Fork lift overturns and head injury

Phase I, Phase II, Caterpillar, Allis-Chalmers, Clark, Hyster, Toyota and Entwistle fork lift upset studies have been conducted with Hybrid II dummies, Side Impact Dummies, and stunt men. The investigations concluded that the dummy lacks the ability to brace itself, hold on, and does not have adequate biofidelity to represent the human in a fork lift upset. Crushing injuries and death typically occur when the operator is thrown or jumps from the overturning forklift and is pinned by the overhead guard or canopy. The dummy studies demonstrated a wide range of Head Injury Criteria (HIC) values that were not reproducible. Furthermore, other injury producing variables such as angular acceleration, angular velocity or induced brain stress were not investigated. The injury level of 1000 for the HIC for the mid-sized male, small female, and 6 year-old has been recommended by the National Highway Transportation Safety Administration (NHTSA). The fork lift studies showed that HIC values were typically lower when the dummy stayed within the fork lift. Stunt-man experiments demonstrated that humans can brace themselves and hold on to prevent ejection and injury if they are lap-belted and have either a winged seat or hip restraint. The winged seat and lap belt was adopted by Clark in 1983 and the lap belt and hip restraints by Hyster in 1986 even though field acceptance levels were low.