A utility may install many more fibers than it needs for its internal communications both to allow for future needs and also to lease or sell to telecommunications companies. Rental fees for these "" (spares) can provide a valuable source of revenue for the electrical utility. However, when rights-of-way for a transmission line have been expropriated from landowners, utilities have occasionally been restricted from such leasing agreements on the basis that the original right of way was only granted fo.