Automatic gates are an important part of many active highway grade crossing warning systems. Their primary purpose is to provide a physical barrier that prevents vehicles and pedestrians from entering the crossing when a train is approaching or occupying the tracks.
The gate mechanism is the electromechanical system responsible for lowering and raising the gate arm. These mechanisms are designed for reliable operation in many different weather conditions and must withstand constant use over long periods of time.
Most gate mechanisms contain several major components, including an electric motor, a gear reduction unit, and a linkage system. These components work together to convert the motor's rotary motion into the controlled vertical movement of the gate arm.
The operation of the gate mechanism is controlled by the highway grade crossing controller. When train detection equipment senses an approaching train, the controller sends a signal to lower the gate arm.
After the train clears the crossing, the controller reverses the motor and raises the gate arm to allow roadway traffic to continue moving safely across the tracks.
Safety is a major concern in gate mechanism design. Many systems include obstruction detection that can stop or reverse the gate if it encounters an object during lowering. Breakaway mechanisms allow the gate arm to detach during vehicle impact to reduce damage and improve safety.
Some gate mechanisms also include manual override features that allow railroad personnel to manually raise or lower the gate during power failures or equipment malfunctions.