I could see the steep, long concrete stairs going down to the Long Island Railroad or up into the street.我能察觉向下通向另一个地铁站，向上通向街道的陡峭、长长的混凝土台阶。
这里是going down现在分词后置定语修饰前面的。我能察觉陡峭、长长的混凝土台阶向下通向另一个地铁站，向上通向街道。还是这里going down作谓语。怎么区分啊？