when's the next train?

What time will the next train leave?一般的话呢也会这么说,when does the next train leave?
因为此句所涉及的语法点是一般现在表将来的,主要表现在“来去动停”这类动词上,像"leave/open/arrive/start"等等一类的词,都用一般现在表将来,但是这个这样也是没错的.
至于When 's the next train?为什么不用will 也可以用啊,补全就是when will the next train leave?而When 's the next train?比较口语化了.