Glossary
Safety Device
A mechanical device mounted on the car frame that grips the guide rails to stop the car in a controlled manner when triggered by the governor, preventing free-fall in the event of rope failure or overspeed.
The safety device (often simply called "the safeties") is mounted on the car frame, one on each side, engaging the guide rails. When the governor detects an overspeed condition, it pulls a linkage that activates the safety device. The device uses wedge-shaped jaws or rollers that are forced against the guide rails, creating friction that decelerates and stops the car.
Two main types exist. Instantaneous safeties stop the car very quickly and are suitable for lower-speed elevators (under 0.75 m/s). Progressive safeties apply a controlled, increasing braking force that brings the car to a stop over a longer distance, reducing deceleration forces on passengers. Progressive safeties are required for elevators with rated speeds above 0.75 m/s. Safety devices are tested annually or semi-annually by running the car at reduced speed and tripping the governor to verify proper engagement.