zhè duàn / tiě lù / yǐ jīng / gǎi / chéng / le / shuāng guǐ / yùn shū / xiào lǜ / dà dà / tí gāo

这段铁路已经改成了双轨，运输效率大大提高。

This section of railway has been converted to double-track, greatly improving transport efficiency.