Should wheelchair manufacturers set special limits on the weight of occupants who can use WC19 wheelchairs?
WC19 specifies that the size and weight of the crash dummy used in the 30-mph frontal impact test be representative of the size and mass of the largest person for which the wheelchair is designed. Thus, if a wheelchair is designed only for use by children, then either the three-year-old (36 lb), six-year old (47 lb), or ten-year-old (80 lb) crash dummy or the 100-lb, small-adult, crash dummy would be recommended for use in the sled impact test. For wheelchairs designed for use by adults, there are small, midsize and large dummies used for testing, depending on the occupant mass limits of the wheelchair.
However, some wheelchair manufacturers note in their literature that wheelchair users who weigh more than the crash dummy used in the test should not use a particular WC19-compliant wheelchair. Given that vehicle manufacturers do not limit sale and use of their vehicles to people who weigh more than the 170 lb crash dummies used in federal motor-vehicle safety testing, it would be equitable if wheelchair manufacturers did not restrict use of WC19 wheelchairs to users who weigh less than the dummy used in the test.
Because the majority of crashes are less severe than a 30 mph delta V, WC19-compliant wheelchairs are likely strong enough to remain intact during most crashes even with heavier occupants. Product standards usually require designing for, and testing to, a set of reasonable, but somewhat worst-case conditions that may be experienced in the real world. It is rare that a standard requires products to be tested at the absolute extreme conditions of potential real-world exposure, especially when the likelihood of that exposure is very remote, as is the case with very high-severity motor-vehicle crashes. A 170-lb crash dummy represents about a 50th percentile adult by height and weight, and the 225-lb crash dummy represents a 95th percentile male by weight or about a 97.5 percentile adult by weight. Similarly, a 30-mph frontal crash test represents about a 95th percentile frontal crash pulse for a passenger-size vehicle, such as a van or minivan, and a much higher percentile for larger vehicles. In the real world, people who ride in vehicles are exposed to a wide range of conditions and circumstances that can increase the risk of injury beyond that covered by safety testing. Impact severities can be greater than 30 mph and they can come from different directions. Older occupants are at higher risk of injury than younger occupants. Heavier occupants are at greater risk than lighter-weight occupants. People in smaller vehicles traveling at higher speeds are at greater risk of injury in a crash than people in larger vehicles and/or vehicles traveling at slower speeds. A standard cannot, and does not, provide everyone with the same risk of injury in a crash.