A utility tunnel, utility corridor, or utilidor is a passage built underground or aboveground to carry utility lines such as electricity, water and sewer pipes. Communications utilities like fiber optics, cable television and telephone cables are also sometimes carried. They may also be referred to as a services tunnel, services trench, services vault, or cable vault. Smaller size cable containment is often referred to as a cable duct, or underground conduit. Direct-buried cable is a major alternative to ducts or tunnels.