I think that somehow you attracted to witness that first accident (maybe deep down you are terrified of car accidents). After that your thoughts probably got so caught up on that image that you attracted the other two as well. For example a few months back, my mom asked me to pay a car bill (which was 240 euros, so.. ouch!). I was pretty upset about it because I had some money issues. Anyway, I think I got so caught up on that, that a few days later I received not one, but two other completely unexpected bills (50 euros each!) from the country I used to study in last year.
Maybe your belief, that life is short attracted this? You believe it is short, so you attract the proof, that it is so.
Life is neither short nor long, it just is. Life is perfect the way it is. It is a game, and every game is a valuable experience -longer or shorter. We are eternal (not our bodies, of course) -so what does it matter how long this particular game is?
If the Universe really wants to draw your attention to something, it will show you the same thing 3 times, usually in quick succession. With accidents, you have to look at the symbolism of what they are REFLECTING BACK TO YOU?
Are you living your life how you want to, or by default?
Do you feel peaceful or composed in your life, or do you feel that things are out of control at the moment?
Are you beating yourself up at the moment about something? (Being angry or self-critical?)