A motorized wheel chair is equipped with a safety system for bringing the wheel chair to a stop if a wheel chair user should experience an emergency situation which renders the user unable to safely control the wheel chair while in use. The safety system utilizes at least one switch mounted to an upright backrest for sensing whether or not the user's back is in contact with the backrest. If the user's back is in contact with the backrest, the wheel chair is operative and may be controlled in a normal manner. If the user's back moves out of contact with the backrest, whether voluntarily or because of an emergency situation, the safety system operates to disable operation of motors which operably propel drive wheels of the wheel chair, thus causing the wheel chair to be inoperative and bringing the wheel chair to a stop if in motion.