An air bag seems simple: When you crash, the bag quickly inflates so that your forward momentum gets arrested by a soft pillow of air instead of the dash, the windshield or the steering wheel.
Take all brain injuries seriously. Let's start there because the following will address the symptoms of a severe TBI, as opposed to a more mild TBI. But that is not to say that you should ignore mild symptoms and not get medical help. All brain injuries can have lasting ramifications and this is never something you want to take lightly.
People often think that they're skilled enough to drive faster without actually increasing the risks that they face. That's why so many people break the speed limit. They don't see it as gambling with their lives as they try to get to their destinations more quickly.