This question already has an answer here:
I work with someone that I've heard is thinking about asking to carpool with me and one other colleague (who I live with). The issue is, essentially, that we don't like the guy for various reasons which aren't really relevant. Both of us are polite to him at work, reasonably happy to talk to him if we see him at lunch, however being locked in a box with him for an hour each day wouldn't get each day off to the best start.
I don't think it would be particularly out of our way, and if we actually got on well, its something that I'd be happy to do, as I believe he lives nearby.
How do I go about resolving this in a professional and kind manner, if he does ask?