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What a Black Box Data Dump Looks Like
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."
So, the first thing you should do after a car accident is to find and destroy its black box, so your insurance company would have no way to avoid paying the, what, insurance?
Some luck was involved, but anything that and car that can handle a crash at 108mph ( a bazilion kph for those of you out of the US) is damn amazing. I love engineers. They have made our lives so much better and are so unappreciated.
If he was going that fast, he'd be dead. He didn't have a single scratch on him at the press conference. If the tires spin out on black ice, does the black box adjust for that? or would it just assume he's actually moving at the rate the tires are spinning?
Maybe we should strap black boxes to all our politicians.
Explosives would be far more beneficial to society in general...
The black box is hard mounted to a solid part of the car. The black box and associated accelerometers stop hard.
A person in a seat, surround by air bags and wearing a seat belt does not stop nearly as hard.
Now if there had been no seat belt and no air bags .....
And what do you think the G in G-force stands for?
http://en.wikipedia.org/wiki/G-force
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.
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.
There's a disclaimer right there on page one:
Accident reconstructionists must be aware of the limitations of the data recorded... should compare the recorded data with the physical evidence...
Those disclaimers do mean things. The data was never intended to be used as a "black box"; That's purely media hyperbole comparing it to what's in an aircraft, which is designed to aid in accident reconstruction. The courts routinely dismiss GPS tracking data on phones used as evidence that the driver wasn't speeding because the device isn't meant to be used for that, and isn't precise enough anyway. An officer's radar gun, however, is.
That said... let us all look to the sky now and return to mumblings about conspiracies between or about the government and/or insurance companies.
#fuckbeta #iamslashdot #dicemustdie
At a auto racing school I attended, the "If you know you're going to crash" advice was to cross your arms on your chest and go limp. A death grip on the steering wheel is a sure way to break your elbows.
They will ask Walmart for video footage to identify who bumped into your car and drove away.
At least that's what the insurance told my wife once...
I need fore and aft GoPro cameras in my car - record my drives. What amazing things I could turn over to the CHP! The people passing on the shoulder, tailgating, yakking on phones. putting on make-up, shaving, picking noses...
STOP S.T.A.L.K.I.N.G MY WIFE!
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. 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.
Sure, seatbelts and airbags save car drivers -- which is why I am against them.
As a pedestrian, cyclist and motorcyclist, I think that ANYTHING that increases car driver confidence is... bad.
Get rid of seatbelts. Get rid of airbags. Put broken glass into the dashboard.
That should act to straighten out a lot of car drivers!
And, who knows? Maybe the additional care will balance out the removal of protection; hey, we may even have a reduction of fatalities.
Smear a bit of blood on the glass in the factory, just to be sure to get the point across.
Just another "Cubible(sic) Joe" 2 17 3061
I disagree.
Unless you live at the end of a road and can therefore perform a proper balls-out drag launch from your garage, backing out is always better. It prevents the assailants from munging up the front of your car (no chance for the hood to obscure forward visibility) as you roar over them, and offers reasonable protection against the hollow-point bullets that such people are likely to be firing at that time without endangering any critical engine parts (which, at this point, are just as valuable as you are).
And reverse is generally geared lower, which allows for quicker acceleration in the first few critical seconds.
After all that, you've got choices: You can just make a quick partial J turn of the correct angle for the street in question and get the hell out of there driving forward (with little loss of momentum if executed correctly). Or keep reversing down the street while firing madly with your left hand hand, and either execute a high-speed J turn where appropriate, or a slower 3-point turn if conditions allow.
Choices are always good.
If overall speed in reverse is an issue, simply don't let it be: Mercedes-Benz has transmissions with two reverse gears for a reason and if you don't know that, you're just not doing it right.
Kid-proof tablet..