the transitory nature of bus stops causes girls to give more approach invitations.
a specialized approach is not needed just because it's a bus stop. however i would be cautious about opening direct. if she has a bad reaction, and the bus isnt due for another 15 minutes, then thats gonna be a heck of a long wait!
if you're feeling shy, you can ask her if she knows when the bus is coming. you could also ask her if she's going anywhere fun