他们决定将单轨铁路改为双轨铁路。

They decided to convert the single track railway to a double track railway.

双轨铁路可以减少列车的等待时间。

A double track railway can reduce train waiting times.

双轨铁路的建设需要更多的资金和时间。

The construction of a double track railway requires more funds and time.