Model are used to understand human factor as a framework around which human factor issues can be structured. SHEL(L),PEAR, Dirty Dozen S - Software H - Hardware L - Liveware E - Environment Liveware is at the center of the model, is the most critical and flexible component in the working Environment and subject to considerable variations in performance and suffer many limitations. Physical size and shape. In the design of workplace and equipment, body measurements and movements is considerd , which may vary according to factors such as age, ethnicity and gender. Human Factors inputs is provided in the design process, and data for these inputs are available from anthropometry, biomechanics and k...