Abstract: A gravity operated emergency system for a multi-story building is disclosed including an elongate track having a central rack which is disposed along an outside wall of the building. A traveller is provided which moves along the track and has a pinion which rotatably engages the rack. A pair of bearing members engage opposite sides of the track and these bearing members are pivotally attached to the traveller so that as the pinion is brought into contact with the rack the bearing members clear the respective sides of the track and when the pinion is fully engaged in the rack the bearing members are resiliently urged into contact with an inside face of the track. A velocity control mechanism is provided to control the rotational speed of the pinion in the rack, and hence the speed of the traveller relative to the track. During an emergency, the user is received in a harness which is connected to the traveller and the traveller slowly lowers the user to safety along the track.