Danger!

Joke: You are in a car travelling at a constant speed. On your left is a valley, and on your right is a fire engine travelling at the same speed as you. In front of you is a galloping pig which is the same size as your car, and you can't overtake it. Behind you is a helicopter, flying at ground level; both are travelling at the same speed as you. What must you do to get out of this highly dangerous situation?