Yes, definitely. This is a handy evangelistic conversation starter tip. It works whether the person is sitting down or walking by, go up to the person and say:
"Can I ask you a question? A deep question."
Wait for the person to stop or if he is already stationary, wait for him to look at you. Then say:
"What do you think happens after you die?"
And you are into a conversation. Always keep your tone friendly. If the person says, "I don't know" (a very common response), you could say "Do you believe there is a God?"