Contact wire is generally built in zig-zag to reduce the wear on pantograph slide. When the train is running at a high speed, the contact wire has to face the extreme working environment such as vibration shock, temperature difference, environmental corrosion, mechanical friction, and arc ablation [48].

Tram and trolleybus overhead wires are intentionally hung in a "zig-zag" pattern (officially called stagger) to prevent uneven wear on the vehicle's pantograph. The pantograph is the metal arm on top of the tram that collects electricity from the wire. It has a flat, carbon-lined contact strip on top. If the wire were perfectly straight and centered, it would eventually wear a deep, narrow groove into the center of the carbon strip, leading to equipment failure or a snapped wire. By staggering the wire slightly to the left and right as it moves between poles, the wire "sweeps" across the entire width of the pantograph as the tram moves forward. This ensures that the carbon strip wears down evenly across its entire surface, significantly extending the life of the equipment and reducing maintenance costs. This simple bit of engineering is a global standard for electrified rail and tram systems, ensuring that the friction is distributed across the largest possible area, much like how rotating your tires ensures they wear down evenly on your car.