Hi Rk,
I do not agree that valid Driver license would be fine.. make ur I-20 photocopy N If you have valid visa make a copy also N carry it with you... I live in buffalo. Its strict here u might face border patrol people asking for documents. My roomate when she was riding in greyhound, they stopped bus N check the documents of every people N one of the chinese gal didnt have and they take her somewhere n didnt let her go.
N she was also aked in peen station in NY.. heres also the link that i found in sajha a yrs ago. http://chronicle.com/article/Far-From-Canada-Aggressive/125880/?sid=at&utm_source=at&utm_medium=en
I also had such expereince when travelling in amtrak but i wasnt asked any documents ... It was a random check..
So.. I think u should carry .. but dont worry in MA coz its not strict but about RI, there is....
now its all on u... try to be in safe side ..