Urban planning in the United States is quite different from elsewhere. Since they are a federal1 democracy， they do not have the centralized national planning that provides the framework into which local planning must fit. It has not been popular to suggest this centralized approach since most Americans abhor2 big government. Thus， the 50 states emerge as the highest level for planning， and sometimes they are subdivided into regional planning areas.
Urban planning occurs at the city and regional level today. Many functions， such as transportation， water supply3， sewage4 treatment， pollution abatement5， and economic development， occur at the regional level， although no true general-purpose regional governments have been created. Instead， planning at the regional level tends to be advisory to the already established general-purpose governments at the state， county， and municipal levels. These levels have their own planning processes， which are often linked with regional plans. Urban planning will most likely remain a regional and local process for the foreseeable future. It is a continuous process that does not end with the creation of a plan but proceeds through the decision-making and monitoring6 and evaluation7 phases of government. And it has become established to the extent that it can be considered institutionalized. It has gone beyond the need to establish its legitimacy8 and has become an inherent part of government and business. The next phase in the evolution of planning will be implementation —— that is， ensuring that good planning will be carried out by both the public and the private sectors. This means that planning， while largely concerned with the built environment， will have to relate better to economic， social， and political conditions.
Urban planning can make no claim to solving all of societys problems， but it can be an effective and efficient process for building cities and their regions in the best way possible. Here， planning must be a subtle process that is open， participatory， and flexible. It requires both technical skills and the arts of compromise9， negotiation1~， and consensus. Urban planners in the modem world must be part reformer， visionary designer， and politician. From this evolution of urban planning there have arisen several long-term trends.
展开
