How long do I have to wait for the next bus?
下一趟车要等多久才来呢？
About 15 minutes. There is a bus every 15 minutes.
大约15分钟吧。每隔15分钟就有一趟车。
When is the next train?
下班车是什么时候？
When will the next train leave?
下班车什么时候发车？