Complex sentence: The device they use is called "Aqua-Track" which, while attached to a moving rail car, sprays water at a pressure of 10,000 pounds per square inch directly onto the part of the rail where the leaves cling.
Split into simpler sentences: The device they use is called "Aqua-Track" which. Attached to a moving rail car, it sprays water at a pressure of 10,000 pounds per square inch directly onto the part of the rail where the leaves cling.