Maybe he noticed you mauling his crotch with your eyes and got a little apprehensive.

Look at it this way. He probably has a girl and ur sobeautiful that he has to stay away to control himself

Sitting down is tiring for him

Many times I personally stand for my stop, even if the ride is 30 minutes long... don't be offended.

smiling might hav seemed a lil creepy to him? just a thought.

¿Tu erès fea?

Sounds like you looked way too approachable... almost creepy. I wouldn't want to sit by you either, if I thought you were going to pin me down and give me a reason to pay you child support each month. Yeah. Honestly, I'm kidding, but not about looking creepy. If he thought you were unattractive but you looked indifferent, he probably would have sat by you. Though, since you obviously thought he was 'cute', he didn't want to make himself available. That's my take on it.

what if he is one of those guys who are scared to talk to girls and try to avoid any conversations :p think of other possible reasons other than urself :p

He's a loser, he rides the bus. You need someone that has a car

Probably he's afraid he's too fat and can't fit in the seat?