以前的研究主要集中于宏观模型，讨论交通流量及密度的变化。

In the past, the hot point is the macroscopic model, which discusses the relationships among the traffic stream variables-speed, flow and density.

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随着我国城市化机动化进程的进一步加快，城市土地利用趋向于高密度集中开发，交通压力越来越大。

With the mobility of urbanization in China to further accelerate the process, urban land use tend to focus on high-density development, and traffic pressure is increasing more and more.

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