Lugging those rolling backpacks up stairs is hard, man.

(pffff).

Perhaps a polite "excuse me" would be a sufficient remedy?

These are students, not elderly people, and I don't have the confidence to speak in public. 

Well, why expect someone to be willing to put in the effort to speed up if you are not even willing to put in the effort to speak up and ask?

Confidence doesn't just magically appear out of nowhere. And when you're in a building crammed with students, you should be aware of how busy and congested the stairs and corridors can get - everybody in modern times been stuck in a queue or traffic of some sort at least once in their lives. There's also the fact that these are students. Many students are loud and talkative. Seemingly extroverted. An anxious and impatient introvert is not going to suddenly gain confidence to ask people they don't even know. 

You have to be conscious of your surroundings and where you are. Why expect that everybody wants to be as slow as you are? 

Requirements for being a student: 

1. Must be able to run. 

2. Must be able to elbow way past other students.