IRC's calculation method took into consideration 9,140 personal injury protection (PIP) claims closed in 2007. The cars in these incidents were divided into four weight groups. The IRC found that claims from the lightest group were 14.3 percent more expensive than from the heaviest vehicles. They also found that while 38 percent of the lightweight cars could resume commuting to work after the accident, 46 percent of the heavyweight vehicles were able to continue driving. Not only that, IRC's study says that driving a lighter vehicle made you 12 percent more likely to require hospitalization in case of an accident.