From the early 2000s when the China Expressway Atlas (CEA) began to distinguish National Main Routes from Provincial Expressways, and thereafter when 'Superior' Highways began appearing, they being better than ordinary highways, but perhaps not completely limited access or not fully divided four lanes. Note that atlases from the same year, as well as those with different dates, can display the same route as either an expressway or as a superior highway. Shapefile with attributes for highways between 1992 and 2010.