Slashdot Mirror
Washington Finds Computer Simulation Unreliable
Toadpipe writes "Washington State Court of Appeals reverses a conviction in which a computer simulation had been the main evidence. Quoting 'At issue was PC-Crash, a computer program distributed by Vancouver, B.C.-based MacInnis Engineering Associates. The program recreates traffic collisions using simulations and reconstructions.
"PC-Crash had not been validated for the purpose for which the evidence was offered, simulation and prediction of multiple-occupant movement within a vehicle during a multiple-collision accident," the Court of Appeals said in ordering a new trial. "There is no general acceptance in the relevant scientific community of the use of the PC-Crash program for the purposes to which it was put."' Here is
the Court's opinion."
Are they going to stop accepting my Grand Theft Auto murder re-enactments?
So I can't get a pilot license just for playing with Flight Simulator?
Was this a MicroSoft product by any chance?
In other news, the Oval office informs all good citizens of United States that Kyoto computer simulations are no longer valid.
This is my opinion. Everyone has a right to my opinion.
uncertified.
Anyone can say that they're an expert. The court system requires that if you're going to present evidence, you better have some credentials. This program, apparently, did not have the proper credentials.
Every part on a car would need to be tested for strength, width, height, depth, shape, mass, the connections holding it to another part, and that bolt tested...You get the idea. You would also need the conditions that happened the second the crash occured. Road type, amount of friction, temperature, slope, etc. As a juror I would never trust a computer simulation.
My PC crashes quite reliably actually.
99 bottles of beer in 175 characte
I'd like them to stop accepting photo radar data. The cities in my area have switched to digital photography. Currently one's only out is to request the Plaintiff to produce the calibration records for the system for the day of the ticket and hope that they don't have that data.
I'd be okay with photo radar and with red light cameras if they were used to bolster the Prosecution/Plaintiff, like if there were a car accident and the red light camera data were used to show that the cited person (by the officer on the scene) had indeed run the light, and that the officer was correct. The current system of using photography with near-automatic conviction deprives people of privacy. If the police want to cite people for speeding or for any other traffic violation then they need to get out there with people who will be required to testify as to what they saw; people who actively claim the count in the charge, not some computer or desk-jockey who analyses data after the fact.
Of course, I also have the opinion that if there's no victim then there's no crime. Take this as you will.
Do not look into laser with remaining eye.
I know, I may have to turn in my /. account.
/sarcasm off
I would like to see more of this kind of common sense in life today.
The story states both occupants were ejected from the car in the accident. The prosecution is quoted as saying their key element of the case was that part of the passenger door was melted on the dead guy.
So which was it? Did the dead guy stay there and take the burn, or get ejected? Did the car sit for awhile burning, and take off again?
I will make the specific conclusion from the vast amount of data in the article that there was enough doubt to go around in this case.
To often attorneys for both sides put up a George Lucas light show in order to sell their version to a jury. Matters are not helped by the fact that jury selection all to often resembles a Jerry Springer casting call.
I've seen the software in question used in a trial (once). What I saw seemed to be a believable representation of an elastic collision between vehicles. At no time were there any renderings, or mention of what happened INSIDE the vehicles. But then again, you know what they say about prepared demos...
Even the summary belies the headline (and the article torpedoes it). The conviction was overturned because the software was not validated for the use for which it was used. The court made no comment on its reliability...they left that up to the scientific and engineering community. Based solely upon the court's comments and the article, it sounds like a good decision to me.
=h=
I have a more general problem with red-light radar (and most red-light radar) - it's "teaching to the test." Or in this case, "enforcing laws that are easily mechanized, not laws that are most critical to public safety."
The biggest problem I face on the road are tailgaters and the guys who cut me off at interstate speeds and the morons who barrel out of parking lots at 20 mph without checking for traffic and the idiots who think "right turn on red" has right of way over people already on the road. Hell, even the superjock riding his bike far too fast for me to see him approaching as I cross the bike path... and he wrongly believes that he, not I, have right of way. (Pedestrians do, but in this state mounted bikes are "vehicles" and bike paths are "secondary roads.") As if it will matter when he hits my car (or vice versa), other than me suing his estate to repair my car's paint job.
People who run red lights or are speeding between lights on limited access roads? Not A Problem. Maybe once every few years I'll nearly get clobbered by some moron who goes through an intersection at high speed long after the light changed, but that's reckless driving, not merely running a red light. The latter should remain illegal, but a low enforcement priority unless it's an ongoing serious problem at a specific location.
So why do we see more and more red-light X systems? Because they're cheap revenue sources. To actually make driving safer you have to hire more cops and put them in more unmarked cars and get them out on the street where they can nail the guys who really are hazards to other drivers. Not guys going 45 in a 35 zone because that's what the heavy traffic is doing and it would be far more dangerous to obey the law than to break it. Or the guy who's behind a truck and doesn't know the light has turned red until he's already in the intersection.
How long until the laws themselves are written on the basis of what's easily enforceable, not on the basis of what harms others?
And the guy in Denver who put a photo-radar system on the interstate onramp where traffic is always at least 15 mph over the posted speed limit? The cop who lectured my HS class wants to talk to you - he assured tens of thousands of us that no cop would ever, under any circumstances, ticket us for going over the speed limit in order to merge with traffic. (We were supposed to gradually slow down once merged.) Ticket or being flattened by a semi? Hmm, which will it be? Ticket or being flattened by a semi. Gee, that's such a hard decision. Not.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
"As you can see from this computer simulation, the driver was in fact distracted by the 20 foot high Blue Screen of Death standing on the opposite corner of the intersection..."
Task Mangler
In related news, the Slashdot community have dismissed the post's title - "Washington Finds Computer Simulation Unreliable" - as being inconsistent with the article, or indeed even the summary of the article directly beneath the title.
At issue was the word "Unreliable", which implies some comment on the accuracy of the software in question. The article, however, consistently states that the software "had not been validated for the purpose for which the evidence was offered", a far more sensible claim.
"Titles of Slashdot posts have not been validated for the purpose for which this one was offered, simulation and prediction of the content of the article itself," a Slashdot representative stated. "There is no general acceptance in the relevant online community of the use of article titles as a substitute for R-ing TFA."
CowboyNeal was not available for comment.
This may be shocking, but I am actually familiar with both this software and the process of giving expert testimony. PC-Crash is one of several *Crash* programs provided by different vendors that share a common lineage. It and its sister programs are used extensively in accident reconstruction and the results are presented to juries every day. The core of these *Crash* programs are a series of well-established (although certainly not perfect) algorithms and physical properties related to vehicle dynamics. The problem here was the extension to occupant dynamics, not the use of simulation programs in general.
You may now return to your regular uniformed ranting.
You cannot, even in theory, predict how a human with arms and legs banging around will move in a complex crash. It's chaotic, in the formal mathematical sense of the world. That is, an arbitrarily small change in the initial conditions can create a large change in the outcome. In Falling Bodies, if you change the low order digit of a double precision number in the initial conditions for a fall down a staircase, the simulations will start to diverge after about a second, and the fall may end quite differently.
I had this discussion a few years ago with an Army officer who was trying to reduce accidents in parachute landings, and was considering using Falling Bodies. I talked him out of it.
Auto collisions can be simulated well because there's one big mass that dominates the simulation. So you get a deterministic result within some error limits. Multibody systems with joints and links are quite different.
Realistically, you can probably do a sound simulation which predicts how a passenger will bounce around from the beginning of the collision to the first passenger interior collision with the vehicle. Beyond that point, forget it.