renamed Neighborhood Service Centers (NSCs) and were placed under the jurisdiction of the Department of Neighborhoods. More recently, their number has been reduced. As of 2011, there are NSCs located in Ballard, Lake City, the University District, the Central District, West Seattle, Southeast Seattle, and Delridge. Local improvement districts A local improvement district (LID) is a method by which a group of property owners can share the cost of transportation infrastructure improvements. This involves improving the street, building sidewalks and installing stormwater management systems. Without Seattle's LID assessment system, the city would be unable to maintain its rapid growth in population and territory. LIDs have helped define neighborhoods by localizing decisions about issues like sidewalks, vegetation and other features of the public space, permitting neighborhoods to remain distinct from their neighbors. Informal districts No official neighborhood boundaries have existed in Seattle since 1910. Districts and neighborhoods are thus informal; their boundaries may overlap and multiple names may exist for a single district. Boundaries and names can be disputed or change over time. In 2002 a Department of Neighborhoods spokeswoman said, "I've seen my area go from the 'CD' to 'Madrona' to 'Greater Madison Valley' and now 'Madrona Park.' " Some neighborhoods, such as northwest Seattle, do not have widely recognized names for their greater districts. Throughout Seattle one can find signs indicating the boundaries of neighborhoods; the locations of these signs have been specified by the city's many community councils. However, the boundaries suggested by these signs routinely overlap and differ from delineations on maps. For example, signs indicate that Lake City Way NE is the southeastern boundary of the Maple Leaf neighborhood, while the city clerk's archival map places that district's southern boundary at 85th Street. Another example of boundary ambiguity is "Frelard," which local residents call the area shared by Fremont and Ballard between 3rd and 8th Avenues NW. Signs facing opposite directions on NW Leary Way reveal the overlap. Further difficulty in defining neighborhoods can result from residents' identification with neighborhoods different from those marked on signs and maps. After an acrimonious development dispute in 1966, a group of concerned Wallingford citizens enlisted the University of Washington Community Development Bureau to survey their neighborhood; the survey revealed that more residents of southwest Wallingford considered themselves citizens of Fremont than of Wallingford. Transportation Minor arterial roads are generally located along the boundaries of neighborhoods, with streets and highways