and tilt angles in this range, they should also indicate that recline and tilt angles up to 30 degrees are acceptable.
Finally, it should be noted that WC19 requires that tilt-in-space wheelchairs are dynamically tested at 30 mph with the seat tilted rearward of the most-forward tilt position. Thus, the tilt locking mechanism is dynamically loaded and must demonstrate that it will not fail catastrophically in a relatively severe frontal crash. Although the same principles about maximum tilt and recline angles apply to non-WC19-compliant wheelchairs, the fact that the tilt mechanism may not be strong enough to hold up under frontal crash loading adds an additional concern to using higher seat tilt angles, especially when the tiedown straps are attached to the wheelchair base rather than the seat. If the seat-tilt locking mechanism fails, a more reclined seat will pitch forward more than a more upright seat. A sudden and large change in seat orientation due to failure of a tilt locking mechanism would be likely to reduce the effectiveness of the belt restraint system, and further increase the possibility of the lap belt loading the abdomen of the wheelchair user.
C-14 What does WC19 say about head restraints, and what should I do for rear-impact protection?
At the present time, WC19 is silent on rear head restraints for wheelchair occupants, but this topic, along with wheelchair backrest performance in rear impacts, is currently being addressed in research and development projects, and will be included in a future update of, or addition to, WC19. The primary issue and concern is neck injury in rear impact crashes. While this is an important concern, it is not nearly as large a concern as injuries in frontal crashes, especially in larger school buses. In the meantime, the use of wheelchair seating systems that have high backrests and that include some kind of padded rear head support will offer enhanced occupant protection, both during rebound in frontal crashes and in rear impacts.
It should also be noted that the fact that the typical wheelchair back support is likely to deform somewhat during rear-impact loading is probably a positive factor in most rear impacts, since the forces on the neck are reduced when there is some deformation of the back support. In this regard, it is important not to install a vehicle-anchored head support system without including additional vehicle-anchored support for the wheelchair back support, since a strong rear head restraint without strong back support could result in injurious loading to the neck in a rear impact. The primary challenge in providing effective rear head and back support using a vehicle-mounted system is achieving close positioning of the support surfaces to the backrest of the wheelchair and head of the occupant. This is not easily accomplished when a wheelchair space in a vehicle is used by a wide range of wheelchair users with different types and sizes of wheelchairs.
C-15: Will I be denied access to transport vehicles if I do not have a WC19 compliant wheelchair?
No. It was never the intent that WC19 would be used to limit or restrict wheelchair user's access to motor-vehicle transportation, and this is specifically stated in the Foreword to the standard. Rather, the purpose of WC19 is to establish reasonable design and performance requirements for wheelchairs related to transportation safety so that wheelchair users have the opportunity to travel in motor vehicles with more safety than has previously been available. It would be ideal if all occupied wheelchairs in motor vehicles complied with WC19. However, even if manufacturers and consumers fully embrace the concept of the WC19-compliant wheelchair, it will be many years before the majority of wheelchairs are in compliance with WC19. Thus, it is going to be necessary to deal with non-WC19-compliant wheelchairs in transportation for the foreseeable future, and it is not appropriate or acceptable to limit access to transportation systems if a wheelchair user does not have a WC19 wheelchair.
Also, ADA specifically specifies that access to public transit vehicles cannot be denied to people using “common” wheelchairs and that they must be provided with wheelchair securement stations meeting specific size and securement strength requirements (see FAQ: Question A-10)
C-16 Can a non-WC19-compliant wheelchair be retrofitted to include the four securement points?
This is certainly possible and is allowed by WC19, at least with regard to retrofit attachment of four suitably strong securement points. However, since, for most wheelchairs, some modifications to the design of the wheelchair frame and/or materials is necessary to achieve the required dynamic strength, providing a retrofit kit of four bolt-on securement points will generally not be sufficient to comply with even the frontal-crash test requirements of WC19. Thus, while there is probably a safety advantage to adding easily accessible securement points to the strongest points on the frame of non-WC19-compliant wheelchairs, this will probably not result in complete compliance with WC19 and is therefore unlikely to be done for reasons of liability. At this time, only one wheelchair manufacturer is offering a retrofit kit to convert a wheelchair with securement points.
C-17 What if I want to secure my wheelchair by something other than a four-point, strap-type tiedown? Can this be crash tested?
While WC19 requires that a wheelchair provide for securement using a four-point, strap-type securement system for reasons of compatibility between "in-vehicle" securement systems and wheelchair securement points, a wheelchair can also be designed or modified for securement by other types of tiedown systems. RESNA WC-4_2012 Section 18 (WC18) does currently provide methods and performance criteria for testing commercial wheelchairs with other types of tiedowns, such as a dockign securement device (i.e., EZ Lock or QLK-150).
C-18: Is it OK if I make modifications to a WC19 wheelchair?
Because the structural design and strength of a WC19 wheelchair and its various load-carrying components are critical to its successful crashworthiness performance, modifications to any of the primary load carrying components, such as drilling of holes or replacement of parts, could compromise the crashworthiness of the wheelchair and should not be made without consulting the wheelchair manufacturer. Making modifications to non-structural parts of a WC19 wheelchair is less dangerous, but should be done with adherence to basic occupant-protection principles as much as possible. Thus, modifications that reduce the presence of sharp and rigid components or improve the retention of add-on components are encouraged.
C-19 What does WC19 say about auxiliary equipment on WC19-compliant wheelchairs, such as trays, oxygen tanks, and other add-on equipment that may be necessary for the particular wheelchair user?
The current version of WC19 does not directly address the design, performance, or securement of auxiliary or add-on equipment and devices, other than requiring batteries, motors, and other electrical components that are inherent parts of powered wheelchairs, or any other wheelchair component in excess of 100 g, to remain attached to the wheelchair during the 30-mph frontal crash test. However, the standard does address wheelchair add-on equipment indirectly by requiring the wheelchair manufacturer to provide warnings in its product literature that alert the consumer to:
- remove and secure auxiliary equipment separately in the vehicle whenever possible, or at least to
- secure auxiliary equipment to the wheelchair so that it will not break free and injure other occupants in a crash,
- use gel cell batteries on powered wheelchairs,
- and use soft or padded trays for situations when they cannot be removed from the wheelchair during transit.
Although users of WC19-compliant wheelchairs should contact the manufacturer with regard to making any significant changes to the basic structural components of the wheelchair or seat, it should not be necessary to consult the wheelchair manufacturer for dealing with the variety of add-on equipment during transit. Rather, it is simply important to realize that this equipment, and particularly heavier and rigid items, needs to be secured more effectively to the wheelchair than is typically done for daily use, and that it should be removed and secured elsewhere in the vehicle if possible. The strength of the device or mechanism needed to secure the item depends on the weight of the add-on component, but there are many types of tiedown straps and devices that should be suitable for most equipment. It is, of course, possible to test these devices by using them to secure add-on devices to the wheelchair during a 30-mph frontal impact test of the wheelchair, but the standard does not yet require this.
C-20: Can wheelchair scooters and stroller type wheelchairs comply with WC19?
WC19 does not exclude any type of wheelchair from complying with WC19 unless it does not allow for a seated posture. If a wheelchair provides for a seated posture and complies with all the other requirements of WC19, the wheelchair is considered a WC19-compliant wheelchair. This does not mean that all makes and models of wheelchairs can be easily modified or redesigned to comply with WC19 requirements. Some, such as three and four-wheel powered scooters, may require more significant changes in design than others. However, as previously noted, a wheelchair does not need to be particularly heavy and/or built like a tank to comply with the frontal-impact test of WC19. Some low-weight tilt-in-space stroller-type wheelchairs have successfully passed the crash test with relatively minor modifications to the non-WC19 compliant version of the wheelchair.
C-21 How do I secure wheelchairs that do not comply with WC19?
Usually with great difficulty and without a lot of confidence that the wheelchair will remain secured in transit, much less in a vehicle crash. The problem of finding adequate securement points on wheelchairs has become even more challenging over the past several years with a movement away from the standard welded tubular frame wheelchairs that usually provide two rear and two front securement points at the junctions of horizontal and vertical parts of the frame. Many heavy powered wheelchairs with their classy plastic frame and motor covers (sometimes called "shrouds") present special challenges. It is often impossible to find any suitable securement points, much less four such securement points, to which it is possible to attach tiedown hooks and/or straps.
With non-WC19-compliant wheelchairs, the concern for compromising the crashworthiness strength and integrity of the wheelchair frame structure is obviously not as real as it is with WC19 wheelchairs for which unauthorized changes could greatly reduce the dynamic strength of the wheelchair. Therefore, modifying the non-WC19-compliant wheelchair frame to provide some type of securement points is likely to improve the ability to effectively secure the wheelchair, especially when compared to having no suitable securement points. Even so, making such changes should be done with great care, with sound engineering guidance as to the materials used and knowledge of the potential forces involved in securing the wheelchair, which can exceed 3000 lb per securement point for heavy wheelchairs.
One approach to improving the ability to secure many non-WC19-compliant wheelchairs is to permanently attach looped straps at places on the wheelchair that are judged to have good strength but that are not easily accessible or attached to with conventional tiedown strap assembly end fittings. For example, the strap loops can be attached to structural members of power-based wheelchairs that are under the plastic housings, and the loops can be made to project through holes in plastic housings so that they are easily reached when the wheelchair is in a motor vehicle. Although the strength of a wheelchair and its attachment points is still in question if the wheelchair has not been crash tested, the use of these straps will usually offer easier and more effective wheelchair securement than what could be achieved without the straps. Most manufacturers of WTORS sell these add-on strap loops, including Safe Haven by New Haven Moving Equipment, Q'Straint, and Sure-Lok. (See the Ride Safe Brochure for phone numbers and websites of above manufacturers, as well as others).
In searching for the best solution to effectively securing non-WC19-compliant wheelchairs, it is recommended that a “team approach” be used, similar to that adopted by the Washtenaw Intermediate School District (WISD) in Ann Arbor, Michigan. This approach has been successfully used in dealing with difficult wheelchair situations. Their approach, and some specific guidelines on dealing with different types of wheelchairs during transportation of students with disabilities, are described in a 1995 document entitled School Bus Transportation of Students in Wheelchairs: A manual of Procedures and Practices Used by the WISD for Providing Effective Wheelchair Securement and Occupant Restraint. This can be purchased from WISD at P.O. Box 1406 Ann Arbor Michigan.
C-22: Do you have any general information on the RESNA WC19 standard that our organization could use in its monthly newsletter?
Yes, there is a news release prepared by the RESNA SOWHAT Subcommittee announcing the passage of the WC19 standard in April 2000. The following announcement is free for dissemination by any organization.
News Release: June 22, 2000
New Transit Wheelchair Standard-ANSI/RESNA WC19
A new national wheelchair standard that addresses the design and performance of wheelchairs when used as seats in motor vehicles has recently been approved by the American National Standards Institute (ANSI). The new standard is based on the fact that the most effective and common method for securing a wide range of wheelchair types and sizes in both public and private vehicles, is a four-point, strap-type tiedown system. Thus, one of the primary requirements of the new standard is that a wheelchair designed for occupancy in a motor vehicle be provided with four easily accessible tiedown points for facing-forward securement in a motor vehicle. The standard further requires that the wheelchair and securement points be dynamically crash tested at 30 mph with an appropriate size crash test dummy seated in the wheelchair. The wheelchair may also be designed to be secured by other more automatic tiedown methods, but it must provide for four-point securement to comply with the new standard.
In addition to addressing the dynamic strength and crashworthiness of wheelchairs, the new standard aims at improving the ease by which a wheelchair can be secured using a four-point tiedown system, by requiring that the four tiedown points be easily accessible using hook-type attachment hardware. Wheelchairs that comply with the standard will therefore not only make riding in a motor vehicle safer for the wheelchair user, but it will make it much easier and quicker for those involved in securing the wheelchairs in public transit vehicles.
While the primary goal of the standard is to reduce the potential for injury to wheelchair-seated occupants in the event of a vehicle impact, the standard also addresses wheelchair performance related to normal vehicle operating conditions. For example, the size and turning radius of a wheelchair may affect the ease of entering and exiting a motor vehicle, and maneuvering inside the vehicle into a forward-facing position at a designated tie-down station. Accordingly, the standard requires that information regarding a wheelchair's size and turning radius be provided in the manufacturer's presale literature. Additionally, a wheelchair's lateral stability can affect the comfort and security of the user during travel, so the standard requires measurement and disclosure of lateral movement in a wheelchair tilt test.
Of importance to the seating clinicians and wheelchair users is that by April 2002, all wheelchairs in compliance with WC19 shall provide for anchorage of a pelvic belt that meets specific location and strength requirements.
When development of the new standard began over four years ago, very few wheelchairs were designed with concern for occupancy and crashworthiness in motor vehicles. According to Dr. Schneider, many wheelchair companies, and all of the larger wheelchair manufacturers, are already designing and crash testing wheelchair models to the requirements of this new standard. He further notes that it is important to view the new standard in the totality of daily wheelchair functions and uses, and the range of other standards to which all wheelchairs should comply. Wheelchairs must first serve as effective mobility devices. Transportation is only one daily activity though it introduces additional unique circumstances and requirements for wheelchairs and wheelchair occupants.
C-23: What is the difference between RESNA WC19 and ISO 7176-19? If I comply with the requirements of one of these standards, do I comply with the other one?
The simple answer to this question is that compliance of a wheelchair with RESNA WC19 does not imply compliance with
ISO 7176-19, or vice versa. Although the
test procedures are similar, there are some key differences in performance
requirements and overall scopes of the standards. It is possible, however, for a wheelchair to
be compliant with both standards at the same time.
Before answering this question in greater detail, it should be emphasized that RESNA WC19 (WC19) and ISO 7176-19 were developed together and with significant coordination and correspondence between the Working Group of the RESNA Wheelchair Standards Committee known as the Committee on Wheelchairs and Transportation (COWHAT) and the Working Group 6 of ISO TC73 SC1. In fact, much of the leadership and authorship for the two standards came from the same individuals.
Although there was considerable exchange of information and discussion between the two standard-development groups, and every effort was made to harmonize the two standards during their nearly simultaneous developments, there are some differences in the two documents.
One primary difference in the method for conducting the frontal impact test is that WC19 specifies and, in fact, requires the use of a surrogate four-point strap-type tiedown to secure the wheelchair on the sled platform. By comparison, ISO 7176-19 requires that the wheelchair be secured by a four-point strap-type tiedown that complies with the frontal impact test of ISO 10542, which can be either a commercial tiedown or the surrogate tiedown.
Scope of Standards
The standards differ in scope in that ISO 7176-19 currently only applies to children and adults with a mass
of 22 kg (48 lb), while WC19 also applies to wheelchairs designed for children with
a body mass of 12 kg (26 lb, or approximately 3 years old) or more.
WC19 has several design requirements
that are not included in 7176-19. WC19 requires
that the wheelchair must be able to provide for a seated posture with a back support angle of 30 degrees or less to the vertical and a seat angle of 30 degrees
or less from the horizontal (e.g., a mobility device that allows only for very
recline postures does not comply). The mass of the unoccupied wheelchair, size
and turning radius, length and breadth are required to be measured and reported
in the presale literature.
WC19 also requires that wheelchairs
designed to accommodate children with body mass under 23 kg have a crashworthy 5-point harness, as well as a head and
back restraint with a back height of at least 555 mm (21.9 in). This is consistent with the protection
provided by and required for child restraint systems under Federal Motor
Vehicle Safety Standard 213.
Both standards include the same design requirement with regard to the type and number of wheelchair securement points, in that both standards require that the wheelchair provide at least four securement points for securement using a four-point, strap-type tiedown that comply with the same structural geometry specifications. However, the standards differ with regard to the opening geometry such that WC19 is more restrictive. In particular, the securement-point opening for WC19 must be 50-to-60 mm in length and 25 to 30 mm in width, whereas the opening required by 7176-19 must be greater than 60 mm in length and greater than 25 mm in width. Thus, an opening that is larger than 60 mm in length and/or larger than 30 mm in width would comply with 7176-19, but not with WC19. Likewise, an opening that is 50 mm in length would comply with WC19, but not with 7176-19.
The standards also specify that these securement points must be located within certain zones relative to each other and the ground. These zones are the same in the side view for the two standards but are different in the top view. WC19 currently allows the securement points of a
chair with a seating width of less than 400 mm to be less than 200 mm of each
other laterally, while 7176-19 doesn't allow the rear securement points to be
closer than 200 mm.
Wheelchair-Anchored Belt Restraints
There are two primary differences in the design requirements of the two standards with regard to occupant restraint. The first is that WC19 requires that a wheelchair provide the wheelchair occupant with the option of using a wheelchair-anchored lap belt and that a wheelchair-anchored lap belt be used instead of a vehicle-anchored lap belt in the frontal impact test. 7176-19 allows a wheelchair to provide for, and be crash tested with, a wheelchair-anchored lap belt, or even wheelchair-anchored lap and shoulder belts (as does WC19), but it does not require it. However, the design requirements for the wheelchair-anchored lap belt are the same in both standards.
The second difference between the
standards is that WC19 requires that a wheelchair designed for use for
occupants under 23 kg provide a wheelchair-anchored five-point harness in order
to provide smaller children with comparable protection as that achieved by a
child restraint system. This means that a wheelchair that is rated for
occupants from 15 kg to 50 kg must provide both a five-point harness and a
wheelchair-anchored pelvic belt. ISO 7176-19 does not include this
Both standards include performance requirements for wheelchairs for:
However, WC19 requires that the
wheelchair achieve a rating of at least “acceptable” with regard to the ease of
proper placement of vehicle-anchored three-point belts and to the extent to
which proper positioning and geometry of a three-point belt can be achieved. 7176-19 only requires that the rating for
accommodation of vehicle-anchored occupant restraint systems by reported in the
product presale literature.
- a 48-kph (30-mph) frontal-impact test,
- accessibility of securement points using a standard hook gauge, and
- a test for wheelchair accommodation of vehicle-anchored belt restraints.
Also, both standards include performance requirements for wheelchair-anchored belt restraints (when provided in 7176-19 and required by WC19) based on either ECE Reg. 16 or FMVSS 209 in 7176-19 and on FMVSS 209 in WC19.
WC19 stipulates several other performance requirements that are not included in 7176-19, including:
- a test for tiedown clear paths and proximity to sharp edges,
- a test for lateral stability (or really lateral movement), and
- a test for turning radius and turn-around width based on Section 5 of ANSI/RESNA wheelchair testing.
With the exception of the clear-path/sharp-edge test, these additional tests are disclosure requirements, not pass/fail requirements, in that the wheelchair manufacturer must disclose the test results in their presale literature.
Frontal Impact Test Methods
The primary and most important performance requirement of both standards is satisfactory performance in a 48-kph, 20-g frontal-impact test. As previously indicated, this test is conducted by securing the wheelchair on the sled platform using a surrogate four-point strap-type tiedown which his specified in the Annex D of WC19 (see the engineering drawings for all surrogate tiedown and occupant restraint system (SWTORS) components here). 7176-19 allows the test to be conducted using a commercial four-point strap-type tiedown that has been successfully tested to Annex A of ISO 10542. Since the surrogate four-point tiedown system of the SWTORS meets this requirement, it can be used to secure the wheelchair in 7176-19 testing. Thus, a frontal impact test conducted in WC19 with a 76-kg ATD is also conducted in accordance with 7176-19. However, a frontal impact test that is conducted using a commercial four-point tiedown is not conducted in accordance with WC19.
As mentioned previously, WC19
requires that a wheelchair-anchored lap belt be used instead of a
vehicle-anchored lap belt in the frontal impact test. 7176-19 allows a wheelchair to provide for,
and be crash tested with, a wheelchair-anchored lap belt, or even
wheelchair-anchored lap and shoulder belts (as does WC19), but it does not
Frontal Impact Performance Criteria
Section 5.3 of WC19 and Section 5.2 of 7176-19 specify the wheelchair performance criteria for the 48-kph frontal impact test of Annex A. As previously noted, the test methods are the same except for the allowance of a commercial four-point strap-type tiedown to secure the wheelchair in 7176-19 and the requirement to use a surrogate four-point, strap-type tiedown in WC19.
The primary difference between the performance
criteria of the two standards is that WC19 is worded so that only a “complete”
failure of the following components will fail the test, whereas ISO 7176-19
says that they shall not “show visible signs of failure”:
Therefore, even if all other
performance criteria are met, a hairline crack in a frame member can cause the
wheelchair to fail the frontal-impact test in 7176-19, but it will pass in
- primary load-carrying components,
- structural components of the wheelchair
- locking mechanisms of tilt seating systems, or
- webbing of the WTORS.
Other minor differences in the
performance requirements for the frontal impact test are below:
The net result is that the
performance criteria for the frontal-impact test in WC19 are generally greater
than those for 7176-19 and compliance with one standard does not imply
compliance with the other.
- WC19 specifies that rigid components, parts,
equipment or accessories in excess of 150 g shall not detached from the
wheelchair, while 7176-19 has a 100 g limit.
- WC19 requires that detachable seating systems
must not separate from the wheelchair base frame at any attachment points,
while 7176-19 is silent on this issue.
- WC19 requires that deformation of wheelchair
securement points cannot prevent disengagement of any tiedown hooks, while
7176-19 is silent on this issue aside from requiring that the release of the
wheelchair from the tiedown system shall not require the use of tools.
- 7176-19 requires that removal of the ATD from
the wheelchair after the test shall not require the use of tools (other than a
hoist), while WC19 is silent on this point.
- WC19 does not allow any securement hooks of
WTORS to detach from wheelchair securement points, or occupant belt restraints
to detach at anchorages, disconnect at buckles, or show complete webbing
failure during or after the test, while 7176-19 is silent on this.
- WC19 requires that the batteries and electronic
components of powered wheelchairs remain attached or tethered to the battery
compartment, while 7176-19 is silent on this.
While the key requirements and pass/fail criteria of RESNA WC19 and ISO 7176-19 are essentially the same, there are some differences in the scope of wheelchairs covered by the current standards, in the scope and level of design requirements, in the number of performance requirements, and in the test methods and pass/fail criteria for the frontal-impact test. The scope of WC19 current applies to
pediatric wheelchair for children aged three years and older, whereas 7176-19
applies only to children six years and older at this time. With one exception, the requirements and test
methods of WC19 are more demanding or more restrictive than for 7176-19. This exception is that only a “complete”
failure of a wheelchair or WTORS component will fail the performance
requirements of WC19, while a “visible sign of failure” of a component will
fail the 7176-19 criteria.
Group D. Questions: WC19-compliant Wheelchair Seating (ISO 16840-4; RESNA WC20)
D-1: What is the scope and requirements of the wheelchair seating standards (RESNA WC20 and ISO-16840-4)?
The primary focus of these standards
is to provide a means for evaluating the dynamic crashworthiness of after-market
wheelchair seating systems independent of testing the seating system on a wide
range of commercial wheelchair frames. The standards specify a surrogate
wheelchair frame (SWCF) to which the seating system can be attached and
dynamically tested on an impact sled in conditions that represent worst-case
loading conditions on a range of wheelchair frames. In addition, there is a test
method that allows the seating system to be rated with regard to allowing
proper placement and fit of vehicle-anchored belt restraints to the wheelchair
When a seating system is dynamically
tested on the SWCF in a 30-mph frontal sled test, the primary performance
criteria in WC20 and ISO-CD16840-4 standard are:
- that the seating system, including seat and
back support, offer effective vertical and horizontal support for the crash dummy
so that the dummy is in the wheelchair in a seated posture at the end of the
- that primary support components or structures do
not show visible signs of failure that prevent them from supporting the mass of
the ATD (ISO), or completely fail (WC20)
at the end of the test,
- that all seat and back support attachment hardware
remains attached to the wheelchair and seating system,
- that no parts of the seating system with a mass
greater than 100 g (ISO) or 150 g (WC20) break loose, and
- that there are no sharp edges on the seating
system after the test.
D-2: What is the difference between occupant-restraint belts and positioning or postural belts?
The term occupant-restraint system is taken from the field of automotive safety and is reserved for systems that are designed and intended to offer protection to the occupant of a motor vehicle in a crash. Few postural and positioning belts on wheelchairs have been designed to withstand the forces generated by an occupant in a frontal crash, which can exceed a 1500 lb force. Positioning belts should not be used as an occupant restraint in a motor vehicle. While WC19 and WC20 allow for positioning and postural belts on wheelchairs or seating systems to be crash tested and approved as occupant restraint belts, the types of anchorages and buckles typically used in these systems, such as sheet-metal screws through metal grommets and Velcro fasteners, are not acceptable in occupant restraint system design and would generally fail in the frontal-impact test. Such postural/positioning belts provided by the manufacturer of a wheelchair or seating system must therefore be labeled as "not for restraint in a motor vehicle."
NOTE: In WC18, WC19 and WC20 the term "belt" is used to refer to a length of webbing material in occupant restraint systems and the term "strap" is used to refer to a length of webbing material used in a wheelchair tiedown system.
D-3: Do postural and positioning belts present a hazard or injury risk if worn while a wheelchair-seated occupant is traveling in a motor vehicle?
Not really. Although positioning belts are often placed across the chest or abdomen and therefore will apply forces to the occupant at undesirable locations that could result in thoracic and abdominal injuries in a severe crash, it is difficult to find a situation where using these belts would be worse than not using them. For example, if a wheelchair user only uses wheelchair-anchored chest and/or lap belts, then this would be their only means of restraint in a crash situation. However, some type of restraint, even though incorrectly applied and limited in loading capacity, is probably better than no restraint at all. It will help reduce the extent of occupant movement and/or the speed of contacting the vehicle interior, and will thereby reduce the probability of injury from contact with vehicle components or other vehicle occupants and wheelchairs. On the other hand, if the wheelchair occupant also uses a vehicle-anchored restraint system with both upper- and lower-torso belts, then the wheelchair-anchored postural belts should not be a significant factor, either in offering occupant protection or in causing occupant injuries in a moderate or severe crash situation.
D-4: Is it safe to use other types of head-restraint and support devices when traveling in a motor vehicle?
If a wheelchair user's head is restrained from forward movement by some type of headband or head-restraint system that goes around the front of the head, there is concern that the torso may move forward more than the head in a frontal crash, and that this differential movement between the head and torso could result in injury to the neck. Also, it has been demonstrated in frontal impact tests with child crash dummies that neck collars used to provide head support can cause increased bending moments (a "moment" is a rotational force around an axis) at the upper neck if the collar is too stiff. This does not mean that head restraints and neck collars should never be used in transit, since head control for some wheelchair users may be more important to injury risk than is the concern for neck injury in a crash situation. However, it does mean that the head-restraint system should be designed to break away at relatively low levels of force so as to reduce the possibility of neck injury in a crash situation. In addition, soft neck collars should be used to minimize the increase in upper-neck bending moments that can cause injury to the upper cervical spine.
D-5: What if I need to use an after-market customized seating system that has not been crash tested?
WC19 currently evaluates a total wheelchair system, including the wheelchair frame or base and the wheelchair seat and backrest. This works well when the wheelchair manufacturer provides a complete wheelchair system, including both the base frame and seating system. However, in some cases (some suggest about 20% of wheelchairs), a specialized seating system from another wheelchair manufacturer, or an after-market seat manufacturer, is prescribed. In this case, it would be desirable to purchase only a WC19-compliant wheelchair base, rather than a complete wheelchair system from the wheelchair manufacturer. Concerns for liability have led legal departments of wheelchair companies to not allow the sale of WC19-compliant wheelchair bases (i.e., base frames with four crash-tested securement points) unless a seating system that has been crash tested on that base is sold with it. Such policies have led to the need for the consumer to purchase a wheelchair seat from the wheelchair manufacturer in order to obtain a transit option wheelchair, and then to replace that seat with the desired customized seating system. This is an expensive approach for the consumer and therefore far from ideal.
This problem has been resolved somewhat by wheelchair companies working together with manufacturers of after-market seating systems to develop and co-sponsor crash tests using various combinations of wheelchair bases and seating systems. These cooperative efforts have led to policies in which the wheelchair manufacturer will sell a wheelchair frame with the transit option if the after-market seating system is known to them and has been included in these crash tests.
In 2001, one of the major wheelchair companies has taken a more enlightened approach to resolving this problem by adopting the policy of selling wheelchair bases with the transit option, even when the seating system is unknown. The product literature appropriately states that the wheelchair manufacturer is notresponsible for the performance of the seating system, and that the use of seating systems that have not been successfully tested to WC19 may place the wheelchair user at increased risk of injury while in transit, or words to that effect. Hopefully, other wheelchair manufacturers will begin to see this policy as being in the best interest of the wheelchair user’s safety and will adopt a similar approach.
E. Acronyms and Abbreviations
- ADA - Americans with Disabilities Act
- ANSI - American National Standards Institute
- AT - Assistive Technology
- ATBCB - Architectural and Transportation Barriers Compliance Board
- ATD - Anthropomorphic Test Device (Dummy)
- ATP - Assistive Technology Practitioner
- ATS - Assistive Technology Supplier
- CAT - Center for Assistive Technology
- CDC - Centers for Disease Control
- CMU - Carnegie-Mellon University
- COWHAT - Committee on Wheelchairs and Transportation, a RESNA standards group (formerly called the Subcommittee on Wheelchairs and Transportation or SOWHAT)
- CP - Cerebral Palsy
- CPSC - Consumer Product Safety Commission
- CSA - Canadian Standards Association
- CVS - Crash victim simulation
- DOT - Department of Transportation
- DOJ - Department of Justice
- D&U - Dissemination and Utilization
- FEA - Finite Elements Analysis
- FMVSS - Federal Motor Vehicle Safety Standards
- GR - General Requirement
- IEEE - International Electrical and Electronic Engineering Society
- IRB - Institutional Review Board
- IRAP - Injury Risk Assessment and Prevention Laboratory
- ISO - International Standards Organization
- J2249 SAE - Society for Automotive Engineering Standard for Wheelchair Tiedowns and Occupant Restraint Systems for use in Motor Vehicles
- Load - the force applied to the wheelchair and/or passenger as a result of the change in velocity
- MS - Multiple Sclerosis
- NCDDR - National Center for the Dissemination of Disability Research
- NCSA - National Center for Statistics and Analysis
- NEISS - National Electronic Injury Surveillance System
- NHSTA - National Highway Safety Transportation Administration
- NIDRR - National Institute on Disability and Rehabilitation Research
- NIH - National Institutes of Health
- OEM - Original Equipment Manufacturer
- OTR - Occupational Therapist, Registered
- OVR - Office of Vocational Rehabilitation
- Pitt or U-Pitt - The University of Pittsburgh
- PVA - Paralyzed Veterans of America
- R&D - Research and Development
- RERC - Rehabilitation Engineering Research Center
- RERC WTS - RERC on Wheelchair Transportation Safety
- RESNA - The Rehabilitation Engineering and Assistive Technology Society of North America
- SAE - Society of Automotive Engineers
- SOWHAT - Subcommittee on Wheelchairs and Transportation, a RESNA standards group (now called the Committee on Wheelchairs and Transportation or COWHAT).
- SWC - Surrogate Wheelchair
- SWCF - Surrogate Wheelchair Frame
- SWTORS - Surrogate Wheelchair Tiedown and Occupant Restraint Systems
- UMTRI - University of Michigan Transportation Research Institute