Deficiencies in ingress/egress systems on large trucks are responsible for a substantial number of injuries that occur when drivers slip or fall getting into or out of their vehicles. Current standards and guidelines for the steps and handholds that comprise these systems lack quantitative specificity in key areas, provide primarily component-level rather than system-level guidance, and do not take into account important changes in the characteristics of the driver population, including increased age, increased body weight, and an increasing number of female drivers. This project will develop quantitative design guidelines and assessment tools for truck driver ingress/egress systems through quantification of driver ingress/egress behavior in the field, a laboratory study using a vehicle mockup, and biomechanical analysis of ingress/egress motions. In an initial field investigation, drivers recruited will be videotaped getting in and out of their vehicles at a truck stop and the step and handhold geometry of a wide range of vehicles will be measured. A laboratory study will be conducted with 60 male and female drivers with a range of body dimensions and age. Test conditions will include variations in the number of steps and their locations, the number of handholds and their locations, and the overall height of the vehicle floor above the ground. Data will include whole-body motion capture using a passive-marker optical tracking system, forces and moments exerted on the ground, steps, handholds, and steering wheel, and subjective assessments of ingress/egress difficulty. Drivers will get into and out of the mockup using self-selected movement strategies and using specific strategies identified in the field data. The movement and reaction force/moment data will be analyzed using inverse dynamics to estimate joint torques and body accelerations to develop a biomechanical method to assess system safety. Better systems are expected to require less hand force, require less horizontal force on steps (i.e., require less friction), produce lower joint torques at the shoulder and hip, and result in lower accelerations of the body center of gravity. The assessment methods will be applied using a digital human figure model capable of representing a wide range of body size and shape to develop specific design guidelines for steps and handholds. The guidelines and assessment methods will be disseminated through publications, standards organizations, and a dedicated website.
