既有线提速，线路条件是最基础的。

So the circuit term becomes the most basic for the increasing of speed.

现行的既有线客运站通过能力计算方法不能直接用于客运专线客运站通过能力计算。

The calculation methods for the carrying capacity of stations of existing railway lines are inapplicable to high speed passenger railway lines.

根据京沪既有线能力现状，以先修建徐州至上海段高速线为有利。

According to current capacity of the existing Beijing-Shanghai Line, it is more beneficial to build the high speed section between Xuzhou and Shanghai first.

论文以此为出发点，对无砟轨道应用于山区小半径曲线既有线提速的可行性进行研究。

As this a starting point, the paper researched the speeding measure of the existing mountain railway with small radius curve.