What are the main safety concerns for someone seated in a wheelchair while in a motor vehicle?
In regular passenger cars, the vehicle seats are firmly anchored to the vehicle floor. They have no sharp edges, and are dynamically tested to provide support for the occupant. During a crash, a properly worn lap+shoulder belt keeps the occupant from injurious contact by holding the occupant in place and applying the restraint forces to the strong parts of the skeleton. The seat and belts prevent occupant ejection and minimize the potential for injurious occupant contact with the vehicle interior. Current vehicles also have airbags which provide supplemental protection in front and side impacts. All components of the occupant protection system, together with the vehicle’s structure, form a safety system that allows the occupant to “ride-down” or gradually absorb the vehicle deceleration.
In contrast, most wheelchairs have not been designed for use as seats in motor vehicles. The wheelchair frames and seats are generally not strong enough to withstand the thousands of pounds of impact forces that can result under crash conditions. For many wheelchairs, it is hard to find good places on the wheelchair frame to attach wheelchair tiedowns. Even when it is possible to find usable attachment points, they may not be strong enough to hold up under a serious crash. Instead, tiedown straps are often attached to the most accessible places on the wheelchair, which are often the weakest places. For example, if tiedown straps are attached to detachable footrests or armrests, the wheelchair will not withstand even a relatively minor crash event. If the wheelchair is not effectively secured, the mass of the wheelchair, which can exceed 250 lb, will add to the belt-restraint forces on the occupant’s body in a crash situation. In addition, for effective occupant protection, belt restraints must fit snugly over the pelvis and shoulders. However, the design of many wheelchairs often prevents a good fit of the lap+shoulder belt. Because of these differences, best practice is for a wheelchair user to transfer to the vehicle seat when possible.
Injury biomechanics research and crash investigation data show that position of the occupant relative to the impact direction also has significant safety implications. A forward-facing position is recommended for most travel situations. While not recommended, sometimes occupants in wheelchairs are placed facing sideways in the vehicle, since this makes entering and exiting easier. However, this is the least-safe orientation for frontal crashes that are the most common cause of injury. While a closely placed padded structure can provide effective frontal impact protection for occupants who face rearward, this option is generally limited to large buses. Accessories that are not needed during the trip should be stowed or secured during travel.