Complex sentence: The island supports the pivot point for the rotating structures; when in the open positions, the aqueduct and road bridge line up along the length of the island, allow ships to traverse along each side of the ship canal.
Split into simpler sentences: The island supports the pivot point for the rotating structures. When in the open positions, the aqueduct and road bridge line up along the length of the island, allowing ships to traverse along each side of the ship canal.