Use of a modified HYBRID III 50th dummy to estimate the efficiency of market restraint systems for forklift truck drivers.

This study concerns the development of an experimental method intended to estimate the efficiency of restraint systems designed to protect forklift truck drivers. Human beings were not considered for use in these tests as the conditions of the latter were judged to be too dangerous. Since it is currently not possible to procure a dummy on the market capable of simulating the kinematics of a human being under lateral tip-over conditions of, the decision was taken to purchase a HYBRID III automobile crash-test dummy that we modified and adapted for our purposes. Observations and measurements previously performed on human subjects placed in situations of partial lateral tip-over were used in order to make modifications to the dummy and validate its performance.
Five cab configurations based on different restraint systems were used to restrain the subjects and the dummy to varying degrees so that the validation conditions were as varied as possible. The validation showed that the modified dummy could replace a human subject when the tests required only the simulation of their kinematics, including when a restraint system was on their trajectory.
The dummy was used on a second more realistic test bench to simulate the conditions of a full 90° lateral tip-over in a curve in order to estimate the efficiency of market restraint systems. Twelve configurations were tested and the effect of the assembly height of certain door-bar systems on the risk of ejection was also studied.
The results show that the door-bar systems that blocked the lateral face of the cab most, i.e. a door partially blocking the lateral space, and safety belt, kept the dummy inside the cab and thus would considerably increase the driver’s chances of survival in the case of tip-over. However, other poorly dimensioned equipment may not block the dummy’s movement or break, failing to ensure that the driver will remain inside the cab if it tips over. The severity of impacts to the head was evaluated when the head struck the roof and or one of the metal uprights of the cab frame or in the case of impact with the ground. Calculation of the Head Injury Criteria (HIC) showed that they were lower than the threshold of 560 set in our approach for impacts inside the cab, but that these exceeded 3400 in the case of impact with ground.