I was feeling taken for granted by a friend I meet up with occasionally for a meal - you know the sort who takes all the cash, including tips, that everyone else has contributed and then pays on her card, no tip! Which means she gets free food and drink! She always got a lift home as well. When just the two of us met up she behaved like this too so, on one occasion, I'd had enough and divided everything up according to what we'd spent and then asked her for the exact money (I'm usually quite happy to split the bill according to how many people are there, even though I don't drink as I'm driving). I then told her I couldn't give her a lift home but I was happy to wait at the bus stop with her until the bus came. We are still friends, as in all other ways she is a lovely, interesting person, which is my point really. If your friends value the lift more than your friendship, it isn't really worth going out with them any more. Perhaps they just take getting a lift home for granted as you've always done it. If you are uncomfortable driving them home maybe you could tell them in advance that you can't do it so that they can make other arrangements. You don't need to give them a reason.