A downed power line is any high-voltage electrical cable that has fallen from its support structure (pole or tower) and landed on the ground, a vehicle, a fence, or a tree. Even if it is not sparking or making a sound, you should always assume it is live and extremely dangerous. The primary danger comes from the high voltage, which can cause severe injury or death. Electricity from a downed line can also energize the surrounding area, creating a lethal hazard known as "step potential" where the ground itself is electrified.