A long, heavy, metal gate swung from a tall pole by a cable that went from one end of the gate up over the top of the pole and down to the other end of the gate. When the gate was opened (rotated about the pole) it would simultaneously open two lanes, one on each side of the pole, and then when the gate was released, the weight of the gate caused the cable to unwind and close the gate. This ensured that the gate was always closed after being used. Later, when automobiles began using such gates, it was observed that a closed gate could be hit by the car bumper and swing open long enough for the car to get through.
