Research

Investigating the potential benefits of load limiters within the occupant restraint system for people travelling in wheelchairs (2016)

Paul Dryer, Rehabilitation Engineering Division, Kings College Hospital, London

On occasions when it is not feasible for wheelchair users to transfer to a vehicle seat (or child safety seat) it is necessary for people to remain in their wheelchair seat when travelling in a vehicle. The safety of people traveling in these circumstances is paramount when considering the combination of wheelchair, postural support system, vehicle design, wheelchair tie-down and occupant restraint system (i.e. the vehicle seat belt).

Seat belt load limiters are devices designed to allow the belt to ‘give’ when forces on the belt rise above a predetermined level. The seat belt is allowed to spool out of the retractor in a controlled manner, maintaining a constant restraining force as it absorbs energy. Seat belt load limiters have been widely adopted in many passenger vehicles, including wheelchair accessible vehicles (WAVs). Laboratory tests and field studies have shown that load limiting seat belts have the potential to reduce the risk of belt induced thoracic and neck injury for passengers seated in standard vehicle seats without supplementary restraint such as an airbag. These devices may bring about an increase in the forward movement (or excursion) of the occupant as they ‘ride-down’ deceleration forces.

The objective of this project is to investigate the relationship between peak seat belt force, occupant head excursion, and injury risk for people using their wheelchairs as an occupied seat in a motor vehicle. ISO 10542 sled tests will be undertaken using instrumented anthropometric test devices (ATDs) with and without the inclusion of load limiters within the occupant restraint systems. Test results will be interpreted by the project team, ensuring that test data can be related to real world scenarios. Knowledge gained through this study will be communicated to the PMG membership and beyond to inform risk management processes when making recommendations as to the safest way for wheelchair users to travel, and the risks and/or potential benefits of the inclusion of load limiters. Results will also be used to influence amendments to the Standard ISO 10542-1 ‘Wheelchair Tie-downs and Occupant Restraint Systems’ in order to facilitate improved general transport safety for wheelchair seated passengers in road vehicles.

Sled tests and associated equipment will be funded by industry project partners.

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