The purpose of this study was to quantify landing forces experienced during various tractor and trailer exit methods ranging from making optimal use of hand rails and steps to jumping. The study investigated landing forces sustained by ten male subjects while exiting two tractors and a box trailer. Steps were retrofitted onto the back of the box trailer in order to show reductions in landing forces achievable from trailers that are retrofitted with improved access systems. The results showed squat jumping down from the back of a box trailer generated landing forces as high as 11 times body weight. However, using the trailer's retrofitted step and grab system while exiting resulted in landing forces reduced by over 66%. Jumping from the cab-level of a cab-over-engine (COE) tractor resulted in landing forces as high as 12 times the subject's body weight, whereas fully utilising the existing steps and grab rails kept the landing forces under two times their body weight. An approach that emphasises optimal entry/exit aids design based on human factors engineering, coupled with driver training is expected to minimise vehicle-related musculoskeletal injuries.
Abstract