WC18 applies to wheelchair tiedown and occupant restraint systems (WTORS), consisting of a system or device for securing wheelchairs, and a system of belts for restraining occupants seated in wheelchairs. This includes both strap-type and docking-type securement systems. The standard is focused on the application of WTORS to passenger vehicles so assumes a more severe crash environment. Part 2 references other RESNA standards and federal motor vehicle safety standards; definitions are included in Part 3.
Part 4 of WC18 defines design requirements. They define what elements comprise a complete WTORS system, requirements for wheelchair tiedowns and securement devices, specifications for wheelchair tiedowns/securement adaptors, and features and relevant federal compliance requirements for occupant restraint components.
Part 5 lists performance requirements. WTORS must meet flammability requirements of FMVSS 302, as well as most requirements of FMVSS 209. If the WTORS has a lap-shoulder belt component, crashworthiness in frontal impact is assessed in two tests, one with the lap-shoulder belt anchored to the vehicle, and one that uses the surrogate lap-shoulder belt with a wheelchair-anchored lap belt defined in Annex D of WC19. Options for testing with different combinations of belt restraints are also included. Tests are conducted either with a specific wheelchair model (SWM) or with a surrogate wheelchair defined in Annex E. Sled test procedures use a 48 km/hr (30 mi/hr), 20 g acceleration pulse, similar to that used in FMVSS No. 213 for frontal impact testing, although the allowable corridor is wider than the FMVSS No. 213 pulse. Details regarding the test buck, instrumentation, ATD positioning, wheelchair preparation, pre and post-test measurements, and reporting requirements are also included in Annex A. To pass the test, the system must meet wheelchair, head, and knee excursion limits specified for the ATD used in the test. Values are provided for 3YO, 6YO, 10YO, 5th female, 50th male, and 95th male ATDs. In addition, the ATD must be seated in an upright position after the test, the WTORS components should not completely fail, and the wheelchair should remain undamaged if a SWM is used in the test.
WTORS performance requirements also include geometric and adjustability specifications that are evaluated using procedures in Annex B. Annex C includes procedures for assessing the performance of WTORS under partially engaged conditions. WTORS must have less than 25 mm (1 in) of slip when tested under conditions described in Annex D. WC18 has requirements regarding written materials, including product identification and labeling, instructions for installers, advice and warnings for installers, user and maintenance instructions and warnings, in-vehicle placards, and instructions for WTORS components and subassemblies sold separately. The last Part provides direction on how to document compliance with the standard. In addition to the annexes that describe test procedures, Annex F provides design and performance recommendations.