The Safety Net
Clinical Resources in Wheelchair Transportation Safety
For persons who need extensive mobility supports, the fields of rehabilitation, engineering, and transportation have made many contributions. The development of standards for safe transportation for people who use wheelchairs, including those requiring specialized seating systems, is just one of many collaborative initiatives being pursued by engineering, rehabilitation, and research organizations. One such initiative focuses specifically on wheelchair transportation safety.
Sponsored by the National Institute on Disability and Rehabilitation Research, The University of Pittsburgh and The University of Michigan Transportation Research Institute have joined in a partnership to establish the Rehabilitation Engineering Research Center (RERC) on Wheelchair Transportation Safety. The primary goal of the RERC is “to improve the safety of wheelchair users who remain seated in their wheelchairs while using public and private motor-vehicles”.
The RERC has published a report of their project activities, including a section on Frequently Asked Questions (FAQ’s), on their website: www.RERCwts.pitt.edu. At this website, physical therapists, occupational therapists, physicians, mobility device fabrication specialists, and other clinicians can find information on the following:
The following excerpts from the project’s FAQ’s represent the clinical nature of this resource.
Please note: Reference to any specific product, process, service, or manufacturer does not constitute endorsement or recommendation by either DDS or The Columbus Organization.
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?
Answer: 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?
Answer: 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.
C-1: What is WC-19 and what is its purpose?
Answer: There are many ANSI/RESNA* standards that address different issues of wheelchair design and performance. 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. WC-19, or more correctly, Section 19 ANSI/RESNA WC/Volume 1: Wheelchairs for Use in Motor Vehicles is the first and, so far, only ANSI/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 purpose of the WC-19 standard is to establish minimum wheelchair design and performance requirements that will 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 WC-19 is often referred to as a WC-19 wheelchair, as a transit wheelchair, or as a wheelchair with the transit option.
*American National Standards Institute/Rehabilitation Engineering & Assistive Technology Society of North America
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?
Answer: First of all, it should be noted that WC-19 does not place any requirements on the backrest recline or seat tilt angles used to transport persons in wheelchairs. WC-19 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 WC-19 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, WC-19 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 WC-19.
WC-19 also requires manufacturers of transit wheelchairs 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 WC-19 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 WC-19 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 WC-19 as specified in Annex A, the seat tilt angle and backrest 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 WC-19 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-transit 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 tie down 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 user.
A-14: Where can I get more information about products that conform to the industry standards related to wheelchair transport safety?
Answer: For more information on the products from specific manufacturers, we suggest you contact your local supplier on the manufacturer directly. The * indicates that these manufacturers actively participated in the development of the standards.
A. Wheelchair Securement and Occupant Restraint Products
New Haven Equipment
Ortho Safe Systems
EZ Lock, Inc.
B. Transport Wheelchair Products
Pride Health Care
*Sunrise Medical HHG
Mulholland Positioning Systems, Inc.
C. Wheelchair Seating Products
*Adaptive Equipment Systems
For more information on safe transportation for people who use wheelchairs, contact the organizations listed below:
Rehabilitation Engineering & Assistive Technology Society of North American (RESNA)
Rehabilitation Engineering Research Center on Wheelchair Transportation Safety
National Institute on Disability and Rehabilitation Research (NIDRR)
National Highway Safety Transportation Administration (NFTSA)
American National Standards Institute (ANSI)
|Return To Article|