What is the most polite way to stop carpooling with someone?

My best friend and I have been carpooling for 3 years and 6 months ago (when gas prices were ridiculous) we were approached by another guy who works in our department. We both feel we have given it a 'fair shot' but he is really annoying and we really miss our 'girl chats'. How can we tactfully get out of carpooling with him?What is the most polite way to stop carpooling with someone?
Just tell him he will need to make other arrangements and say no more than that; you do not owe him any explanations and he has no choice but to accept the situation.What is the most polite way to stop carpooling with someone?
Exactly as you stated. You miss your girl chats and no longer wish to carpool with him. This way you are not saying anything offensive
Well, you could always just start making the ride unbearable for him. Drive crazy, smoke in the car, wear buttloads of perfume, fart, start making plans after work where he either needs to hangout with you or find a different ride.
Just tell him that you and your friend have had to make alternative arrangements because all three of you guys call pooling isn't working out anymore, if he presses for an answere just say its personal and you guys would rather not talk about it.
Been in that situation before, and believe me, it doesn't turn out as badly you might think. I just told the guy the truth, that I didn't want to carpool with him anymore because I didn't feel safe (he was always stoned.) He acted surprised, but there was no real harm done. Two weeks later he got fired, so I guess I jumped the gun a bit.