What should I do if I use a very heavy wheelchair that may generate forces that exceed the strength capacity of existing tiedown devices in a severe crash?
The question of when to use extra tiedown straps is up to the wheelchair user and the transit provider, and depends on a number of factors. The answer also depends on whether the wheelchair complies with a transport standard WC19. For heavy wheelchairs that do NOT comply with the WC19 standard, the more straps the better. However, finding four or more suitable securement points can be difficult on many wheelchairs, and unless it is a WC19 wheelchair, none of these additional securement points have been dynamically tested.
The need for additional straps also depends on the type of vehicle and transit mode. For large city buses and large school buses, more than four straps is probably not needed, especially for WC19 wheelchairs, since this type of vehicle is very unlikely to ever experience a 30-mph crash to which the WC18-compliant tiedown straps have been tested.
Another factor is whether the occupant is restrained by integrated belts that anchor to the wheelchair or independent restraints belts that anchor directly to the vehicle. Adding extra tiedowns may be a good idea with integrated belts where the tiedowns are loaded by the combination of the heavy wheelchair and occupant.
For a WC19 compliant wheelchair, the standard allows wheelchairs that weigh more than 275 lbs. to provide for more than four securement points (e.g., 3 or 4 in the back). It also requires that the manufacturer’s presale literature indicate the number of securement points and tiedown straps used in the frontal impact test, if the number is greater than the minimum of four. However, wheelchairs weighing less than 275 lb must pass the WC19 test with only four securement points, and that wheelchairs weighing more than 275 lbs don’t have to provide more than four securement points.