Human factors as for falls on stairs were experimentally analyzed to obtain fundamental data to evaluate dimensions of tread and rise in regard to safety on stairs. A devised apparatus to give abrupt accelerations to a human standing posture on stairs was applied. Remarkable distinction of human balancing ability on different dimensions of tread and rise could not be found both in a young group or in an aged group. And then, gait movements on stairs in relation to stumbling, mis-footing etc. were experimentally analyzed. Some accidental factors, foot contact angles with tread etc., were closely correlated to dimensions of tread and rise. Many basic considerations could be obtained from these experiments.
