How do suspension bridges support a roadway with cables?

A suspension bridge supports its roadway by carrying vertical loads through curved main cables held in tension. These cables are anchored at both ends of the bridge and pass over towers, which transfer the loads to the ground through vertical compression.12

The roadway, or deck, is suspended from these main cables by smaller vertical cables known as suspenders. Because the deck hangs in the air, it must be designed with sufficient weight or stiffness to prevent excessive movement under loading. Engineers often use a web truss or box girder to provide this necessary rigidity. The entire system functions similarly to an upside-down arch in tension, where the towers act as the primary compression elements.321