Germany is a federal, parliamentary, representative democratic republic comprising sixteen constituent states covering 357,022 km2 (137,847 sq mi) with a population of 83.7 million. Urban transport plans have been common in most cities since the 1960s. Although they are not legally binding, most cities and urban regions are developing such plans as an important part of general land-use planning. Elements of SUMPs are increasingly included in most plans but other planning documents often have different objectives.