While many wheelchairs are produced as a single piece of equipment made by one manufacturer, for others, a wheelchair base from one manufacturer can be paired with different styles of seating systems made by another company to better accommodate the specific needs of the person using the wheelchair. WC20 was developed to allow evaluation of the crash performance of different seating systems independent of the wheelchair frame. Seating systems consist of a seat, back support, and attachment hardware. Part 1 of the standard defines the scope, Part 2 incorporates other references, and Part 3 defines terminology.

Part 4 describes design requirements related to sharp edges and accommodating vehicle-anchored belt restraints. Part 5 describes performance requirements, which are essentially the same as those required in WC19 for frontal crashworthiness and accommodation of vehicle-mounted belt restraints. However, testing of wheelchair seating systems is performed using a Surrogate Wheelchair Base (SWCB) defined in Annex B. The SWCB allows evaluation of different styles of seating systems independently, and allows lateral adjustability to accommodate smaller and larger wheelchair seating systems.

Parts 6 and 7 describe requirements for written materials and documentation similar to those found in WC19. In WC20, Annex A describes frontal-impact test procedures, Annex B specifies the SWCB fixture, Annex C contains method for evaluating accommodation of belt restraints, and Annex D contains methods for performing quasi-static tests of wheelchair seating systems (which are recommended before performing dynamic testing but are not required.) Annex E provides sources for relevant information.