Accidents involving electric wheelchairs in Japan have increased as the nation's population ages. About half of all accidents are caused when the chair tips over sideways or backwards on a sidewalk. The authors have developed two kinds of safe technology intending to prevent such accidents. The first prevents the wheelchair from falling sideways on a sidewalk when the wheelchair is moving across the slope of a sidewalk. On a slope, the wheelchair easily swerves from the desired direction and goes down the slope because of gravity. The second measure prevents a large backward tipping angle when the wheelchair is moving up over grade height differences and slopes. The authors have configured a wheelchair which has a posture sensor, magnetic brake bar and small control board. Results of indoor experiments on not only simulated slopes and grade height differences but also in real outdoor environments have confirmed the effectiveness of the authors' support technology.