ISO 16840-4:2009 specifies test methods and requirements for design and performance, for instructions and warnings and for product marking and labelling of seating systems intended to be used as a forward-facing seat in a motor vehicle when fitted to a manual or powered wheelchair. It evaluates the frontal crashworthiness performance of complete seating systems for occupancy by adults or children of mass equal to or greater than 22 kg.

ISO 16840-4:2009 only applies to complete wheelchair seating systems including attachment hardware, designed to be used with a wheelchair base tested as part of a wheelchair system that conforms to ISO 7176-19 performance requirements and that has securement points for use with four-point, strap-type tiedowns.

ISO 16840-4:2009 applies to seating systems designed to be used with occupant restraints that anchor either to the vehicle, the tiedown system, the seating system or the wheelchair base.