Human arm operation in driving motion can be classified into the two categories of steering wheel and gear stick manipulation. In this study, the operational characteristics of a human-steering system were experimentally analyzed in consideration of the mechanical properties of the human arm and related effects on muscle activity. The results highlighted three points in particular: (1) positioning to facilitate operation as well as the operational direction of the steering column angle and fore-and-aft positions can be determined on the basis of force manipulability in consideration of human joint-torque characteristics; (2) subjects feel that handling is easier when arm muscle activity is low during steering wheel operation; and (3) arm positioning and body pressure distribution have a very significant effect on arm muscle loads. Comprehensive consideration of these results is expected to be useful in the design of human-vehicle steering wheel systems.