subway/shuttle on shabbat

Question

Hi Rabbi -- If there is a free shuttle somewhere that takes people on shabbat can it be used. To get on all you have to do is show your University ID card. The shuttle is intended to take students to football games, but the football games happen to be close to YU, can I ride the shuttle to get to YU?? On a similar note, If I buy a subway token before shabbat, then, on shabbat, give the token to the person at the booth, who then opens the handicap door to the subway (she does this by pushing a button which unlocks the door -- its electronic) -- Can I then ride the subway on shabbat?? Is there any way in which I'd be able to ride a subway on shabbat?? It seems it is somewhat similar to the elevator question. Taking a subway to go to a shul that i like or to eat at a friends that is far away -- is that Tzorech? Does it matter if its FREEZING out (its ridiculously cold in NYC now!!) Thanks as always Rabbi!