In the U.S. state of Pennsylvania, state highways are generally maintained by the Pennsylvania Department of Transportation (PennDOT). Each is assigned a four-digit State Route (SR) number in the present Location Referencing System. Traffic Routes are signed as Interstate Highways, U.S. Routes and Pennsylvania Routes (PA Routes), and are prefixed with one to three zeroes to give a four-digit number. PA Routes are also called Pennsylvania Traffic Routes, and formerly State Highway Routes.