I know that you can disable the carpool by selecting an owner of the car, however, I only have one car and 2 sims that I want to carpool to work together and neither of them own the car since the carpool option won't show up if one is the "owner." it's annoying for 2 carpools to show up when they are just driving into work together so is there a mod to disable the carpools from coming even if no one owns the car?

Not sure about a mod that disables the car pool; but there is a mod that adds flexibility regarding car pools here at MTS: http://modthesims.info/d/593810