i think with shy people it's all about the body language. he might not be too chatty but he can't disguise his actions. see if he's leaning in towards you when you speak, things like that. And would you travel with someone you didn't care about? :)
Asking him is a good way. Confessing to liking him first helps. I doubt he would travel the world with you if he wasn't interested.
he.ll travel only if your on a team but will not talk to you. shy people only say one word ya ya
Flash a ni pple.