Have you ever thought about them much? Do you think they just happen? I for one believe most of the accidents started a long time before the actual event. Just small little mundane things that no one would even think about as causing an accident, and surely not something one would stop and think about causing a car crash in the future. But face it. Things do lead to accidents. Here are a few obvious ones. Someone gets thier drivers license. You get in a car. Oh but you got your license years ago and have gotten into the car many times and had no problem. OK let's go a little further to things one may not notice. Because you have not had an accident, or even a close shave, you have probably become to relaxed in your driving, started taking it for granted that you can get from point A to point B without even waking up. Perhaps you could, but remember there are other people out there. What do you mean you forgot about the other people?
Then your car itself ain't no spring chicken. Yes you keep the fluid levels up. You keep the oil changed. But do you or anyone ever crawl under the thing and give components a good shake just to see if anything is loose? Do you look around it every now and then to see if all the lights are working? Do you ever inspect the wipers, or do you wait for that first rain and then discover the blades need replacing or they just don't work. Or do you just jump in, start it up, and drive off thinking the thing is in as good a shape as it was yesterday?
Now, how about your disposition? Had a fight with your better half? Got fired from your job? Just fired someone? IRS just took your house? Or you preoccupied with thoughts of your up comeing vacation?
So when you and that other driver meet in the middle of that intersection, you look back and say "WOW. This accident started two days ago."