The 1947 Act, in effect, nationalised the right to develop land. It required all proposals, with a few exceptions, to secure planning permission from the local authority, with provision to appeal against refusal. It introduced a "development charge" to capture the planning gain which arises when permission to develop land is granted. This was abolished by the 1954 Town and Country Planning Act passed under subsequent Conservative government. Green belts were added in 1955 via a government circular. Furthermore, the 1947 Act introduced a requirement, which still exists, on local authorities to develop forward looking policy documents such as Local Plans or Unitary Development Plans to outline what kind of development is permitted where, and to mark special areas on Local Plan Maps (today referred to as policies map). It did not introduce a formal system of zoning as used in the United States. Counties developed Structure Plans that set broad targets for the wider area. Structure Plans were always problematic and were often in the process of being replaced by the time they were formally adopted.