the urban population has increased rapidly since metropolitan areas and large cities have grown in size and urban challenges have risen in number and complexity these changes demand adaptable planning instruments however the complex administrative procedures for approving or amending regulating plans and the number of documents required when submitting them result in lengthy and intricate administrative and political processes and raise several challenges in the case of the prc the documents to be presented and the number of steps for approval are the same regardless of whether the proposal is a new plan or an amendment to an existing plan approximately twothirds of chile s municipalities are either developing or amending their plans see table