To enhance your own safety and that of your passengers, rub a drop of olive oil or some other some protective oil on the seat belts, and then wear them.
Prayers may be offered to the Madonna, San Michele Arcangelo, Santa Rita, or to others.
Myth's notes:
Obviously, this charm, designed to protect people riding cars, is a product of modern folk magic. It is an interesting mixture of Catholic devotion (the blessed palm leaf) with a bit of old time Italian practice (the phallic corno).
Incidentally, little plastic red peperoncinos now frequently adorn Italian key chains and car rear view mirrors, serving as good luck charms. Apparently, this modern charm involves the same sort of protective blessing.