WC20: Seating Systems

ANSI/RESNA WC-4:2017, Section 20 - 
Wheelchair Seating Systems for Use in Motor Vehicles

WC20 is was first published in 2012 was an adaptation from the draft ISO 16840-4 standard.  The updated WC20 standard was published in December 2017 as part of the American National Standards Institute/ Rehabilitation Engineering and Assistive Technology Society of North America (ANSI/RESNA) Wheelchair Standards/ Volume 4: Wheelchairs and TransportationThe standard is available for purchase at the RESNA American National Standards webpage or by contacting RESNA:

RESNA, 1700 N. Moore St, Suite 1540, Arlington, VA 22201-1903
Phone: 703-524-6686 Fax: 703-524-6630 TTY: 703-524-6639
E-mail: info@resna.org

Seating systems that comply with WC20 are labeled with the symbol below.

To download a high resolution version of the Volume 4 Wheelchair Transportation Safety symbol click here:

            -   WC20 WTS Symbol-Vol4.png

            -   WC20 WTS Symbol-Vol4.pdf

            -   WC20 WTS Symbol-Vol4.jpg

Rationale for WC20

For many people with mobility-related disabilities who must remain seated in their wheelchairs when traveling in motor vehicles, their wheelchair must serve as the vehicle seat and therefore becomes an important part of the occupant-protection system. In these situations, wheelchairs must provide stable and effective support for their occupants during normal vehicle operation, emergency vehicle maneuvers, and crash conditions. Providing effective occupant support during crash conditions is especially important for maintaining proper positioning of the lap-belt restraint over the occupant’s bony pelvis during impact loading, thereby reducing the likelihood of the occupant “submarining” under the pelvic belt, which can result in injuries to the abdomen and spine from lap-belt loading. Wheelchair frames and seating systems that are not designed to withstand crash forces place their occupants at increased risk of serious injuries in vehicle crashes.

WC19 defines requirements for wheelchairs, including their seating systems, which are intended for use as motor vehicle seats. However, seating systems are often provided as after-market products, independent of a wheelchair frame and the same seating system may be adapted to more than one wheelchair frame. Therefore, requirements must be defined for seating systems alone, independent of a specific wheelchair frame. Such requirements are defined in WC20.

WC20 establishes design and performance requirements and related test methods to evaluate wheelchair seating systems relative to their use as seats in motor vehicles independent of their installation on production wheelchair frames. It accomplishes this by installing and testing the seating system on a surrogate wheelchair frame (SWCF) shown above that has been designed and validated to perform during a simulated 48 kph (30 mph) frontal crash in a manner that is representative of typical production wheelchair frames, and so that dynamic loading by an anthropomorphic test device (ATD), or crash-test dummy, representing the wheelchair occupant, produces nominally worst-case loading conditions on the seating system. The SWCF on which the seating system is installed can accommodate a wide range of types and sizes of production seating systems (see detailed engineering drawings for the SWCF here).

All types of seating systems, including specialized seating systems, are included in this standard. For the purposes of WC20, a complete seating system consists of a seat, back support and associated attachment hardware. The seating system may, or may not include postural support devices. The current version of WC 20 includes seating systems that may incorporate pelvic belt anchorages on the seating system, but does not include seating systems with shoulder/upper torso belts anchored to the seating system at this time.

Seating systems that comply with WC20 are intended for use only with wheelchair frames that are equipped with securement points specified in WC19, and that have been successfully crash tested using the methods described in Annex A of WC19. It is anticipated that future sections of ANSI/RESNA WC-4, or addendums to this section of WC-4, will address individual components of seating systems and seating systems with seat-integrated frames that are separate from the wheelchair base frame. WC20 also includes a test for the seating system’s accommodation of vehicle-anchored occupant restraints. Since occupant restraint positioning is key to effective protection, seating systems will be evaluated and rated based upon their level of accommodation of vehicle-anchored occupant restraints.

Scope of the Standard

WC20 establishes design requirements, performance requirements, associated test methods, and requirements for product labeling and manufacturer literature, for complete wheelchair seating systems consisting of a seat, a back support, and attachment hardware, but without a separate seating-system frame that connects to a wheelchair base frame.  It applies to seating systems intended for installation on manual and power wheelchair frames that include securement points and pelvic belt-restraint anchor points as required by WC19. It applies to seating systems intended for use by adults and children with a total body mass over 23 kg (51 lb, or approximately 6 years of age) who are transported facing forward in their wheelchairs in all types of motor vehicles.