Wednesday, June 29, 2005

Accident Investigation

David asked me how long after the accident it took me to figure out what had happened, and I have to admit it wasn't until that evening when the eureka moment arrived. It was fun piecing together what I knew and suddenly realizing the accident sequence. I mean, I knew I was being hit by something: it made a loud noise, and I could immediately tell I was injured, but the what happened how took some deduction.

Everyone from the first fire department paramedic to the doctor was asking about my neck, but it was fine. People expressed surprise that I didn't have whiplash-type neck injuries. I've thought about it and realize that I sit very erect while driving, with my head already almost against the headrest, so there was no significant travel for my neck to whip through. My injuries seemed to have been sustained as a result of the second impact, on the car ahead. And what disturbed me was that I had no memory of seeing my car close in on it. I was asked "did you take your foot off the brake when you were hit?" Surely I would remember the sight of my car ramming another after I had come to a complete stop behind it, and would remember trying to brake, or honk a warning, or something. I just remember seeing the car ahead of me not pull away with the others when the light changed, and it was still a decent distance away from where I remembered my front bumper being located. I knew I was lucid and clear-headed. There was no way I had lost consciousness or had any memory loss. So why hadn't I seen myself hitting the car ahead? Did I close my eyes?

That evening I had someone help me inspect my more minor injuries. I had had my seatbelt on, of course, but I could find no bruising on my hips or shoulder: something you'd expect to find if I had been thrown forward hard enough to break my back. Had the inertial reel seatbelt failed? I've never liked those things. Give me a five point harness that I can cinch down tightly, and that holds me equally on both sides. But if the seatbelt had failed I would have struck the dashboard. I have no injuries on my chest or face. I do have cuts and bruises on my shins and knees, but the front end damage was not enough to compress the engine towards me.

I had assumed my spine had been compressed by being bent forward further and faster than allowed for by its design limitations. That's not what happened. The initial impact from behind slammed me against the back of my seat and broke it, leaving me flat on my back ramming the other car feet first. I couldn't see it because I was lying on my back, thinking "damn, I just got rear-ended." The concussion of the second impact was in line with my spine, travelling up my feet and legs. My car stopped and the car in front continued further, like two marbles trading momentum, and the force of the impact swung my broken seat back up a little so I could just see the car ahead.

It felt as satisfying as a good murder mystery to have worked that out. That's why there were broken pieces of plastic dashboard on the floor, and scrapes on my shins. My doctor says that's why my leg muscles are probably sore, not from the awkward way I've been walking. The human body can take a lot of G-force, so long as it isn't directed along the wrong axis.


Anonymous said...

Nice job putting that all together. I find it disturbing that the seat back failed like that -- that also made the seatbelt pretty ineffective for the second impact, I'll guess.

Are there going to be charges laid against the driver who hit you?

Aviatrix said...

That's what I thought about the seat, David, but everyone else seemed to think it unextraordinary. I guess we expect more of airplanes. The police and ambulance attendants kept mentioning that I had the seatbelt on--I think they have a box to tick on their forms about that, but I don't think the seatbelt made any differnce at all.

Unless the other driver was drunk, driving without a licence, or rammed me on purpose, I don't think there are charges that can be laid. It's not illegal to be a really bad driver in this province. His (the police report indicates him to be a 67 year old male) insurance rates will increase.

Avimentor said...

Some car manufacturers, like Volvo, actually design the front seats to fold backward during an impact from the rear to absorb the impact. I think Volvo calls it SIS - for Supplemental Impact System or something or other.

Not sure what the treatment recomendations are for a compression fracture, but after my back surgery the neurosurgeon and physical therapist both advised me to avoid prolonged sitting (more than 10 or 15 minutes at a time) during the healing process. For what that's worth ...

Greybeard said...

I attended the Army Aviation Safety Officers Course (whew!)
in 1981.
There, we learned much of the sort of thing you are looking at, but about aviation accidents......
Light bulbs that are burning during the accident sequence will be deformed in a different way than bulbs that are not lit.
Engines, propellors are damaged differently if they are turning, obviously.
If you find this sort of thing interesting, and think you could put up with digging through pieces of flesh to do your work, there is an interesting (and good paying) job waiting for you!

Aviatrix said...

Yes, Greybeard: I find that sort of thing fascinating. Reading accident reports was part of what got me into aviation, because I was enthralled by the level of detail and the obsessive refusal to make assumptions that characterizes the investigations. Then someone took me flying and I realized I had do that some more.