Okay, crazy thought, but what if she caused the traffic accident? Like, she may not have driven the car, of course, and she didn't cross the road haphazardly, but what if she was crazy enough to try and get hurt for him to save her? Or even worse, she pulled him into traffic, trying to pull a double suicide because 'I want you to be mine forever, so let's die together' logic, but he managed to push her away at the last second.
I may have read too many mangas to come up with all those ideas, but you can't deny those things are possible.