What a Black Box Data Dump Looks Like 643
An anonymous reader writes "Massachusetts Lt. Governor Tim Murray recently crashed his Ford Crown Victoria while reportedly traveling 108 mph. The car was pretty much shredded, but Murray walked away without major injuries. According to data from the car's black box, Murray and the Crown Vic experienced the equivalent of 40 gravities during the crash. The data contradicts the story he gave police. Maybe we should strap black boxes to all our politicians."
108? Typical /. bull (Score:2, Informative)
The investigation showed Murray was driving 75 miles per hour in the seconds leading up to the crash, which occurred before dawn on a stretch of Interstate 190 in Sterling. But his foot fell harder on the car’s accelerator, increasing his speed to 108 miles per hour as he slid off the roadway and into a rock ledge, flipping twice. His speed was recorded at 92 miles per hour upon impact with the ledge.
Re:40 gravities? (Score:5, Informative)
And what do you think the G in G-force stands for?
http://en.wikipedia.org/wiki/G-force [wikipedia.org]
1G is equivalent to Earth-normal gravity (an object at rest on the planetary surface). 40G is equivalent to 40 times Earth-normal gravities. Gravities is commonly used when discussing force related to multiples of Earth-normal gravity.
Not a great example of a data dump (Score:5, Informative)
It seems, looking at the raw data, that while "40G's" is quoted by the summary, and words like "totalled" are used, the data recorded by the box only shows a 15MPH crash.
There is other dubious data - for example, the box sensors indicate that the box accelerated by 22MPH while the data was being retrieved - ie. while sitting on some investigators desk - seems unlikley!
The crash acceleration data itself contains some very high amplitude high frequency oscillations - with a frequency around 200Hz. These are much bigger than the crash itself. That could be vibrations going through the car after something goes "twang", but could even be the stereo bass turned up loud. These vibrations are where the "40g" comes from - the actual crash is more like 1 or 2 g.
Note however there may be more information that wasn't recorded.
Re:Advice (Score:4, Informative)
I know people who leave their seatbelt connected 24x7 and just sit on it. I don't ride with them.
Re:Advice (Score:5, Informative)
Why people go so far to avoid wearing a seat belt is beyond me.
Re:Advice (Score:5, Informative)
You are missing the point. I DON'T have to say anything, or prove anything, It is my right to be silent and to not incriminate myself. It is their duty to prove me wrong. If they refuse to pay without reason/facts, then i will sue them. End of story.
You're right. You don't need to say or prove anything when you make a claim. They also don't need to pay your claim. If you believe that they do need to pay your claim and you sue them, then you WILL have to testify and give evidence. A lawsuit is a civil case. It is not a criminal case. The right not to testify only applies to criminal cases.
Please enjoy getting to pay to have your ass handed to you.
Re:Engineering (Score:5, Informative)
Re:insurance liability (Score:4, Informative)
I can see the insurance companies now: "Sorry Mr. Smith, but the speed limit is 60 and you were travelling at 61 so we are denying your claim."
No insurance policy that I'm aware of excludes coverage if you're speeing. I'm not even sure that's legal.
Insurance will also cover you if you're committing a felony DUI or driving recklessly.
They may cancel your policy afterwards and refuse to write you a new policy, but they won't refuse to cover you just because you were going over the speed limit at the time of the accident.
Re:Advice (Score:5, Informative)
DOT approval isn't a one time thing - i.e 1960 seat belts are fine, in a 1960's car, but not approved for a car built after the shoulder strap requirement was added.
Re:Advice (Score:5, Informative)
California and most other jurisdictions would imply that the intentional destruction of the black box would indicate that you knew that it had information that would have harmed your claim.
California Civil Jury Instruction 204 states:
"Willful Suppression of Evidence You may consider whether one party intentionally concealed or destroyed evidence. If you decide that a party did so, you may decide that the evidence would have been unfavorable to that party."
California Evidence Code Section 412 states:
If weaker and less satisfactory evidence is offered when it was within the power of the party to produce stronger and more satisfactory evidence, the evidence offered should be viewed with distrust.
California Evidence Code Section 413 states:
In determining what inferences to draw from the evidence or facts in the case against a party, the trier of fact may consider, among other things, the party's failure to explain or to deny by his testimony such evidence or facts in the case against him, or his willful suppression of evidence relating thereto, if such be the case.
Also see Willard v. Caterpillar (1995), 40 CA4th 892.
Re:100mph and no seatbelt? (Score:5, Informative)
I think they buried the lead here... 100mph, sans seat-belt, and he walked away? That's goddamn incredible. I've seen first hand what an accident at 170km/h looks like (on the Autobahn) and walking away seems basically impossible.
You have to be impressed with the performance of the air bag system. The logging shows the seat belt unbuckled, and the air bag controller firing the first stage charge, then the second stage charge 10ms later as the system detects a severe crash.
The accelerations indicate the car first hit something that didn't stop the vehicle. Then it hit something hard, but either bounced off or broke through. That's the brief 40G spike. (Football players experience 40G spikes in normal play.) Then there's some banging around.
Understand that this is just the airbag's record. All the airbag controller has is some accelerometers and seat belt information. Airbag controllers record that data primarily to improve the performance of airbags. [brpadvancedairbags.org] In the early years of airbags, there were a very few incidents where airbag deployment caused fatalities. (The worst it ever got was 0.5 fatality per million years of car registration.) This was essentially fixed (down to 0.01) by 2003. About a second of data is kept at all times, and shortly after the airbag fires, that data is locked in memory. Note that there's only 712ms of history here. The deceleration of 23MPH during airbag deployment is about typical for a crash that didn't involve hitting a solid obstacle like a bridge. The airbag has to fire at just the right time to be most effective, and the two-stage systems have to react properly to accidents of various types and severity. Here, the airbag system did exactly what it was supposed to do, and the driver walked away from the crash.
There's no vehicle computer data in the report. Vehicle data has more data sources and much longer term.
Re:Engineering (Score:5, Informative)
I don't think you understand what makes a car safe. You don't want something that is indestructable. You want something that dissipates a majority of a crash specifically by destructing. Previously, vehicles weren't designed to do this, and so the weakest area was the cabin. Now, they're designed to do that, and the cabin usually remans the most intact part of the vehicle, while most of the crash energy goes in to "shredding" (to use your terms) the rest of the vehicle. Ever seen an F1 crash? The reason they typically survive is that all that energy goes in to making the car practically disintegrate...
Re:Engineering (Score:4, Informative)
It actually has more to do with the size of the tires and the beefiness of the suspension/steering. The land-barges actually do pretty well at high speed (though the steering feels like mush). It's the very small econo-boxes with thin, low rolling resistance tires and small suspensions which start to feel out of control by the time they hit 100 mph.
Front wheel steering is dynamically stable - you can let go of the steering wheel and the car will naturally straighten out (wheel alignment problems excepted). Without getting into a full-blown essay on dynamics, it has to do with the geometry of the wheels relative to the body - try pushing a bicycle forward vs. backward. When going forward, slightly turning the steering wheel results in the body following in a way which straightens out the steering wheel. When going backward, slightly turning the steering wheel results in the body turning in a way which makes the steering wheel turn even more.
As you increase speed, the forces that imperfections in the road impart onto the wheels increases. The smaller wheels with less mass and the smaller suspensions with weaker springs will, at a lower speed, hit the point where these forces overcome the dynamic stability of the front wheel steering configuration.
Re:Does the data reflect tires slipping on ice? (Score:4, Informative)
One of my younger brothers for years refused to wear a seatbelt because he thought it'd be safer to be ejected from the vehicle in case of a crash. This despite me trying to tell him about the higher chance of getting crushed if that were to happen. He just wouldn't believe it or whatever.
Then one of our best friends from grade school was partially ejected from a pickup truck during an accident. The truck rolled and he was cut in half just below the rib cage by the roof. I've never seen my brother not put on his seat belt first thing since then.
Not everyone that isn't wearing a seatbelt gets ejected, and not all ejections are full ejections. I've seen lots of pictures during first aid training courses where people got partially ejected and scalped in the process by hitting something on the way out, or when being pulled back in.