main stream line

例句：

1. 1. The main stream line runs through the city center.
   这条主要干线穿过市中心。
2. 2.The new highway is a major improvement on the old main stream line.
   这条新高速公路是对旧主要干线的一次重大改进。
3. 3. The construction of the main stream line has been delayed due to weather conditions.
   由于天气条件，主要干线的建设已被推迟。