What you really mean is “only if”, not “if and only if”. “B if and only if A” means that B ↔ A, while “B only if A” means that B → A (but not A → B).
(However, the real world implications assumed above are not correct – it is possible to be in a car crash as a passenger in a car, or as a pedestrian or bicyclist hit by a car. So neither A → B nor B → A is true in real life.)