A Utilior is a utility corridor built underground or aboveground to carry utility lines such as electricity, water and sewer. Communications utilities like fiber optics, cable television and telephone cables are also sometimes carried. They are most common in very cold climates where direct burial below the frost line is not feasible (like in Alaska, where the frost line is more than eighteen feet below the surface and is frozen year round. They are also built in places where the water table is too high to bury water and sewer mains and where utility poles would be too unsightly or pose a danger (like in earthquake prone San Francisco). These tunnels range in size from just large enough to accommodate the utility being carried to very large tunnels that can also accommodate human and even vehicular traffic.