Through analyzing the two common evaluation indexes of intersection traffic condition,consist of intersection traffic capacity and intersection saturation degree,and on the basis of determining service level of each directional traffic line,the feasibility of grade crossing be separated can be determined comprehensively according to the position of grade crossing in the urban density area.

This paper analyzes on the theoretical foundation of the tighten city morphology and the problems existing in it, and points out that only controlling the urban density in a rational scope could implement the sustainable development of the city.

On the idea of urban greening in compact city in China;

Having discussed the location theory of microeconomics and the worldwide experiences in urban density control, the paper introduces a rational approach to urban density zoning including three-level planning policies, and its application in the case of Shenzhen Special Economic Zone.