Do u know this movie?

im tryin to find a movie i saw couple of years ago but i cant remember the name. its about some 18 wheelers that drive them selfs n they kill people n the cause was because of a green toxic cloud or someting. if u know da name plz can u tell me? o thers another one about a car that hijacks people it looks like an old plymouth or something at da end they blow it up by making it run off a clif if u know the name plz let me know tanx