how to teach a teach a teen to be more cautious

My 14 year old son, who is really getting into mountain biking, rode through a stop sign without looking and was hit by a car.  Mercifully we were very very lucky and he was not seriously hurt.  He has always had the attitude that nothing will happen, that he doesn't really need to watch for cars etc.  He -seems- to have learned something from this but is still talking with a tone that he doesn't not need to be more careful.  ANY advice on how to approach this would be much appreciated.  I've seen articles about how at this age their brain isn't motivated by fear of something bad happening (or else humans would never have left Africa) and we don't want to discourage the exercise and community he is getting but that phone call from the fire department on the scene is not something we ever want to go through again.  Thanks!